We're experiencing a strange problem with my 800C. After working it for a bit and it warms up, it starts to slow down on all hydraulic functions, including swing and travel, until after an hour or so it's so slow it only makes sense to stop digging. It's as if something is wrong with the pilot control system? As described by the operator, it's like every function is "governed down", and the longer you work it, the slower it gets. So far, we've changed all the hydraulic filters, I've swapped the regulators from one pump to the next, and replaced the vehicle controller just yesterday. Also, there are no trouble codes being shown by the LED indicator. This machine runs fine, engine wise, and no obvious problems with the pump - pressures are normal and there's no noise or metal shavings in the filter or anything of that sort. It's not an engine problem, because the motor runs perfectly, no surging or anything of the sort. I can't see it being that the pumps get weak simultaneously, as these machines have two pumps, each of which supply a travel motor, so when one goes or a regulator sticks, etc., it usually creeps to one side badly, and it's not doing that. I'm starting to think it's the pilot pump going bad, but I'm not sure I want to just keep throwing new parts on it to see what fixes it. We've been chasing this ghost for weeks now, so any help would be appreciated. Thanks!
It could be a bad pilot pump or regulating valve. Have you looked at the pilot pressure when it acts up? Be sure the engine is running at full rpm I have been to lots of calls that it turned out to be a fuel issue. There's a screen in the inlet at the injection pump that plugs up quite a bit.
Just checking, you have changed the small pilot filter coming off the gear pump? Do check the pilot pressure cold and after it gets warm and slows down. It looks like the pilot pressure is also plumbed to the pump regulators so low pilot pressure my cause an inability to stroke the pumps as well as shift the valve spools completely. If the pilot pressure seems correct, try checking it at one of the joystick supply ports, there may be something restricting the flow, like the safety cutoff valve connected to the safety lever, wherever that lives? If you get low pilot pressure, just for giggles disconnect the small suction line at the gear pump and make sure there's no restriction in that hose, pretty long odds but the hose could be coming apart inside or have a small bit of debris stuck in it starving the pilot pump.
Thanks to both of you for your input. I have changed the pilot filter and I'm certain it isn't the engine slowing down. We've checked just about everything now, including simple stuff like the precision mode switch and the counterweight removal sensor, etc. It's looking like a pilot system pressure problem. I'm thinking that at 13,500 hrs, the pilot pump might be giving up the ghost. It just loses speed, not power, as it warms up, until after an hour or so it gets so slow that we just have to stop working the machine. We installed a pressure gauge on the pilot system this evening, but it was too late to run it long enough to check it. Will check it in the morning to see if it's making the requisite 550-600 psi when it warms up and report back what we find. Thanks again.
By way of an update on this: we've now tested the pilot pump pressure and it seems to be within the specified range. However, after relying on "mechanics" to try to troubleshoot this ghostly problem, I decided to do a check over of the machine myself this morning and found that the hydraulic oil temperature was shown as 90 Celsius (!) at start up!! I guess either the guy who I hired was reading that 90 degrees as Farenheit and thought that was normal, or he didn't bother to check. The temp readout on the gauge cluster is actually showing the temperature fluctuating between 88 - 94 degrees C, and will deviate up and down within a few seconds, so it seems that the sensor is faulty? I didn't work the machine, but can only imagine that if it starts off at 90ish instead of 35ish (i.e. circa ambient air temps this morning) then once the machine warms up to normal operating temps, the sensor must be telling the PVC that the hydraulic oil is overheating??? I'm thinking that may then put the machine into reduced power mode?? Is this how it works? I'll get my operator to work it tomorrow to get it to operating temperature and see what it reads then. Thanks again for any advice offered.
This morning we exchanged the hydraulic temp sensor with the one from my 450CLC (same sensor) and that displayed 73 degrees C (which seems odd, as the ambient air temp here is around 33 degrees C today) at start up and when we worked the machine this morning, the machine is doing the same thing, getting slower as it gets hotter. However, the hyd. oil temperature only went up to 99 deg. C, which I can't see as being so high that the PVC then goes into reduced power mode??? This thing has really got me stumped. The real problem I have is that no one is this country has any specific knowledge about this machine and I cant find a diesel/hydraulic mechanic that has the necessary tools to properly diagnose this machine, so it's starting to look like I'll have to fly in a tech from Nortrax in Florida to troubleshoot this problem.
Is there a way to calibrate that temp sensor? Maybe you have a computer error or a bad connection in the wiring? 99C is over 200F so maybe.... Maybe read the resistance of the sensor cold and put a fixed resistor or adjustable pot in the circuit instead of the sensor, fool the computer into thinking the oil is cool?
Thanks. That's a good idea. I'll look into that. 99 degrees C is like 210*F , which is a bit hot, but I'm not sure if it's hot enough to send it into low power mode?? I really don't know much about these things... Here's the thing, the machine doesn't seem to actually lose power, it only slows down (so my thread header is actually a bit misleading!). Based on what the operator is telling me, it can still lift itself off the ground, so it's not weak, it's just very slow on every function. He describes it as "if you're not pulling fully on the levers". And this applies to every function, including travel. But when it starts up cold in the morning, its fine and as fast as normal. Then after a half hour or so, it starts to slow down. It sounds like a pilot system problem to me?? and one that is temperature related. We've checked the tank for air bubbles and all of that as well, because we had one suction hose on one pump that has a bad rub on it, and I thought it may be pulling air into the tank.
Have you tried putting a gauge on the pilot supply line at one of the joysticks? The pilot system shutoff valve that is somehow connected to the safety lever, is that mechanical, electrical? The shutoff valve could be your problem, wherever it is.....
Thanks for this. We've tried that now and the pilot pressure is the same as at the filter housing (~550psi), so we've ruled out the pilot pressure as the culprit. We then tried using a number of different resistors in the temperature sensor harness and I think there's something definitely wrong with the harness: According to the service manual, a resistance of 5880ohms equates to 0* C and a 16800 ohm resistance equates to -20*C, so I would conclude that the higher the resistance, the lower the temp should read on the gauge. So, we pulled the plug off and took a reading with the wire disconnected and it still showed 84*C on the gauge pod?! I would've thought it should zero out or show a really high temp?? I then inserted a 5600ohm resistor and the temperature went up to 87*C! Then, just to test it, I inserted a paper clip in the plug and it went to 120*C, which shows that the lower the resistance the higher the temp. I guess 120*C must be the upper limit? Then I used a 100,000ohm resistor in the plug and it showed 84*C - the same as with the wire unplugged!!? No matter what we did, it wouldn't show anything less than 84 degrees. Then, when we started the machine up and started to run it with the 5600ohm resistor plugged in, it went down at first to 74*C and then fluctuated between that and 86*C and then rose from there up to 99*C! This is with the wire completely disconnected from the sensor with a resistor plugged into it! WTH? I traced the wire to where it goes into the main harness, and there are no obvious signs of damage, so I don't know what to make of this. This machine is really giving me a headache!
I would think that with an open or shorted you would be throwing "out of range" error codes. Maybe you need to look at the harness connections to the computers, pull them off and check for moisture or corrosion, wiggle them on and off a few times, maybe some electrical contact cleaner spray with a toothbrush followed by dielectric grease. Sounds to me like you have some corroded contacts which may be having some crosstalk to ground issues? Just a guess. Of course you still don't know if this is what's causing the hydraulic issue?
Thanks. I'm thinking the same thing. I'll clean the PVC and harness connectors and put some dielectric grease on them as well and see what that does. I'm going to also swap the PVC again back to the old one and see if that makes any difference. I'm doubting as well that this could cause the hydraulic functions to all slow down. Another thing I noticed yesterday when we were testing it was that if you hit the power boost button, the engine instantly slows right down to idle and stays there until you hit the power boost again to deactivate it?! I have another mechanic coming this morning to check it out, so I'll see what he says - that is, if he doesn't just scratch his head and then run away from the problem like the last guy did!
That sounds like you have a short somewhere in the 5 volt sensor circuit. Power boost and auto idle circuit souldnt be connected. Probably needs a harness. We put them into 800s all the time. As for sensor calibration, there is none. What are your codes on the pvc through the monitor not the flashing light? As for it slowing down when its running have you checked your piolt pressure at the spool when it acts up? I have seen piolt controllers do exactly what youre describing. Also your piolt pressure is low, should be 565-710 psi at fast idle.
Thanks. That makes sense. Are you talking about the main harness that runs from the pump room forward to the cab? When you say "pilot controller" do you mean the PVC as in the computer behind the seat? We just installed a brand new one from Nortarax and the problem is still there. We've checked pilot pressures at various locations and it does seem a bit low. I've also noted that it doesn't get any higher, whether at fast idle or WOT. Unfortunately, the gauge we have has a wide range (up to 5000psi) so we can't accurately read pilot pressure. It reads between 500-600psi. The tech I spoke to at Nortrax said that anything over 500 was good, but I do see in the Test Manual that it should be at 565-710psi at fast idle. I'll check the pilot pressure at the spool, because I don't think we've done that as yet. There are no service codes shown on the monitor. The thing is that the engine runs like a sewing machine and the machine still has power - it can easily lift itself off the ground. It's just frickin slow and gets slower as it gets warmer!? What I really need is a good hydraulic mechanic that knows something about these machines. But we don't have one of those around here, unfortunately. Thanks again for your advice. I will most likely order a new harness and I'm thinking that I may as well change the pilot pump while I'm at it. This old machine has served me well over the last 4 years. We've dug well over 500,000 CY of blasted rock with this machine, without any major repairs, so I think she deserves whatever new parts she needs.
I would throw some fuel filters at it and inspect the fuel supply. It could very well be a fuel starvation issue, still getting enough fuel to run just fine but over time it could be sucking debris over the inlet or just not getting enough fuel through the filters. Good luck!
Yes the main machine harness, cab back. Hitachi harnesses don't like heat and cause all sorts of breaks because the wires are too small of gauge. As for the pilot controllers I am talking about the valves inside the cab where the handles are attached to. Could be a issue in the pilot signal manifold too but unlikely. You definitely need to shim the pilot pressure regulating valve because it will be approximately 100 psi lower by the time it pushes that spool down. 485-570 psi. So with you get 550 psi at the pilot filter then you only will get 450 at the valve and that defiantly could cause issues as the pump regulators need pressure to work. If you cant get 710 psi from that pump you have a problem. They use the same pump for a low flow auxiliary kit and it can hit main relief pressures 4500 psi appox (off the top of my head) From the service manual: If spool actuation pressure is low and if pilot pressure regulating valve is set to specification then check pressure at the pilot shut-off valve, pilot controllers, pilot signal manifold, pilot check valve manifold, boom down flow regulator, and solenoid valve manifold. Just a note about dielectric grease, it should never be applied to the terminal but rather around the seal. Dielectric grease will cause codes if on the pins. I have seen it multiple times. Clean the connector of the dielectric grease and ghost codes disappear.
Ok Thanks very much sir! I start today by shimming the pilot regulator valve to see if I can get the pressure up to ~700psi and see what that does. If that doesn't work, I'm going to put in an order for a pump. I think I will order the main harness (which Nortrax lists at over $3,000!) as well and the smaller harnesses that connect that to the oil temp sensor and solenoids, because this strange temperature reading and the power boost-forced idle issue probably mean that the harness is bad? I have noted that the gauge on the wires on these machines seems really small. The wires on the temp sensor are like 20 gauge, if not smaller. I seem to recall as well that someone told me a while ago that if the counterweight removal sensor is bad it can cause a problem with the pilot system as well, so I will also order that sensor just to be safe. I get the dielectric grease thing. I've seen folks use that stuff liberally on connectors as if it increases conductivity, rather than sealing out moisture. I guess they don't get the DIE electric thing. I have a friend with a Cat 300 that cured a bad engine miss that he had for months by just using some dielectric grease to seal his injector harness though. He became a great fan of dielectric grease after I told him how to use it to try to fix that problem. He probably uses the stuff as toothpaste now! Lol! Thanks again for all the advice. It is greatly appreciated.
Thanks very much for your advice, AndrewC! We shimmed the pilot regulator this morning using 3 5/16" flat washers and got ~700psi (on the gauge I have - gonna try to get a better one tomorrow), and the machine has been working all day!! Can't tell you what a relief that was! Can't believe that after all of the frustration chasing this problem, all it took was three little washers to fix my machine! The operator says that it still slows down slightly when it warms up, but is much faster than before. He's saying that it still has a quirky little problem, in that, sometimes when he swings the machine, it swings slow, but if he booms up or booms down slightly, it will speed up instantly?? Anyone have any idea on what that is? I'm still going to replace the harness, as I think that is the cause of the oil temp issue and possibly the power boost forced idle as well? Thanks again to all who offered advice. I greatly appreciate it.
With all the money spent on replacing parts, you could have flown somebody to your machine and actually fixed it instead of changing parts and still be money ahead. At least you are asking the right questions and there is a lot of knowledge here to be taken advantage of. No such thing as a dumb question IMO.
Well, actually, no. Even with what I spent on parts that I didn't really need, it would've still cost me a lot more to fly someone in, put them up in a hotel, etc., especially since I would have to apply for a work permit for them and pay them for travel time, etc. Not to mention the waiting time and the documentation that I would've needed to obtain for that. If it were that easy, I would've gladly brought someone in long ago. We have guys down here that work on these machines, but mostly Cat and Komatsu machinery. The mechanic I had working on the 800C at first is a decent diesel mechanic, but he doesn't have the experience, tools and manuals to really work on Hitachi machinery. I have a friend who brought in a tech once from Nortrax to troubleshoot a hydraulic problem he had on an EX750, and he says they sent him a bill for around $12,000. It's not easy to run this kind of business down here, especially when you have to import everything, right down to grease and hydraulic oil, if you want the right stuff.
when you say the machine slows down is it every function? When it is slow does it track in a straight line if you try to travel? You said when it swings and is slow and boom up it speeds up, that sort of sounds like one pump is not stroking as swing is a sngle pump function and boom up uses both. If memory is correct this model has the pilot shuttle block behind the cab to activate the pump when a function is selected. I didn`t go back to every post, but I think you mentioned switching off heavy lift function. There should be no on/off switch for heavy lift as it goes through the controller to only be on for 4 or 5 seconds then the pilot oil to the relief valve is cut off. Not to sound like a ----, but your time would be better spent as well as your $$$$ if you keep asking questions here before you order parts. My $.02
H Yep, it was slow on every function. It tracked perfectly straight, just very slow as well, along with every other hydraulic function, once it warmed up. It functioned normal and was fast when it first started up in the morning, but would slow down after working it for a half hour or so. That's been cured significantly now by the increase in pilot pressure to ~700psi (indicated on a not so good gauge, on "out" side of the pilot filter. But now it has this weird slow swing until you just hit the boom up or down. I'm hope I'm not wrong, but I don't think it's one of the pumps, because I would've thought that it wouldn't track straight, which is what happens if a pump or regulator fails. We had a different issue a couple of years back where it would lose boom down power (as opposed to being slow- it couldn't lift the machine) unless you just barely touched the travel lever/pedal and then full power was instantly restored. That was diagnosed to be the boom regulator (located under the floor of the cab) which I ultimately replaced, but before I installed the new part, the problem solved itself somehow. Trust me, I do value these forums as a very valuable tool as there are very knowledgeable people on here, and I wouldn't buy parts unless I thought they were needed. It's just that the "mechanic" I had first told me that it could be the pump regulator, which we've had problems with before, and was in fact very dirty inside, and so I bought that, then he said it had to be "the computer", so I bought the new PVC. Then when he installed the new "computer" and called me and told me it didn't work, because it turns out, he had not performed the relearn procedure (even though I had loaned him my repair manual), I decided I had to try to fix it myself, instead of paying someone who obviously didn't know what he was doing. Hence, this thread. Many thanks for your input.
JHESL, there is a couple things that could do that to the swing function. Im wondering if the pump two flow rate valve is sticking but you should put a gauge in the pilot line to the spool and see what happens when it acts up.
Thanks again for all the advice AndrewC. We've been pretty much keeping a gauge connected to the out side of the Pilot Filter housing for the last couple of days, because its acted up again a couple of times lately and then when it cools down again the problem goes away, sometimes for a whole day. The operator says that the pilot pressure is steady at 700psi (at the filter) even when it slows down, so I don't know what to make of it, except that it may be something sticking on the spool or the PVC is commanding it to slow down due to there being some electrical/harness issue as indicated by the hydraulic temp faulty reading issue??? I'm going to take your advice move the gauge to another location closer to the spool and watch to see what happens. I just haven't had a chance to attend to it myself as yet. Not sure what to make of this. If this keeps up, I may very well try to find someone to fly in and give the whole damn machine a thorough going over. Where are you located? How about a nice vacation with some hydraulic system troubleshooting thrown in?
Yeah, your going to have to put a gauge at the spool pilot line and work back to isolate it. I still would think a code would be generated if the harness was being weird. I'm up in Canada and I do work for the dealer. I'm sure my boss wouldn't mind that for a couple weeks it is starting to cool down up here too.
Ive had a gauge on a machine for a similar issue for two months now. It hasn't acted up since