When I boom down the engine wants to bog down and Stall if I done feather the control. I have the same problem with the dipper going out. I had guage on both pumps the one guage goes up to just under 5000 psi as soon as I use either of these functions. All other functions the gauges only go to 2000 psi, these functions are with no load. There has to be a restriction of flow for the boom down and stick out. There are lock valves in these hydraulic functions, could they be the problem? I have not put a flow meter to check the gpm yet that would be my next step. Does anyone know the gpm for those circuits? Are there any other valves that I should check. Thank you Mike 138.
Boom has holding valve, as far as I remember both have regen, at least arm does. Both have second spools. First thing I would do is to check return filter. Although last one I worked on with symptoms like that - ended up replacing arm cylinder and cleaning boat load of debris out of system, mostly out of ArmI and ArmII spools.
But I think the very important thing is the reason is why those get stuck!
You're right, the first thing to do is checking the return filter. Some reason can be cause of those get stuck are: Metal particles in hydraulic systems due to wear of the pump or valve. Water contamination in hydraulic oil.
How about this scenario: water contamination in the oil ( or other reasons of reducing of oil lubricity) for prolong time leads to the damage to the cylinders, which in turn spits debris in the system plugging stuff?! That’s why I said to pull return filter in my very first response!
I checked the return filter, I didn't have a lot of dirt and metal in it. I replaced it and changed the oil. There was some metal in the bottom of the tank stuck to the magnet. My book shows the boom lock valves at the base of the boom cylinders, they are not there. Is it possible they are on the control valve? I removed the boom spool it was clean , I know if I can locate the boom and arm lock valves I can repair them and get this machine up and working. Thank you , Mike138
in general boom lock valves supposed to be hard fastened to the cylinders ( usually bolted on or welded to the steel line of the blind end), because most of the times they are also hose burst valves. But I’ve seen on some machines that they are down behind cylinders bottom pins bosses, bolted to the frame. There’s also kits you can buy to convert those to whatever combination you think is better ( some of those come from crane booms) - so who knows who was there before you and what they did! One possibility: On those non standard kits - bad O ring around pilot port on cartridge can leak, and because of that you don’t get the pilot release when trying to move the boom. And your main lock valve supposed to be adjusted to around 130% of the maximum load capacity on the boom. And that will take some pressure to open that up. But it is only true for the boom down As it comes to arm - I am not sure it has lock valve(s)! But, never say never!
If my memory doesn’t fail me - there was Kobelco SK130 mark IV that had boom lock valve mounted to the side of the frame, all covered in the mix of the dirt, oil and leaves, nearly invisible under all of that. Just follow the hoses from the bottom of the cylinders.
The picture Lachau posted says it is in the main control boom section though. Take a look at that picture and see weather you have the same.
Check if for some reason you don’t have pilot pressure at port PLc1, on the diagram Lachau posted. That can cause the same problem.
They are installed at main control valve.
Hi Mike. When you have gauges on the two pumps and use arm out do both pumps go to 5000 psi or does only one go to 5000psi and other to 2000psi?. Arm out function with no load should show 2000psi on both pumps. If one pump is showing 5000 psi and other pump 2000 psi you probably have a faulty pump solenoid that is sending one pump to full stroke causing engine to stall
That is exactly what is happening. The one pump goes to 5000 the other 2000 and the engine bogs. I did change that solenoid because the old one fell apart when i took it off. there were a few choices in the parts book maybe i got the wrong one. This pump has the the single solenoid on the pump. the machine serial # YUO1-00298 have to check the part # or order a new one. It has power going to it, 24 volts. Thank You. Mike138.
Can you post a pic of the solenoid or can you read the numbers on the solenoid
Or post picture of the page on your parts book
Even if the part is right, the amps and pressures still need to be checked and adjusted.
Dear all, SK235SRLC-1 (YU01...) has one pump proportional solenoid valve and SK235SRLC-1E (have a E letter, YU02...& YU03... ) has two pump proportional solenoid valves. Therefore, the hydraulic control principle of the two models is different.
This one is the one “that got away”! Usually we tell OP to start with engine performance, then when totally sure that engine is fine slowly move on to EPPRV. This one went wrong, probably because OP proposed his own theory! It is my fault!!! I apologize! Kobelco Ireland saved it from dragging out too long
I don't think so. Anyway we should check return filter first, that is very simple and easy step. Regarding this machine, It has at least 02 problems: with BOOM DOWN and ARM OUT. Therefore I would like to step by step solve the problems. BOOM-DOWN problem. ARM-OUT problem.
Just pointing out that the whole sequence was started wrong.
You're right, I also think that should check 02 pump pressures. But I think it may be stuck in the main control valve. There are too many components can be stuck that can cause to make engine overload!!
What pump increase to 5000 PSI? P1 pump or P2 pump?? If P1 pump pressure increases that means ARM CONFLUENCE or check valve... can be stuck. If P2 pump pressure increase that means ARM LOCK VALVE or ARM RECIRCULATION VALVE... can be stuck.
Boom Down and Arm Out are both regen functions. If controls moving fast and NFC drops fast and EPPRV is out - you use full pumps flow. So pressure will go higher then other non regen functions. Should it go to full main relief pressure? I’ll be honest - I don’t know. Never encountered that problem before. I did had one Hyundai that was freaking fast as soon as you touch controls, and loading engine, but it’s owner decided that he doesn’t want to fix it ( at least at that time).
This is the 3rd different thread on this machine. First was no power in left track and arm which was solved but we were never told how by OP. we need to know this. Second thread was to do with rpm slow to increase, after A-adjustment this improved. Now we are on third different thread about engine stall from boom down and arm out. Maybe the first fault was fixed by replacing the broken pump solenoid with an incorrect solenoid which has now caused the engine stall due to over stroking the hydraulic pump. We first need to know how first problem was fixed and if stalling then started straight away or at a later date
BOOM-DOWN and ARM_IN (light load) has regeneration function. ARM_OUT doesn't have regeneration function.
Theoretically there’s supposed to be check valve, that will allow excess flow from blind end( because of difference of blind and rod ends volume) to go back to tank in regen. mode. If that somehow maul functions, it can cause pumps overload, but again should be corrected by the ECM through EPPRV.
OK, you right!
I didn’t know about previous treads! One thing to keep in mind - boom and arm may have different problems leading to same results! That’s why I am focused on the boom for now. If fixing the boom problem will fix the arm problem then good! If not, arm should be looked at after the boom problem is resolved. IMO!
Mike needs to firstly let us know if boom down and arm out give same readings on gauges, ie one pump 5000 other pump 2000,we then need to know which pump is doing which. We also need to know how he fixed original. Till we have these answers its just us guessing
Dear All, In the past, I came across a very funny case. The symptoms were exactly like this. This is due to wrongly connecting the main lines to the BOOM cylinders and ARM cylinder, the main lines to cylinders are swapped.
You absolutely right! Correct feedback is VERY important!!!
Did they also swapped out pilot lines?
Pilot lines were swapped at control lever ports!!
Ireland here are the photos you asked for. hope this is the key to the puzzle.
Lachau, yes only on the the pump regulators but i have tried all the different configurations and no help. There are only three lines that can be switched. I can"t find any thing in the book that shows how they are hooked up.Do you have that available to you. Thank You Mike138
Hi Mike the long number on the solenoid (kdrde5k-31/30c40) will be the same on all the proportional solenoids on your machine but the next three numbers are the important ones.,(101) on your is a number that is usually in either the arm recirculation, straight travel, or by pass cut. I have never seen 101 fitted as a pump solenoid before but anything is possible. Can you see the number on old broken solenoid.
Ireland, I can't read any of the numbers on try he old solenoid, to much paint on it. That number came out of the parts book but there were several choices, maybe it is wrong? Do you know the number for this pump setup.?
I will look into the part number in the morning. Try peeling the sticker off old solenoid and the paint should flake of it, it's would a try.
Ok, Thank You. Machine SR. # Yu01-00298
Your photo Proportional Solenoid Valve (PSV) is: YN35V00019F1(KOBELCO parts number); KDRDE5K-31/30C40-101 (KAWASAKI code) use for KOBELCO SK450_SK480LC-6' the other PSVs (P1_P2 bypass cut, ARM recirculation...), not for main pump PSV!! The right PSV of main pump for your machine (SK235SRLC-1) is: YN35V00018F2 (KOBELCO part number); KDRDE5K-31-30C40-111 (KAWASAKI code) fits for KOBELCO SK..."DASH" 6 (has no E letter) also. But anyway, I still think the main cause is the hydraulic-mechanical fault.
View attachment 227165
Lachau is spot on with the part number yn35vooo18f2.
With single PRV now it is important which pump is going to 5000. To understand which spool is a problem, boom I or boom II. does boom using regen. In all modes?
I ordered the new solenoid part #YN35V00018F2 waiting for it to show up. The pump that is going to 5000 psi is facing the pumps it is the one on the left. The one on the right goes to 2000 psi until it gets a load on it. Thank you,Mike
On the left side is P2 pump. It's source of Travel left+Swing+Arm (main). I assume it has been stuck on the load check valve "LCa" and / or the lock valve "CRa" .
Lachau, one of the problems I found was the auxiliary hydraulic pedal was stuck and I lost power to the left track and the stick in. I fixed that and got the power back to the left track and stick in. Now I have a problem with boom down and stick out, it is now making sense that one of the valves are stuck.. I still waiting for PSV solenoid but it will be here shortly. Thank you for all your help, Mike138
Last time you never said about history fault of this machine!! What auxiliary equipment is attached to your machine?? If it's a breaker, you should clean the hydraulic system of your machine very carefully. Breakers often cause the hydraulic system of the excavator very quickly to wear out and damage!!!
Lachau, this machine hasn't had any auxiliary hydraulic attachment on it for years. The hydraulic lines are jumped at the base of the boom for years. The medal lines for the auxiliary hydraulic are damaged and were leaking , that is why they were jumped. I think that I posted the preasure guage reading backward it is pump one the goes to 5000 psi as soon as you move the joystick for boom down or stick out. The guage on pump 2 reads 2000 psi for other functions, which is normal ,no load . Thank you, Mike138
Lachau, the operator must have stepped on the auxiliary pedal when he got in the cab, he didn't know that the pedal was unlatched, that when all of this started.
Mike, Please tell us how're the 2 main pumps work during BOOM-DOWN and BOOM-UP operation. BOOM-UP: 01 pump work or 02 pumps combine? How is pressure?? BOOM-DOWN: 01 pump work or 02 pumps combine? How is pressure??
Lachua, I will not get back to this machine till this Friday November 13,2020 the machine is oneand half hours away and rain forecast for a few days. As soon as i get there i will send the preasures. Thank You for al the help, Mike138.
Lachau, It is Saturday morning the rain finialy stopped. The new PSV solenoid is installed and i ran the machine and the machine functions are working better. boom down, no load, pump 1 3800 psi, pump2 2000psi. boom down load, pump1 5000psi, pump2 0000 psi. That is pushing the boom down to lift the machine up. Boom up,pump 12000psi, pump 2 3000psi no load, just the weight of the boom. Boom up rpm was 1900rpm and boom down rpm were 2200. Hope this gives you a better idea of what is going on. Thank You, Mike 138
Hi Mike, good to hear the new solenoid stopped the stalling problem. The reason boom down has two pump flow in free fall and only one pump flow when trying to lift the machine is so that in free fall two pump flow stops cavition in boom rams and when pushing boom down to lift machine it only uses one pump
Hi Mike I might be wrong about double pump flow, I am only going from memory and it's been a while since I worked on a 235-1
@Mike 138 , I really wonder when reading the information you give. It is completely wrong with the working principle of the SK235SR!! I guess your machine has many hydraulic hoses wrongly connected. Let me send you the repair manual of this machine so that you can check again the hydraulic hoses, pipes and reconnect them properly.
Yes, I know that. Main pump pressure equal to Negative Controlled pressure when main pump is inactive. It's around 35 bar (500 psi). I know that. But can you read it clearly with 500 bar (7000 psi) gauge?? I said like that let Mike 138 understand easily.
Lachau, what if the lines from the pumps were switched would the readings make sense then. I don't know if anyon3e vbefore me changed them? The manual that i am using does not show the pump and valve set up that this machine has. Can you send me a copy of the correct manual for this machine. I will be back at this machine on Friday and i will take the main pump inactive readings. should both pumps be at 500 psi or only one? The only other thing is the pilot lines that go from the pump regulators to the control valve could be wrong, there are three lines and i don't have a picture in the parts book or the manual that shows the way they are hooked up. Thank You, Mike 138.
Control Valve Pn1==>Pi1 Pump 1 regulator. Control Valve Pn2==>Pi2 Pump 2 regulator. Control Valve Tn2==>Pb1 Pump 1 regulator. Control Valve Tn2==>Pb2 Pump 2 regulator.
Lachau, worked on the machine today. Checked the pilot hoses from the control valve to the pump regulators, they were wrong, I changed them to the proper locations. The machine functions are better but all functions work better when you full stroke the joystick, if you feather the joystick in all functions the machine bogs down and wants to stall. I have some video of the gauges I had on the pumps I will attach them. The other thing the pump standby pressure on pump#1 is 1000 psi you stated it should be 500psi just thought that was odd.
My video files are to large to send. There is a two wire sensor on the boom pilot control actuator, I don't know if this sensor is bad, the outside plastic is cracked I will include a picture. I will also post the pressure guage readings from today.
My God!! More and more difficult each time!! This is pressure switch which indicates that the machine has been installed a nibbler!! The option hydraulic circuit is more complicate!! The pilot hoses of main control valve may be wrong and/or optional valve has been stuck!!! It may be "P1 bypass cut spool" stuck!
Or someone adjusted minimum displacement on that pump all the way. I had Hyundai 350 doing that - that thing was as fast as freaking rocket as soon as you touched the controls! Also orifices at NFC relief can be plugged - I would check that first.
The problem with this machine is if you move the joystick part of the way the machine bogs down the the functions are slow. If you move the joystick full stroke the machine functions fine ,plenty of power and speed engine doesn't bog . I have been working on this when I can and have been following the posts and checking all the suggestions. I did change the hydraulic oil and filter, the only thing is I got an aftermarket (Wix) filter it was the same size but I don't know if it is rated for the GPM of this machine. Has anyone run into this? I feel that there is a restriction in the return flow to the tank and when you full stroke the joystick it pushes the return filter into bypass. Just my thoughts. I have a flow meter that I haven't hooked to this machine but I can get the flow at the pump but I think it is in the return to the tank. Had anyone seen this type of problem. The main thing I found that one of the auxiliary spools were stuck I removed cleaned it and is fine now. I checked this because the original problem was the auxiliary pedal was stuck with limited power to the left track and stick in. Thank you ,Mike 138.
If it was the restriction in return then it would bogg down the engine all the time. What you described is the missmatch in pumps flow to spool position in the main control valve. The flow request is done by drop in NFC pressure ( two 1/4” lines from each side of the Main Control Valve to each pumps regulator respectively). At neutral there supposed to be a stand by pressure in each line, when you start to move the control joystick, then pilot pressure from control joystick should start to move the respective spool in the Main Control which in turn should start blocking the Center gallery and drop the NFC pressure proportionally. If your NFC pressure drops abruptly ( not proportionally) right after you start moving the joystick - that might be your culprit! But first you have to be absolutely sure that everything is connected right. if there was catastrophic failure to the main system component prior, which put a lot of debris in to system, I am afraid you going to have to go through the whole system. One peculiar case was in my experience, when case drain filter was mounted backwards, and plastic bypass valve broke in two, and one half of that was blocking all the flow. But because you said machine works fine in full stroke of the joystick - I don’t think It is you problem. Although checking functionality of the bypass valve of return filter is a good idea, just in case.
1/- This main pump regulator is controlled by: "DIFFERENTIAL PRESSURE" (Flow rate increase when decreasing Pilot differential pressure (Pi-PB) = Pilot pressure- Pilot back pressure). If Pilot's back pressure rises and stays at high, the DIFFERENTIAL PRESSURE becomes out of control. Hence, I suggest to check the return oil path as below image. 20 = boost check valve. 21 = by-pass check valve. Including the oil cooler check. 2/- Another reason is that the regulators of the main pumps have been replaced by the improper regulators.
Also bypass cut needs to be checked out.
If the pump regulator fork was not attached to the pin inside the pump correctly it could cause high stand by pressure and would allow pump to full stroke as soon as lever was moved. I am also wondering was the engine stall problem in this machine before the original problem of the stuck auxiliary pedal or was the stall problem created while trying to fix original problem by something being incorrectly attached. Are the high pressure pump sensors connected correctly se-22 to pump 1 and se-23 to pump 2
Oooo! Yeah!!! Good old “missing the pin when shhlapping the regulator back on”itis. Also might be “loose clamp on servo piston”mia!!! And yes - that thing sounds like Super Mega multiple offenders deluxe!
The best opinion. I have come across cases like this in the past!! But long time no see that I forget it!! ".. regulator fork (feed back lever) was not attached to the pin inside the pump (pin on servo piston) correctly it could cause high stand by pressure and would allow pump to full stroke as soon as lever was moved"..... The consequences are that if you move the joystick part of stroke the machine gets bogged down, functions will be slow. If you move the joystick full stroke the machine functions fine ,plenty of power and speed engine doesn't bog!!!
@Kobelco ireland , This is a very interesting case of digging into the K3V series pump regulator working on the principle of negative flow control (NFC). The next question would be: Why can't the main pump regulator reduce the flow to avoid overloading the engine when control lever operate at a part of stroke. While it is still possible to reduce flow to avoid overloading the engine when control lever operates at full stroke??
I don't think its reducing the flow at full lever stroke but more likely that because the spool is fully open the the oil can flow unrestricted to the cylinder. Once the cylinder reaches the end of its stroke it should pull the engine down again but Mike will have to confirm that for us
Protection of the engine from overloading is a job of KPSS through EPPRV. Inducing load while operating Arm is a load that takes to move arm and bucket ( and dirt), plus back pressure in return passage/circuit. And normally there supposed to be next to no resistance in return! There’s also matter of regen. Function which is inducing extra load by design. If one of the pumps constantly having excessive stand by or neutral pressure - I would seriously question weather the feed back pin is in its proper position inside the fork, weather clamp on the servo piston is in proper position and tight, and finally weather the minimum displacement screw is adjusted properly. And BTW the question about engine performance is still open!!!!
Sorry, This is my mistake!! I said not clearly!! I want to talk about the overload prevention function of the regulator by the pressure compensation system (piston compensation, lever, transmission rod, 02 springs). Why can't it work properly? When the pump pressure P1 is increased, even when the feedback lever slips out, the pressure compensating piston still pushes the pressure compensator lever to the right, causing the spool to also move to the right to open the pressure oil path to the larger chamber of the servo piston ==> decrease tilt angle ==> reduce the flow of main pump.
The machine is fixed. I can't thank all of the members for all of your help. Lachau, Kebelco Ireland and TVA for all your help and patients. It is always a nightmare when you work non a machine after someone else worked on it and left it . I found out they had the pump regulators off that is why the hoses were hooked up wrong on them. The first thing i looked at today was remove the pump one regulator and put it on the pin and all functions worked and engine did not bog . Thank all of you, Mike138
That's great to hear
Congratulations on your successful repair of that excavator. Machines that have passed through the hands of other repairmen are often difficult to diagnose.
Good to hear that!!!