Hey everyone, I am looking for some more brain power with this problem. Machine is a 120-2 with what I believe to be a 120-3 main control valve (mcv). This means it does not have the adjustable pressure regulator on top of the unloading valve like the -2. Its on the bottom instead. According to the manual the differential pressure (dp) sensor needs to see 370 psi or more to signal the pump to run at minimum displacement while at idle. This 370 psi is set by the spool and spring in the unloading valve. My DR.Zx shows that its making ~250 psi at idle and the angle of the pump is 6-7 degrees. If I unplug a sensor and get the machine to run at max displacement (24 deg) at idle, the pressure increases to 480psi. As far as I can tell this "base" pressure of 370 psi is set purely in a physical way by the unloading valve. There should be no sensors involved since the dp sensor is looking for 370 psi or more to set the pump angle to the minimum of 3 deg. I have tried shimming the spring in the unloading valve to increase the pressure but it made no difference. There must be some sort of internal leak in the mcv. The pump is brand new inside so I don't expect it to be weak. Any thoughts are apricated. Jason
@LACHAU ......Help!!!!!
Anybody? Thanks for the thread bump mg2361. I tried to pm LACHAU but I don't know if it worked.
Just a thought. I think the 370 psi is 370 differential, so if it is low (250), then maybe there is leakage somewhere allowing more pressure on the load sense side of the Dp?? Unfortunately, I don't know of any ports to actually test those pressures with a gauge. If there is leakage like I mentioned, then increasing pump pressure will increase load sense pressure so the differential will be the same??
Hmm, that does make some sense, I am going to try setting all the circuit relief pressures. Hopefully there is one that is bleeding off pressure. While the machine is idling I can hear a hissing noise coming from the main control valve area. It's not loud and it sometimes fluctuates.
1/- You should try to adjust the DP sensor (It's adjustable). 2/- I suggest you double check. That means you will use a differential pressure gauge to check if the value of differential pressure is correct as shown by Dr.ZX.
Could you please supply a picture/drawing of the port locations?
Hi LACHAU, 1) I have adjusted the DP sensor. I have a workshop manual for the excavator and in there it shows how to take apart the DP sensor and gives a specification for the adjustment. I attached a couple of pics. It said 0.4V so that is what I adjusted it to but I have read in different threads that some people are adjusting them at 1.0V - 1.4V. While adjusting it I put a smaller allen key into the hole in the end and pushed on the piston. If I pushed hard enough I could get the multimeter to read 4.5V. I also bought an aftermarket DP sensor, but when I installed it all the 5V sources for the other sensors went dead including the communication connector for Dr.Zx. When I changed to the old DP sensor all the 5V sources came back and I could get Dr.Zx to communicate again. It turns out that the new DP senor has a short to ground internally. The 5V source is going directly to the ground wire and leaving only 0.29V behind on the signal line. For some reason that affected all the other 5V sources on the machine. 2) I recently had the entire main control valve apart for cleaning/re sealing with new o-rings. If I remember right there were two plugs nearby the DP sensor. One above it on top of the mcv and another partially hidden behind the DP Sensor. I could be wrong. When I had it apart it was hard to tell if they would be useful or not. A diagram of some kind would be great!
Did the problem start immediatley after this? If everything was not put back together exactly as it came out this could be a cause of your problem. I had a valve bank resealed and one little piece was put in upside down and it caused a hair pulling scenario which I wont bore you with. Long story short it took a retired hitachi mechanic 3 days of running tests to figure out the problem. I ended up with all new sensors as well. The hydraulics on these machines are really finicky the way they are designed, everything has to be in order.
Hi timbercutter, The problem started before I took the mcv apart. I was very careful to put it all back the way it came out. I bought the machine with lots of issues and I am now at the point where most of them are fixed and this is the last major one. I am going to try setting all the relief pressures this weekend. According to the info I got from mg2361 this could be the problem. I find it funny how in the manual it says that when you take a relief valve apart you are supposed to measure the height of the set screw so you can put it back properly. The problem is that 1/8 of a turn is equal to 300 psi and the screw is fine thread. They could be way off and you wouldn't know by measuring let alone looking at them. I have not messed with the adjustments on the relief valves but it looks like other people might have been in there, so hopefully adjusting them makes a difference. Are you located anywhere near me? Would this retired Hitachi mechanic like to look at my machine? Joking, but kinda serious haha.
sorry for the late reply! I repaired these machines a long time ago! So it took me a long time to rummage through the notes!!! You measure the pressure at the place marked in the picture and compare it with the pressure of the main pump.
Where did you read that?? So have you tried adjusting to that value? It's been a really good experience. Try setting it to 1 Volt .
Alright, I set the dp sensor to 1.0V. At idle the pump angle used to be 6.7 - 7.3 degrees. After the adjustment the pump angle is 8.2 - 8.4 degrees. That's the only difference it made, the overall pressure did not increase. I believe the spec is 3 degrees at idle, (controls in neutral) and 5 degrees in P mode (controls in neutral). I pulled the pump angle sensor and turned it by hand. The full range from 0-24 degrees displayed on Dr.Zx. I hooked up a new angle sensor and it also went from 0-24 degrees. I installed the new one anyway. Unplugged the pump solenoids and let the angle fall to 24 degrees. Then set the angle sensor to 4.47V by back probing it. Fired the machine up and got the same 8 degrees at idle. I tried to to set the relief valves today. 1- turn up main relief a couple of turns 2- bring rpm to 1700 and oil temp to 50C ( I only got to 40C) 3- adjust circuit reliefs by holding each function over relief and then adjusting (1/8 turn = 300 psi) (measure at pump with gauge or Dr.Zx) 4- then adjust main relief back down to where it was My brother and I started making the adjustments but the pressure never increased. By the end we turned all the circuit reliefs and the main relief all the way in until the adjustment screws got tight and there was no increase in pressure from any function being tested. The only reliefs we did not touch were the swing motor and the travel motors. They were not part of the procedure mg2361 gave me. Should we do something to them also? - The gauge showed 3600-3800 psi (looking for 5000psi) - Dr.Zx showed 3000-3500 psi (21-24 Mpa) ( I have replaced the sensor, the old one read the same) - The lowest I saw was 2750-2900 psi (19-20 Mpa) when I tried to turn and the tracks stopped moving. Turning left or right has the same result. It will start to turn and then just stop, probably due to the very low pressure. I had all the shuttle valves apart when I cleaned and checked the mcv. They were all good. The diagram looks like it is pointing to the plug that covers shuttle valve #7. That plug only holds the shuttle valve in. How would I connect a gauge to that location? Thanks for your help LACHAU! I appreciate you taking the time to go through your old notes.
Still trying to track this problem down. In the procedure for setting the relief valves it only talks about adjusting the ones that are located within the main control valve (mcv). It does not mention setting the travel or swing reliefs. I also have information that says, if any of the circuit reliefs are set lower than the main relief, that circuit relief will then act as the main relief. That makes sense for the circuit reliefs that are located inside the mcv but what about the travel motors and swing motor? Will their reliefs affect the overall pressure if they are set lower than the main relief?
Only when the swing or travel are activated will their reliefs affect the system if they ate set lower.
Swing and travel reliefs are in the motors themselves and not in the main control valve.
Ok, that makes sense, just trying to cover all the angles. How do I go about checking the pressure at #7 shuttle valve? I am sure that it is just blocked off by a plug. There are two other ports that I will try to describe with pictures below. These are from when I took apart the mcv.
That plug next to the Dp sensor is connected to load sense pressure. There is a screen in there to keep any debris that may be in the load sense oil from contaminating the Dp sensor. Yes, that hose is the drain for the end of the Dp sensor and is not connected to any pressure.
Ok, I got a little side tracked and rebuilt all the circuit relief valves and the main relief valve. All of them are still cranked down all the way and the most pressure I can get in any function when held over relief is 3600-3800 psi. I still plan on checking the load sense port but it is blocked by the dp sensor body and will require a special connector or some creativity to get a gauge on it. I am coming back to the low system base pressure issue because it has got to be related to the rest of it. I back probed the dp sensor plug with the machine at idle and the controls in neutral and got 2.8-3.0V. It should be 4.5V with all the controls in neutral. The picture below from the manual explains it pretty well. I took a jumper wire and jumped the 5V source over to the signal line that goes back to the pvc controller. As soon as I touched the jumper wire to the signal line I could here the engine idle smoother and the pressure line flexed so I know the pump was being de-stroked. I believe the dp sensor is working fine. According to the manual the pressure at idle is set by the unloading valve at 370 psi. DrZx shows the pressure to be 1.6-1.9 Mpa (230-275 psi). I have a gauge plumbed in at the pump also but the needle barely moves. It is a 0-3500 psi gauge so I should be able to see 370psi on it. At idle with the controls in neutral the pressure that is seen on the gauge and the pressure at the dp sensor should be what the unloading valve is setting it at, since there should be no load sense acting on the dp sensor in neutral. The pressure in neutral is blocked by the main spools. The pressure then builds until it overcomes the spring in the unloading valve and returns to the tank. I have shimmed the unloading valve before with no increase in pressure. So either the pressure is getting by one of the main spools or the pump is not putting out enough flow to build the pressure required. I have had the pump apart though and the previous owner was not lying when he said the pump had been recently rebuilt. Any thoughts? Please let me know if I am understanding this all wrong.
I got a new main relief valve from the Hitachi dealer on the weekend and installed it. Nothing changed, ! I had talked to a few local people and they suggested changing the main relief. I just went through the main and circuit reliefs with all new o rings but I thought I would give a new relief a chance since they were telling me how touchy relief valves can be. Weird thing happened after I put all the valves back in, the thumb stopped working properly. It closes with some force but not like before and it can not open. I can see the cylinder rod move but it stops as soon as it feels the weight of the thumb. - checked the pilot pressure, 600 psi to top and bottom of the spool. - checked the spool, it moves freely. - took one line off the cylinder and tried to raise the thumb, a little oil came out and then nothing so its not bypassing the piston seals inside the cylinder. -pulled the circuit reliefs for the thumb back out and nothing seems to be stuck. Also the tracks are even slower to respond now. If I grab both levers and pull or push them all they way there is a 5 second delay before they start moving. They start slow and then pick up speed.
I'm curious, are the Dp sensor readings delayed now when you stroke the levers? If yes, does the angle sensor readings respond immediately?
I'm curious too! The diagnostic connector has been giving me trouble lately. It was connecting with Dr.Zx intermittently and now it won't connect at all. When I probe the 4 pin connector I seem to be missing one of the 5V signals. Lock tab up I get: top left 0.20V top right 0.13V bottom left 0.13V bottom right 5.13V The top left should be 5V also. The last time I had this issue I lost both 5V signals and that was due to the new china dp sensor being internally shorted and stealing the 5V signal. Putting the old dp sensor in brought back the 5V signals and communication. Unplugging the dp sensor this time did not help. Wiggling the harness does not help. All 4 pins go directly back to the pvc. I tested their continuity last time and all the wires were good. I don't know if this china pvc is failing or not. I have not even dug a hole with this machine yet. I tried poking around the other sensors looking for some sort of short but did not find anything conclusive.
Yep, those dash 2 and 3 machines have always been full of gremlins .
If only I knew that before buying, but I probably would have said "how hard could it be". I feel like that is the only way to get things done, if you don't try you will never get anything done! Ok, so today I put my gauge on the output of the pilot pump, and then checked the operational performance test section of the manual. For pilot primary pressure the spec is 52 +10 -0 kg/cm2. That works out to a range of 740-880 psi. The performance tests are supposed to be done in "P" or power mode. idle: 640 psi P mode: 690 psi I then added a 2mm thick washer to the stack of shims that were already in the pilot pressure regulator. idle: 720 psi P mode: 790 psi I decided to leave it there. Elsewhere in the manual I have seen a spec of 711 psi being called for. The next section in the performance tests that caught my attention was called "Main Pump Delivery Pressure" (in neutral) The spec is 31 +10 -3 kg/cm2 which works out to 440 + 140 - 40 psi, giving a range of 400-580 psi. Using the same gauge that I just measured the pilot pressure with, I hooked it up to the output on the pump. idle: 0 psi P mode: 0 psi The needle did not even move on the gauge! Do springs like the one in the unloading valve wear out and loose tension? Causing it to open early and bleed off pressure too soon. Since Dr.Zx is not working right now I back probed the differential pressure and angle sensors. idle: DP 2.92V P mode: DP 2.73V (higher voltage means bigger difference in pressure) I was expecting the voltage to go up when going from idle to P mode. In neutral there is supposed to be no load sense on the dp sensor. Only the pump pressure being regulated by the unloading valve should be acting on the dp. idle: A 3.14V P mode: A 3.64V (higher voltage means more pump angle) The bucket, boom, arm, and swing controls seem to respond fairly quickly (but I don't know what normal is lol). The tracks on the other hand... I can pull the levers and count to 5 while watching the pressure gauge. Then the needle starts to move and it takes another 3-4 seconds for it to reach almost 4000 psi in P mode. It only reaches the 4000 psi when using one track to turn and it stops moving.
So I was reading this thread HeavyEquipmentForums In there Knivens894 talked about an overheating issue that turned out to be the result of low pilot pressure caused by the spring in the pilot relief valve becoming weak due to heat. This made me wonder if my unloading valve spring could have become week. I took the unloading valve out today to have a look at it. The end of the spool where the spring goes looks like it has gotten hot or has been heat treated. You can see the blue color it has turned in the pictures. Why would the end of the spool need to be heat treated? Now I also tried to find out if the spring was actually weak by testing it. Here goes my maths lol! From the manual the unloading valve opens from a pressure of 284 psi I measured the bottom of the unloading valve spool and it comes out as 0.552 inches in diameter. Then apply the area of a circle formula (A=pie(r)2) lol and arrive at an area for the oil to push on the bottom of the spool of 0.239 inches So if it takes 284 psi to move the spool but the area for the pressure to work on is only ~ 0.25inches, that means that it should take 1136 lbs of force to compress the spring. Next I put the spring in my hydraulic press with a bathroom scale underneath it. When I got to the point where the spring was almost coil bound the reading on the scale was only 309 lbs. The oil pushes on the bottom of the spool after going through a tiny hole. I don't know if that would have an effect on my calculations. Any ideas?
I've only done a limited amount of work on old Hitachi excavators but can make some observations about what you show in the photo. My first thought is that it would take over 700 degrees to actually affect the temper of the spring. The spring in the photo appears to have the same amount of space between all the coils so I doubt very much that there is anything wrong there. The blue color is what I'm used to seeing on a component like this. I'm guessing that the spring fits over the raw end of the spool and the oil pressure acts against the machined end of the spool. I can also see the half moon groove in the middle land which tells me the spool is a regulating spool. I'm also wondering if there is a cap that is supposed to sit on the free end of the spring. Usually that cap with have a mark for an adjusting screw to seat into. I don't see any smoking gun to say something is wrong there.
Hi John, here is a picture of the rest of it... There is no adjusting screw on the top. This entire control valve is from a 120-3 even though my machine is a 120-2. The parts guy at my local Hitachi dealer told me that this is most likely a gray market machine and when they arrive in containers the guys just put them together with the parts that are in there, not necessarily the specific ones that belong to each individual machine. On the 120-3s the regulator was replaced with the plug that you see here. The relief on the bottom of the control valve became the new system relief. Some interesting results this evening. I decided the only way to rule out the spring for sure was to eliminate it as a factor. I cut a piece of pipe to the same length as the spring and installed it in the springs place. I figured it could not hurt the machine since when someone is operating the controls load sense oil is supposed to fill the cavity where the spring is and help hold the unload valve down in the closed position. Then the main relief valve comes into play and is supposed to open at 5000 psi. The "Main Pump Delivery Pressure" (in neutral) (in P mode) is supposed to be 400-580 psi. Previously I stated that the needle on my gauge did not even move. Turns out there is a marking for 100 psi literally right on the needle stop so there might have been some pressure but nothing significant at idle or in P mode. This time with the pipe in place of the spring there was still nothing significant at idle but when put into P mode I got 250 psi. Nowhere near the 400-580 psi that I was looking for but its something. Not sure if that means the spring is bad or not, but I'm leaning towards its fine. I can still hear a hissing at idle even with the pipe in place which tells me that some valve is still bleeding off pressure. Right? Another weird thing, I tried to use the thumb which has not been working properly since I refreshed all the circuit relief valves. I pushed the rocker switch to close the thumb and about 3800 psi was built, but when I went to open the thumb it did not move and no pressure was built. Only when I let off the rocker switch was there a momentary spike in pressure to about 4000 psi. I know the pressure is high for a thumb but I still have all the reliefs cranked. I am waiting to find the actual problem before trying to set them properly. Thoughts?
The only thing I can remember on a similar situation and I can't remember the model of machine was where the bore for the servo piston inside the pump was worn and there was enough leakage in that bore that the pump would not reach full system pressure. I don't remember how I figured that out but you might try to find out where that hissing noise is coming from. No way to know when you machine came into the country but back in the nineties when the big rush was on, the bulk of those machines came in whole and not in containers. I used to see rows and rows of them on the docks waiting for trucks to pick them up to deliver to washing stations or to leave the Ports in Seattle and Tacoma.
Hey John, that sounds like it would be tricky to figure out. The pump on my machine was rebuilt about 40 hours of use before I bought it. I have had it apart because I did not totally believe them, turns out they weren't lying and the pump is all new. That includes the head on the pump where the servo piston lives. Is there a good way to figure out where the hissing is coming from? Tips or tricks? Just by listening I can tell it is coming from the main control valve but it is very difficult to pinpoint. I can hear it the best when the machine is idling but if I rev it up it becomes almost impossible. I have tried a mechanics stethoscope with no luck, the cast iron of the main control valve is just too thick. Would a thermal imaging camera/gun work? They have gotten a lot cheaper lately. I was thinking of just letting it run at idle with the hissing going on and then start looking for a warm spot on the main control valve. Where the oil is blowing by it should be warmer? Should there be no hissing if it is all working properly? I have put in a new main relief from Hitachi but there are also 8 more circuit reliefs. Two for each of the bucket, boom, arm, and thumb. I don't want to replace them all if I don't have to. I am trying hard not to be one of those throw parts at it mechanics lol! That would have been quite a sight to see on the docks. Were any of the 120s ever not considered gray market?
That machine was done in 1996 as I recall. It was a warranty claim on a used machine that had less than a month of work when problems started. What I seem to recall was that the machine just wouldn’t perform. All the pressures were OK. I haven’t had much luck with stethoscopes either. I would be interested in listening to someone who has experienced success with an infrared camera. Most of the time I have had to use some twisted thought process to make a theory and then prove or disprove it. I’ll try some thoughts. If your system is load sensing, then the main relief shouldn’t be opening at all. The pumps will de-stroke before the pressure gets that high. The circuit reliefs can be a mixed bag. Some machines have them set low to release before the mains. Others are set higher than the mains. Their purpose is to release pressure shocks from outside the machine hydraulics. Say a tree limb falls across the boom or a big rock off a high bank crashes down. The exception to that is the thumb. The cylinders for that were never intended for machine system pressure. My gut kind of says something on the main valve is stuck or hooked up wrong. Does the hiss go away when you use something?
The manuals only help so much, the twisted thought processes are what really fixes a machine lol! Today I went back to the problem with the thumb. It would close but not open. It started after I had all the relief valves out and apart for cleaning and re-oringing. I didn't think it could be the relief since I had just looked at them and everything was good. So I checked that the spool moved freely, checked the pilot pressure and checked for internal leakage on the hydraulic cylinder. Everything was fine! It had to be the relief valve so today I swapped it with the arm relief beside it. Wouldn't you know it, the thumb would now open like before. The arm also turned into a bit of a pendulum so I know something is wrong with that relief because the problem followed it. I will have to check if the hiss goes away when I use a function, I was just happy that the thumb moved again today. According to the relief valve setting procedure I got from mg2361 the main relief is set to 5000 psi and the circuits are set to 5250 psi. Before I tried setting the the pressures I noticed that the thumb reliefs were backed off a lot more than the others. This makes sense since it would be nice for the bucket to be able to overcome the thumb while holding something, like a log. That way you could curl the bucket without having to try and match the speed of the bucket with the thumb and still hang onto the log. The bucket would just push through the thumb relief. I am a little confused though. I can't seem to find it right now but mg2361 sent me some info a while back. The info was from john deere and it mentioned that if any of the circuit reliefs were set to a lower pressure than the main relief, that circuit relief would turn into a main relief. Thumbs are usually set quite a bit lower than the main relief. It seems to contradict the info from john deere??? I am starting to think I have multiple questionable relief valves in the main control valve.
They will only turn into the main relief when that function is activated (if they are set lower than the system relief). With the spool for that function in neutral, the relief for that function is out of the equation. The thumb circuit relief is lower because the thumb cylinder must collapse with the bucket cylinder or you will be bending rods.
When I was installing thumbs, I would set them at 2,100 PSI. Swapping reliefs doesn't explain why the thumb would not move.
So I listened more closely today. The hissing is there at idle (in neutral) and is still there as I raise the rpm. I checked the thumb operation and it is working in both directions. I then lifted the boom off the ground and tried to move the arm. I can move the arm out away from the cab like normal. I brought the arm back to a vertical position and then tried to move it towards the cab. It moved about 2 feet towards the cab slowly and then world move no further. I had the control lever pulled all the way back. There was a pronounced hissing coming from the control valve. When I let go of the control lever the arm would swing back to the vertical position instead of holding the position that I had left it in. This is exactly how the thumb was behaving before I swapped the reliefs. The problem definitely followed the the relief to its new position in the arm circuit. Its really strange, that relief must have something wrong with it's poppet or spring because when I have pulled it out it looked closed and I could move the little pistons with a pick tool and they would spring shut. Once it is installed in circuit it is opening for some reason. Just to clarify this in my head... If I were to have the thumb set at 2100 psi like John C suggests. When I go to use the thumb will the thumb reliefs turn into a main relief because 2100 psi is so much lower than 5000 psi? If I were using another function at the same time would it be limited to the 2100 psi the thumb is set at? I feel like the thumb pressure setting should have no effect on the other functions because that would not be very productive. I attached some pictures of the control valve from the manual. Can you guys make better sense of it than me? It looks like the variable pressure compensators might be involved in this low pressure mess. There is another problem where if I move the boom and arm together slowly its fine but if I pull on both control levers fully, the arm will move first while the boom remains stationary and then the boom will move once the arm is done moving.
The compensators appear to be in the motor circuits and not the cylinder circuits. Is there anyway that the spools got put in the wrong holes? The circuit relief is always a circuit relief. The main relief is installed between the pump and the main control valve. The circuit relief is installed between the main control valve and the function that is being operated.
Compensators are in every circuit. Don't get hung up on this. Thumb circuits have to be set to 2500 psi or less to protect the thumb cylinder and will not affect the rest of the machine. You obviously have an issue with the relief you swapped, so fix that.
Thanks for the replies gentlemen, I have been sick the last couple of days but feeling better now so I will pull that relief soon to check it out.
Ok, got the problem relief valve out and there is a little carnage lol! I remember now that when I had all the reliefs out to service them there was one that sounded a little funny when I was screwing it back together. Turns out that funny noise was the spring perch on the poppet crumbling to bits and the poppet getting pushed down into the spring itself. None of the others made any funny noises while going back together. Thumbs are not installed from the factory so the relief locations for the auxiliary spool are just plugged normally. When someone installed this thumb they would have had to buy relief valves for it. I wish I knew what kind they were so I could know if this was a oem relief or a aftermarket one that failed. Guess I will never know. All of the relief valves are turned all the way up right now except for the new main relief that I got from Hitachi. That I left because it was supposed to come pre set. I was planning on waiting until the real cause of the low pressure was found and then I could back them down to their proper settings. I turned them up all the way because I didnlt know if one of them had a weak spring or what was going on. Probably should have just stopped turning after one full turn made no difference to any of them. Live and learn
Ok, I have my old main relief valve taking the place of the broken one right now and the machine is back to being as broken as it was before thumb stopped working. I will probably swap over the poppet and seat from the old main relief into the thumb relief that failed. I can't leave the old main relief in the machine because it does not have the anti-cavitation feature that the circuit reliefs are supposed to have. Yesterday I received the thermal imaging camera that I ordered. It is a Hikmicro B10. I decided that my first test would be to start the excavator and just let it run with all the controls in neutral. I know that there is a low pressure problem in neutral so might as well start there. The pilot system warmed up first which was expected but then after about 10 minutes I noticed something funny with the travel pressure hoses that run to the center joint. One of them was warmer than the others. With all the controls in neutral they should have all been the same temperature since no hydraulic oil should be flowing. The hose that is getting warm is coming from the bottom of the right hand travel spool. Could this be the internal leak that is causing the low pressure? Here are some thermal pics of the center joint.
Is there a method/procedure for figuring out if the main control valve itself is worn? When I had the control valve out I was able to polish out the small vertical scratches in the spools with wet sandpaper dipped in hydraulic oil. I did not do anything to the bores that the spools ride in though.
Hey Max, thanks for the link but I already have the manuals for this machine, both in PDF and hardcopy. What I really need is info on how much is too much when it comes to wear in the main control valve. I have been reading that a lot of hydraulic systems are designed with 3-8 um (0.00012-0.00031 inch) of clearance between the spool and the bore that it rides in. Seems like once its a little scratched it would be all over in terms of internal leakage. Does anyone have experience with salvaging control valves? What can and can't be done or when it's too late and time for a new one.
I don't understand what you are trying to get at here. I have the procedure for setting the circuit relief pressures from mg2361. My workshop manual only has tightening torques and the painting scheme in the general information section.
Hey John you said this earlier in the thread... I have been looking back at some of my pictures from when the main control valve was apart and comparing them to the parts diagrams I can find online. This first pic is of the boom, arm and thumb spools. The bucket spool was still in the control valve, so not in the picture unfortunately. From what I remember it looked like the thumb spool though. This next picture is from a parts diagram. To me something looks off. In the diagram the thumb and the arm look the same, the boom is a little different and the bucket is the most different. What do you guys think? mg2361 do you have a clearer diagram that I could compare my spools to?
Unfortunately, no. But what I do have is that the spools have a number stamped on one end. I have what spool number goes to what port. Propel spool (left or right) - 32 Swing - 37 Bucket - 24 Boom - 4 or 04 Arm - 25 Auxiliary - 6 or 06
Awesome, thanks! I will pull the spools and have a look.
So... the plot thickens! I pulled the spools today and had a look. Only one spool had numbers that matched the list. Supposed to be | What I have Propel spool (left or right) - 32 | 30 Swing - 37 | ? (scribed on 9) Bucket - 24 | 26 Boom - 4 or 04 | 27 Arm - 25 | 28 Auxiliary - 6 or 06 | 06 Here are some pics.
This is a pic of the tag on the main control valve. Maybe someone can tell me if this control valve even belongs to this machine?
UH-OH! I don't have any listing for anything other than the EX120-2/3. Maybe my list is obsolete?
I love these problems... not! I feel like I always get the ones that nobody else has ever had. I was really hoping the numbers on the spools would be correct but just in the wrong order. With all the numbers except for the thumb being different I decided to google the numbers on that tag. When I put in the last number (4304717) I get results for a ex100-2 or ex100-3 main control valve, not a 120-2/3. They must be really similar if not the same because all the hoses and pipes bolt up. Is there a way I should go about manually verifying which spool should be in which hole? Try to measure the distance from the bottom of the spring seat to the internal openings in the control valve to see if the lobes on the spools line up?
Ok I have not tried measuring the spools yet but I wanted to run another theory by you guys. I was picking up some bucket ears for a digging bucket I am modifying from the local water jet guy and he had some ideas about my track problems. I can move foreword and back but when I try to turn with one track or the other it will do about an 1/8 of a circle and then just stop. Maxes out at about 4000 psi in p mode but does not move. He thought it might be that my center joint is leaking internally. Does this sound reasonable? The center joint is dry on the outside. Earlier when I posted the thermal pics of the center joint, one of the right hand travel motor hoses was warmer than the others while idling. When looking from underneath that hose is still warm but the case drain from the left travel motor was warmer weird ?!
Internal leakage of the rotary manifold is a possibility. Usually when they leak internally, you also have a mis-track.
Hmmm, I don't seem to have a mis-track issue but the seal kits are not very expensive so it might be worth doing. I read on a final drive site that if you run a case drain test on both motors and they are with in spec then the rotary manifold could be the next suspect. The kit looks like it has lots of seals, so plenty of room for weird problems to occur.
Does your machine have two speed travel? I've seen plenty of times the range was stuck in high range and of course the machine wouldn't turn but it traveled straight.
It actually has 3 speeds. Turtle, slow and fast. I think turtle is supposed to be 60% of slow. A while back I tried pushing the speed buttons while tracking. I held the track leavers in the same spot and pushed the buttons. It seemed to pick up and slow down depending which button I pressed. So I think speed control is working but the differences in speed between the modes seemed too small. I feel like I had to concentrate a little too hard to notice the difference.
Three speed units that I have worked on use the pump outputs to change one range. Say low to mid is the pump output and too high done using the range selection in the motors. The high range is done usually by using pilot oil controlled by a solenoid to change the tilt angle of the swash plate in the motor to minimum stroke. Minimum stroke means faster rotation of the motor but less torque. Typical issue is either the solenoid and signal from the computer or leakage between the range signal in the swivel into the drain port. I've also seen leakage in the servo piston for the swash plate in the motor cause the issue but that usually only affects one motor at at time.
Thanks John, I believe you are correct with the function of the 3 speed control. Sounds like this swivel joint can cause all kinds of issues. I think I am going to have to order a rebuild kit.
Well, I received the seal kit for the swivel joint and proceeded to install it. When I opened it up it looked like someone had already been in there. The seals were not too bad. I put the new ones in anyway and its all back together now. The problem with not being able to turn is still there. I am going to check the travel speed time to see if it is stuck in high range. There is a spec in the manual for how much time it should take to cover 20m. Fast 13sec + or - 1sec Medium 21sec + or - 1 sec Slow 34.5sec + or - 2sec I am also now looking into the proportional solenoids. I have noticed that when I boom up and arm in at the same time the boom won't move until the arm is finished. Also while tracking I cannot boom up, only boom down.
Just finished doing the travel speed test. I tested each speed twice. Fast: 23, 24 seconds Medium: 27, 28 seconds Slow: 31, 31 seconds Looks like there is a difference in the speeds but it is not nearly what it should be. Only the slow speed is close to what it should be. Also in slow speed it takes a couple of seconds for the tracks to start moving after the levers have been pulled. In medium and fast the tracks start moving right away. At the end of the test I ran a couple more passes with the travel proportional solenoid unplugged, it made no difference to the times. Mistrack is supposed to be measured over the 20m distance also. After running 8 passes I would say the machine ended up about 3/4 of a track width over from where it started. I going to call it good. The actual spec is no more than 230mm off course in one pass. Any ideas on what these times indicate?
I just finished testing the Pi Pressure. The results are interesting! Spec is 512 psi + or - 7 psi I got 690-700 psi. The needle fluctuated a little. Test is supposed to be done in P mode (full throttle). It showed 690-700 psi through the whole throttle range from idle to P. The pilot pressure is set at: 720 psi idle, 780 psi P mode. Looks like pressure reducing valve is reducing the pressure and holds it steady through the rpm range but, it is clearly not reducing the pressure enough! This Pi Pressure is put on one side of the variable pressure compensated valves. The proportional solenoids then act on the other side. Since my pressure is too high the proportional solenoids can't do their job properly which I think explains my travel speed and combined operation issues. Now to figure out how to bring the pressure down! Might have to get a new reducing valve.
Ok, I pulled the pressure reducing valve apart today (controls Pi pressure) and removed the shims. 1 0.5mm shim and 2 0.2mm shims. Put it back together and got 350 psi. Then put the two small shims back in, no change, put the big shim in and no change, still 350 psi. I then added a 1.75mm washer to the stack and got bang on 500 psi. I am thinking that a few months back when I was putting new orings into everything I could think of the pressure reducing valve must have gone back together with the spring not being properly seated. It makes more sense that I would have to shim it to increase pressure because I had to with the pilot pressure regulator and things usually loose pressure over time not gain it! Now to the travel speed. I tested the travel change over pressure and got 400 psi. According to the specs I should be getting full pilot pressure there, which in my case is 720-780 depending on the rpm. I know the travel speed solenoid is working because I got the 3 different times to cover 20m posted above. Maybe the little spool is sticking that the travel speed proportional solenoid acts on. I am pretty sure its fine though because I have had all the proportional solenoids off to put new orings on the sleeves that the spools ride in. The proportional solenoid itself is a new one so I gave the adjustment one full turn in but the pressure did not change. Any ideas? Here is a section from the trouble shooting. I added some notes in red.
More weird things found with the thermal camera today! My brother was watching the main control valve while I pulled one of the track levers. The throttle was in L, I pulled one track lever and had to wait a couple of seconds for the track to try and turn. It tried and then did not move. The engine did load up so it was trying. I held the lever there with the track not moving and the engine loaded. While watching the mcv the hard lines for the bucket and arm variable pressure compensators started to warm up. On the camera you could watch them become more and more yellow while the track lever was held and the track was not moving. After letting the track lever go the lines could be observed cooling down. We waited until they reached the same temperature as the other hard lines which did not take very long. Then we did it again, held the track lever, track stalled, and the lines for the bucket and arm vpcv warmed up. The bucket was off the ground and the control joysticks were neutral, only the one track lever was being moved. I don't know why compensation for the bucket and the arm would be required? Maybe I should try unplugging the two proportional solenoids that feed those lines?
I unplugged the proportional solenoids for the bucket and arm, and then held the track lever and it stalled just like yesterday. While holding the track lever and watching those two hard lines with the thermal camera I could see them heating up just like before. So unplugging the solenoids apparently did nothing, there is still oil flowing to those variable pressure compensators even though they should not be active when only the track function is being activated. Guess I am going to have to pull that little solenoid bank apart and have a little looksee! Does anybody have a diagram or somethings that shows how the pilot oil is supposed to flow through this solenoid bank? This is what I'm talking about:
Did a little more testing today. I was looing around with the thermal camera and noticed the swing parking solenoid was warmer than the other solenoids at idle. According to the manual the swing parking solenoid should only activate when the swing pressure switch or arm in pressure switch is tripped. Then the solenoid sends full pilot pressure to the swing parking brake, pushing on the spring and releasing the brake so the machine can swing. This means the swing parking brake is normally "on" without pressure from the solenoid, so the solenoid should have been off while the machine was idling with no functions being used. I then unplugged the harness connector to see of the swing parking brake would apply. Turned the machine on and tried to swing and wouldn't you know it, it swung just fine. So even with the solenoid unplugged pilot pressure must still be getting to the swing parking brake. I teed in a gauge between the solenoid and the swing motor and got about 690 psi. Pilot pressure is 720 psi at idle. So I have almost full pilot pressure leaking from the solenoid bank to the swing parking brake with the solenoid unplugged. Next I noticed the line for the travel speed control was getting warm while the machine was still stationary and the travel speed was set to turtle mode. The travel speed solenoid is only supposed to send pilot pressure to the travel motors when fast speed is activated. With slow and medium the pressure in the travel speed line should only be 14-71 psi. I put my gauge back into the travel speed line and got 200 psi. I then unplugged the solenoid and got 150 psi. Previously while engaging fast travel speed I had recorded only 500 psi when it should have been 700+ psi. Maybe I can't get the full 700+ psi when it tries to shift to fast mode because it seems to be leaking pilot pressure even with the solenoid unplugged. I also read in the manual that it only takes 183 psi to start the change to fast travel speed. This could be the cause of my week travel issues. Even in turtle mode there is pressure leaking into the travel speed changing line and possibly partially shifting the motors into fast travel mode. I need to get a more accurate gauge for these lower pressures. My lowest gauge goes from 0-3500 psi but the needle rest is the 100 psi line so its kinda hard to tell. I will have to find a 0-1000 psi gauge.
Alright, I had the solenoid block apart and the manual was not very clear on the swing parking operation. In the previous post I described it backwards. Turns out the swing parking solenoid works in reverse compared to the rest of the solenoids, which are for proportional control. The swing parking is simply on/off. In its resting state the swing parking solenoid allows oil to flow while the proportional solenoids in their resting state do not allow oil to flow. This is why the swing parking solenoid is "on" while the machine is idling. It is blocking the oil flow so that the parking brake is engaged. When you want to swing the machine the computer turns off the solenoid and oil flows to the swing parking brake and releases it. I think they designed it like this so that the solenoid would not have to be "on" the whole time the machine is in operation. After pulling all the parts out I noticed some were missing according to the parts diagram. A small spacer disk and spring washer. The spacer disk was missing from the travel speed control solenoid. I made new one and I don't think there is anymore pressure leaking out causing it to change travel speed without any buttons being pushed. I put compressed air into one of the pressure ports and activated each solenoid individually with a battery. Air would flow only when the solenoid was activated so I believe they are working fine now. Still waiting on my 0-1000 psi pressure gauge so I can know for sure.
Doing some more testing while waiting for my pressure gauge. I believe the leaking solenoids are fixed so it is now longer trying to change into high speed travel without my say so. Problem is the tracks are sometime really slow to respond to input. When I first fire it up I can move the travel control levers and it responds basically right away. If I try to do some digging and swinging and then go to move the tracks I sometime have to wait for 10, 15, or 20 seconds for a response. I hooked a gauge to the pilot cap and there is pressure there right when I pull the lever. The pressure doesn't drop while I'm waiting. Eventually the sound of the engine changes and the tracks pick up speed slowly. Like it finally realized there is load on the system and a response from the pump is required. I have tried moving another function while waiting and it sometimes causes the tracks to start moving but not all the time. I know this sounds like a load sense issue with the shuttle valves but I did clean those when the mcv was out. They weren't dirty then so I kinda doubt they are now. It also still has: - low system pressure when everything is in neutral - combined operation for boom and arm does not work - while tracking the boom will not raise at all. - swing is really weak - arm out is really weak - tracking is better since its not going into high speed anymore but response can be delayed and when turning it will sometimes just stop like a got too difficult for it. I am waiting for the gauge and a new palm pilot to put drzx on. The one I have seems to connect 1% of the time lol!
When you get your palm pilot, it will be interesting to see how fast the Dp sensor is reacting.
Yes, it will! The weird thing is that all the other functions seem to respond right away. I am still a little suspicious of the Dp sensor though. Have you ever heard of main control valves developing cracks internally? I had somebody suggest this to me as a possible cause for the low pressure when everything is in neutral. The other thing they suggested doing is capping every line that leaves the mcv and then opening one circuit at a time to see if fluid is leaking into the circuit.
Absolutely. Just haven't seen it in a Hitachi control valve....yet.
Hmmm, well I just might be your lucky customer lol! Is there a way to diagnose an internally cracked mcv? I wish I knew what to look for when I had it out before!
I've seen in Dash 3 Komatsu excavators. The only way I've found them is because pressures were lost when they shouldn't have been or something else moved when it should have. One machine had split in between the valve halves. Two machines had a break in the straight travel valve circuit. We were never sure of what happened, only that the problem went away when we changed the problem half of the valve.
I suppose all the high pressures within the mcv will eventually find the weak spot in a casting if there is one, excessive heat probably doesn't help either. I am going to run more tests when I get my gauge and palm pilot but I will keep this scenario in mind. Does anyone know of good places to get used main control valves? I would assume the dealer doesn't have any or would be way too expensive. Just want to check into all my options.
I talked to a guy at Flemming's Equipment Services the other day. They sell used Hitachi and Deere parts and are fairly close to me. I asked if they had any main control valves for my machine because I have a hunch there might be an internal crack. His reply was interesting... he said he did not have any in stock but that the ex120 main control valves were known for cracking. In didn't tell him about any of the issues I am having and asked if he could explain a little more.... he said they were known for cracking through the travel ports and that they would then cause all kinds of weird travel issues. I couldn't believe my eyes when I read that email, maybe this is finally the solution! I am going to contact the Hitachi dealer but I am expecting big money or not available. I am kinda leery of used ones as well because what if they already have a crack or are about to crack. Has anyone ever heard of fixing internal cracks in main control valves? Maybe by sleeving the affected bore? If one could find the crack/cracks with a bore scope maybe something could be done by a machine shop? These are some part numbers I have found if somebody knows where a good used mcv can be found: ex120-2 4254646 ex120-3 4338612 ex100-2 4254645 ex100-3 4339736 and the one that is actually on my mcv 4304717
Very interesting! We had a very small population of those machines (Deere anyway) in our area, so I have not heard that. That is what I love about HEF, learn something new every day.
Time to share preliminary results. The main control valve is back out of the machine. I have not found the crack yet but I did rig up a test with compressed air. I made an adapter so I could hook an air line to the inlet port where the pump feeds the mcv. Oil flow is supposed to be blocked by all the main spools. The unload valve opens after 283 psi and relieves pressure back to the tank. I am only putting in 100 psi shop air so the entire mcv should have acted like a pressure vessel, with maybe some minimal leakage. When the air was introduced it started coming out of all the returns and some of the travel ports surprise, surprise! Since the unload valve should not be opening at this pressure there must be an alternate route from the pressure side to the return side. I then plugged the return ports and pressurized the mcv again. The air was defiantly coming out of all the travel ports, some more than others. I felt for it by hand and there was no air coming out of the other circuits just the travel ports. Looks like this confirms what the thermal camera found with the travel hoses heating up at idle with the controls in neutral. Here are some pics and a video. Hopefully I can get the video to work.
Lets see if this works...
Ok ladies and gentlemen, I tracked down a "new to me" main control valve. Got it delivered, replaced a bunch of orings, painted it and now installed it. I have not run any real tests yet but its looking promising! I used to be able to hear a hissing sound coming from the main control valve while the machine was idling. It would fluctuate up and down, kinda intermittent but always there. Now there is no hissing, its pretty much silent in the control valve area. I am guessing that the hissing was oil bypassing through the internal crack. The new control valve also had air leaking out the travel ports but not nearly as much. I think the air coming out the travel ports is because those ports are the only ones that are connected to the return circuit while the spools are in neutral. They don't receive pressure in neutral but they are open to return so that pressure does not build in the lines causing the parking brake to release. I got a gauge and mounted it to the end of the air line I was using to pressure test the control valves. I could then compare the pressure at the control valve to the pressure at the regulator from the compressor. When the two numbers are divided I can get a percentage of leakage. Cracked control valve: 32% loss "New" control valve: 20% loss "New" control valve after orings: 18% loss That was a relief to see that the new one was better in some quantifiable way. I have tried the tracks and they seems to be acting consistently. It doesn't just randomly stop anymore. I also climbed a hill on my driveway which I am pretty sure would not have been possible before. There is more testing to do and probably some tweaking of things that I calibrated while the broken control valve was in there. Here are some pics... Had it delivered to my work so I just backed my truck up to his power tailgate and slid the pallet in. The packaging left something to be desired.
Got it in the shop and started to strip it down.
I have not seen the DP sensor before. Anybody else seen this type? It seems to be non-adjustable. Type. KH22 No. 370069 Range. 0-2.55 Mpa Nagano Keikico Made in Japan
Gotta remember to split the control valve in half and get those orings on the inside.
Fully painted and ready to install.
The new Dp sensors from Deere sub to a non-adjustable sensor.
Just wanted to say that 22 years ago I worked for a mining company in Northern Ontario that had a lot of Hydraulic Drills that after a few years every single hammer body developed cracks that would only leak when the drill was in percussion mode. With way too much testing we always found out that, with even sleeved bores the leaks would come back. It was a simple fix. New housing, valves and pistons and all was good. We had figured it out with dye on a test bench. The leaking oil had the dye in it. We even had air drills that leaked between ports from the percussion hammering also. It would not surprise me at all that a housing could crack. Maybe the unit worked on a hammer before you owned it or was made weak in one location at the factory. The possibility is always there. Simon C
If that's the case then it looks like someone replaced it at some point with a genuine part. I like that! Very interesting Simon, before I went through all this I would never have thought that a big lump of cast iron could have these issues. I knew that lots of heating and cooling could affect cast iron, like trying to weld it with the wrong technique. It makes sense that vibrations and shock loading from a hammer drill would do some damage, however I am leaning towards the factory defect theory. When that one wrecker told me that they were "known" to crack that got my attention. When a guy who sells parts for a living knows about a problem, it must be fairly common. Did a little test today. I checked the pump pressure with controls in neutral. Spec in the book is 440 - 580 psi (P mode) Old control valve: Idle 260 psi P mode 270 psi falling to 240 psi New control valve: Some strange things happened, I might have to re-test, something might be up with my gauge. After un hooking the gauge the needle remained at 380 psi. I am pretty sure it normally falls back to zero. Idle (cold) 280-300 psi Idle (20deg C oil temp) 360-380 psi P mode 390 psi (stable) I know these numbers are lower than the book spec but in other parts of the manual I found this... The engine does idle better with the new control valve so the dp sensor must be getting the correct differential pressure to signal the pump to run at minimum output. With the old control valve the differential pressure would have been lower causing the computer to think that there was load on the system. It would then signal the pump to put out more flow which put an unexpected load on the engine while it was idling causing the engine to run rough.
I hope you get it all figured out. Sometimes there is no way around new parts. I use to live in West Kelowna but am back in Alberta. All the best to you in your repair. Simon C
Thanks Simon! You're so close yet so far away haha. Ok, I don't know how I would be able to measure the pressure at the pump and get the spec the book was calling for? According to the picture from the manual that I posted above, the unloading valve opens to control the system pressure in neutral to 284 psi. The initial readings with the gauge were 280-300 psi, so I am going to call that good and say that the unloading valve is working properly in this control valve. Now the gauge is a little wacky. 360 psi seems to be it's new zero point. I put the gauge back on the machine this evening and it read 640 psi. 640-360 is 280 psi so it seems to still be working but with a new zero point. I saw some people on YouTube talking about "venting" or "burping" a gauge. Basically pressure can build up inside fluid filled gauges from temperature or altitude changes causing the needle to move. If the little rubber cap on the top is cracked open a hair the needle should fall back to zero. I tried that and nothing changed, still stuck a 360 psi. Any ideas? I am going to have to look into this a little more.
Get a new gauge.
Caterpillar sells gauges that are pretty good. Even $50 for a gauge may sound like a lot but minimal as compared to a whole day wasted over a faulty gauge. I have quick connects on my gauges and 2 of each. Change gauge and if still same then move on with diagnosis. I don't like working a day for $50.00 Simon C
I am looking for a new gauge right now. The problem is that when I bought my testing kit the gauges in it came with a weird thread on them. You can see it in the first gauge pic. It called G1/4B, its a british pipe thread and it turns out that everything sold in north america is NPT. I didn't know this or else I would have got a different kit. The gauge that is broken I got from a seller on ebay in Australia because they seem to use that thread and I wanted a gauge that would work with the hoses and adapters in the kit. I have contacted the Wika gauges location in Edmonton because their site shows that they sell a adapter to go from 1/4 npt to g1/4b. Then I could get any npt gauge and run it with the other pieces in my kit. I will look into the CAT gauges.
Ok, got my new gauge and put it to the test. It's a zero to 1000 psi gauge so I can use it for all the lower pressures like pilot pressure and the system base pressure that I have been trying to measure. I got the 4 inch dial gauge because I thought it would be easier to accurately tell what the reading are. I am posting a video link so you guys can see a little better. The needle dips once in a while but it corresponds directly to the pulses I could feel in the pilot line. The pulses are from the pump angle control solenoids. I know that when the oil is warmer the solenoids fire a lot more often so the needle would probably stabilize. When the needle is not dipping it seems to show 280-290 psi and the book spec is 283 psi. Seems like this new control valve is OK. I have moved the machine around and the tracks have not randomly stalled on me either. I think the last issue now is that the proportional solenoids are not compensating properly so combined operation is not great. As you guys saw earlier I rebuilt the proportional solenoid block so I need to go back and check that the pilot pressure and pilot reduced pressure are correct. Then put a lamp harness in and see if the computer is actually firing the solenoids and possibly adjust them.
Great detailed reports and follow-up. A lot is way beyond me but some folks will be able to work with your write-up.
Thanks Gary, I have received quite a built of help from the forum members and I hope all this info can be helpful to somebody else. Small update: Since the the base system pressure seems to be good now that the new main control valve is installed, I wanted to test the upper end and see if the system relief pressure is correct. It does not matter which function I choose to test the system relief pressure with, the main relief valve will always open at it's set pressure. If I wanted to test the individual circuit relief valves I would have to temporarily raise the system relief valve pressure setting above the circuit relief valve setting to observe it. The circuit relief settings are 200-400 psi higher than the main relief on this machine. To test the main relief the hydraulic oil temp is supposed to be 50C +or- 5C. I was only able to get the oil to 20C. It was about -10C ambient temp when I did the test and I did not want to work the machine a bunch to get the oil temp up. The throttle should be in "P" mode (full throttle) and then I held the bucket in the dump position for a few seconds over relief and recorded what the gauge said. I got 4800 psi. The specs in the manual are a little funny: 350 (+20 -0) kg/cm2 or 4978 (+284 -0) psi then below this in the same row and column is says 370-300 kg/cm2 or 5262-4270 psi Later when the weather is nicer I will do more testing but for now it looks like buying and installing the new to me used main control valve was worth it. I also installed some leds to replace to burnt out factory sealed beam lights, they are crazy bright!
Its amazing what a control valve without micro cracks in it can do for proper functions. Glad it is mainly worked out. 4800 PSI is a lot of working force for any machine. It translates into digging force. Glad she is better. Simon C
Love the lights!! I put an LED light bar on the cab of my CAT 320CL and 2 LED "pod" lights on the back...they are wonderful.
Well, looks like we are not exactly out of the woods yet! In the previous post I mentioned getting 4800 psi, but that was with 20C hydraulic oil temp. Today it was 25C ambient and I was able to get the oil up to 50C like the manual wants without any trouble. Then I ran the machine up to full throttle (P mode) and stuck a pipe in the drive sprockets to test the tracks over relief. 4200-4400psi was the result. I held the bucket over relief in both the dump and curl positions and got the same thing, 4200-4400 psi. Next I gave the main relief valve a quarter turn clockwise, expecting a pressure increase but got the same 4200-4400 psi. Then turned it a quarter turn counter clockwise expecting a decrease in pressure but still got the same 4200-4400 psi. The spec that I mentioned above (5262-4270 psi) I figured out is the upper and lower limits of the working pressure. Looks like I am hovering around the lower limit... but I am confused as to why I didn't get any change with the main relief valve adjustments???
If I recall correctly, you do not have a surge relief, correct?
Hey mg2361, I'm happy your still checking up on me! My old control valve with the internal cracks was from a ex100-3, it had the plug on top and a surge relief that acted as the system relief on the bottom. The "new" control valve is correct for my machine, it being an ex120-2. There is a "System Pressure Regulator" on top (this is the one I was trying to adjust) and a "Surge Relief" on the bottom.
Maybe the surge relief is set too low??
Ok, I first gave the surge relief a 1/4 turn and then 1 full turn in. Both made no difference, still 4200-4400 psi. I started with a 1/4 turn because after doing the conversion 28.5 kgf/cm2 is equal to 405 psi. The system pressure regulator on top feels like it is at the end or just about the end of it's adjustment range, bottomed out. Seems to me someone was trying to adjust the pressure when this control valve was in a previous machine and just kept on turning until they got to the end. I was hoping to adjust the surge relief to where it needed to be today and then back off the system pressure regulator to just below it. I didn't want to keep turning adjustment screws for no reason so I just left the surge relief at 1 full turn in from where it was. The functions that I used to test the pressure today were boom up, stick out, bucket dump and bucket curl.
Please note that the system pressure regulator valve is integrated into the Unloading valve.
Thanks Lachau, I understand that system pressure regulator sits on top of the unloading valve and that they work together to control the system pressure. I am unsure of what you would like me to check, or what I might not be understanding? This is the procedure I have been using to check the system pressure.
The pressure of the system depends simultaneously on all 03 relief valves A_B_C as shown below. You must check; calibrate all three types of valves. You should check and calibrate 02 relief valves A & B at the same time first. If the pressure is still not reached, we will consider the relief valve C. As MG2361 mentioned above, it is possible that your surge relief valve has been set to a low value. You should try increasing the pressure value of surge relief valve B to see how.
Added for more clarity.
Alright, I tried increasing the system surge relief (B) valve first. I turned it in (tighter) a full 5 turns and it made no difference. I then tried adjusting the overload relief valve (C) for the thumb circuit. It was around 4000 psi and I wanted it lower, around 2400 psi. I backed it out in 1/4 turn increments and it reduced the pressure by about 400 psi (28.5 kgf/cm2) each time just like the chart says it should. This made me believe that there is something else going on. The system relief (A) was a 1/4 turn away from being bottomed out when I tried it. So someone else was obviously in there before me and 5 turns of the surge relief (B) did not make a difference. I decided the system relief (A) was faulty so I pulled it out and took it apart. The cone shaped poppet had been pressed so hard into it's seat that the metal had deformed a little. Instead of the cone having a crisp line around it from where it contacts the seat it was more of a band. Now since I already had it out I decided to simplify the system by putting in the 120-3 parts from my old control valve. That means I replaced the system relief (A) with a plug and I removed the surge relief (B) and installed a brand new from Hitachi surge relief. I had bought it when I was trying to figure out what was wrong with the old control valve. In the 120-3 setup the surge relief (B) turns into the main system relief. The new from Hitachi main relief has a red paint dot on the cap. I am assuming that means it has been tested and calibrated prior to me buying it? I have not tried to adjust it at all. So after eliminating the system relief (A) and installing the new main relief (B) I tried it again. Disappointment, I got the same 4200-4400 psi. I get that same pressure on multiple different circuits. I find it hard to believe that the circuit relief valves (C) could be the problem. What are the chances that I get 4200-4400 psi every time whether I try the track and swing which are external to the control valve or the other circuits like bucket ,boom and stick. It seems unlikely that the circuit reliefs in the control valve which came from a different machine match exactly the circuit reliefs on my machine (tracks and swing). I am almost thinking that the pump is not going to full stroke/angle (24 deg) either because of the pump angle sensor or the dp sensor. I checked the engine rpm in P mode and got 2365 rpm. The spec is 2350 + or - 50 rpm. What do you guys think? Please let me know if you see flaws in my logic.
Unloading spool and spring OK?
finally, my guess is that your pump has degraded! The pistons + cylinders of the pump are worn and loose! You try a method that is not in the book, not the official way. fabricate a gasket to limit the minimum angle of the pump. As you restrict the pump's minimum angle which means you increase flow in relief mode, it can help increase system pressure.
Yes, I believe the unloading valve is working fine. Interesting solution Lachau! I am willing to try it but I have some questions first. - If I were to add a shim to the spring on the unloading valve would that raise the pressure? - The DP sensor in the control valve is the non-adjustable type. I have an adjustable DP sensor in my old control valve that I think I adjusted to 1.1V per Lachau's recommendation. Would installing it cause the PVC command more pump angle and raise the pressure? - The pump was rebuilt about 50 hours of use prior to me buying the machine. I have had it apart and everything looks brand new inside. I did not measure any of the pistons or bores because I couldn't find any specs to reference. Is it possible that the new pump parts are not very good quality and the tolerances are too loose causing it to not flow enough oil to build the right amount of pressure? Or do new pumps need to be "broken in" so that the parts mate together better and then more pressure will be developed? When I had the pump apart I got a local hydraulic shop to "lap" the bronze face of the lens plate to the barrel. He did it on his lathe. The picture is before he did the lapping. It's smoother now.
1/- "- If I were to add a shim to the spring on the unloading valve would that raise the pressure?" The answer is "Well, maybe it could be". 2/- "- The DP sensor in the control valve is the non-adjustable type. I have an adjustable DP sensor in my old control valve that I think I adjusted to 1.1V per Lachau's recommendation. Would installing it cause the PVC to command more pump angle and raise the pressure?" The answer is "Well, maybe it could be". 3/- Have you tried adjusting the angle sensor? Adjusting the sensor angle can also increase system performance a bit.
I set the angle sensor according to the instructions in the manual. It says to set the angle sensor to read 4.40V +- 0.03V when the pump is at 24 deg. - Is there a different voltage that you have found to work better? I tried a quick test today. I unplugged the pump angle control solenoids and let the pump angle fall to maximum (24 deg). I then put the machine in P mode and held the bucket dump over relief. The pressure easily got to 5200 psi and the engine was about to stall so I let off. If I had held it there I'm sure the engine would have stalled. Looks like the pump is plenty strong enough. I was thinking of loosening the bolts on the angle sensor so I could adjust it while a function is over relief and in P mode. Then I could watch the pressure gauge and stop when I get 5000 psi. - Is this a bad idea?
ALRIGHT. Just like that, move forward
We have success! I can now reach 5000 psi with every function in P mode and the hydraulic oil up to temperature (50C). I unplugged the pump control solenoids and let it fall to maximum angle (24 deg). I then back probed the electrical connector for the angle sensor (one probe on signal and the other on ground) and got a reading of 4.48V which is actually a little high compared to the spec of 4.40 +- 0.03V. Next I loosened the bolts on the angle sensor and rotated it until I got a reading of 4.0V. I might have been able to get away with adjusting it to 4.2V or 4.3V but I didn't bother trying. The amount of movement it takes to make a change in the voltage output is very very small, so be careful. Right now its making the pressure it is supposed to and I'm happy. If I end up changing it for some reason I will let you guys know. This also confirms that the new from Hitachi relief valve was preset from the factory. I did not have to adjust it.
congrats on your success.
Great job Jason! It is fascinating how little a change in the angle sensor adjustment can make such a big difference in performance. We have many Deere solutions (bulletins to those who don't speak Deere) on angle sensor adjustments and how they affect performance.
Amazing work Jason! I have the same machine (John Deere 490e is the Hitachia 120-2/3 body with a JD engine). It sounds like you are pretty advanced in your knowledge on this machine, I posted a newbie question on a weak boom function issue, perhaps you may have some tips? HeavyEquipmentForums
hi - why did you blow into the distributor? I have an ex120-3 m, and it seems to me that I have the same problem as you! I tried blowing into the main hole, in theory, nothing should pass through, everything should be sealed, or I'm wrong ?!)with your finger on the video, you are checking whether there is an air (pressure) leak somewhere
Yes, I put air pressure into the control valve (distributor) through the oil inlet to check for leaks. With the control levers in neutral the oil flow is blocked by the main spools and the unloading valve. The unloading valve is supposed to bypass oil when 284 psi is reached. Mine was only reaching about 240 psi. The air pressure I put in was only 100 psi so if everything was good there should have been very minimal leakage. As you can tell from the video there was quite a bit of air coming out. I assumed there must be cracks for that much air to bypass the unloading valve. The unloading valve itself looked fine so there had to be another way for the air to get out. A local wrecking yard told me that cracks in the travel circuits were common in these machines and that's when I decided to buy a new (used) control valve. Air also leaked from the new one but not as bad. I compared them to each other by putting a pressure gauge in the airline right before the air entered the control valve. The new one held more pressure. After installing it the new control valve reached the required 284 psi and the tracks responded much better. Hope that helps. Its a lot of work to take out the control valve just to test it with air but I had ran through every other test imaginable so it was the only option left.
did you lose the main relief valve or the entire distributor?
Thank you for the answer
I replaced the entire main control valve (distributor). The control valve actually splits into 2 pieces after removing the 4 big allen headed bolts. One side has bucket, boom, arm and auxiliary spools and the other has the main relief/unloading valve, swing and both travel spools. I think I could have gotten away with replacing just the side with the main relief in it but nobody is willing to sell just one half of a control valve.
thank you very much
So... just wanted to let you guys know that I have a youtube channel now. I sent a message to the moderators asking if I could announce it hear but did not get a reply so hopefully its ok. If you are interested you can go to youtube and search " EducatedGuessing Excavator Crane ". There are two videos so far, one showing the build and one for the testing of the crane attachment. I am just starting out so go easy on me haha!
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