Hi everyone, Here is a description of what happens with my excavator I recently bought, if any one has any idea's that would be heaps good. I asked komatsu and they spoke of it as*a 'hydraulic issue' and asked if i have gauges or fittings to do tests*(which i don't) As a guess i would think its a sticking*valve or something going to the final drives but don't really have a good understanding of where anything is on the machine not knowing much about hydraulics or excavators. The excavator is what i am told is a grey import, and its a komatsu PC30MR-1 When using the machine (once its warmed up) when i stop moving*it, the*revs drop down, and sounds like it is going to stall or droped down sounding underload, then when i start moving the revs go back up, like something is sticking or blocked. It will happen almost every time i stop, like the motor or hydraulics is under load or blocked. I can get the revs go back up to normal by moving backwards and forwards a few times. While stopped when it does this, with the revs low or under load if i move the throttle to increase the revs it has no affect on the revs, and will only change the revs once moving again. Also if anyone info on this model that would be usefull or a service manual that would be awesome as the bloke I got to service it couldn't find a hydraulic filter and just told me they only need replacing every 5000hrs which doesn't seem right to me. Thanks.
Also I forgot to mention, it seems to work fine until after about an hour when its warmed up.
Sounds like your loading up the pump when you stop. Does the engine speed pick up if you move anything else other than the tracks? Adam.
Nah I tested that trying to lift the machine of the ground with the boom while the machine was sounding under load, but it almost stalled so I stopped. I could be rong but it definitely seems to be linked to the driving hydraulics, as im pretty sure if stayed in the same spot digging for an hour or more it would probably be fine until I started moving around.
That being said it seemed strange to me that if I move the throttle to increase the revs while it is doing this it didn't increase the revs but I spose if the pump was loading up the motor might not be able to over power it?
There's a website called tradebit that has manuals for everything. I bought a manual for mine off there. Might be worth a try.
Thanks Ads I will have a look. In the meantime does anyone know if there is a valve or hose that is a potential cause? I keep looking at the machine in an attempt to see something that needs cleaning, that I could do myself without spending more money getting someone to look at it, but all I see is a bunch of hoses and don't know where the valves are let alone weather I should be messing with anything?
Where abouts in Aus are?
Kenthurst, NSW
I lived in Richmond for a while but I'm up in Newcastle now. Have you had any luck with the service manual?
Yeah I had a look on that site and found one for $44US, and one that is only $14 but that is a mrx-1 so im guessing the x stands for something different, so I think I will get the expesive one. Yeah richmond is a nice place I was looking at buying land near there a few years back but was a little to expensive, I ended up buying acreage in cattai, and thats mostly why I bought the excavator.
Is your whole excavator performance under-load? That`s might be your gear pump problem OR your valve plate`s surface polish..... If your excavator track performance suddenly blocking ..The problem might be your center joint problem...Because the seal inside in the center joint has been spoiled, so the hydraulic oil cannot 100% go through to the track motor...Therefore, the track motor sometimes received the hydraulic oil just only half or little that will make your both(right&left side) of the track motor perform not well...
Louis yao, it is loading up the whole machine, but only when i stop moving, and only when its hot or warmed up after about 1 hour of use. When i stop it's like the oil is blocked off to the tracks and is causing motor to bog down an have no power, but as soon as i am moving i can swing the boom and everything seems normal, It doesn't seem to have any trouble with the actual track performance just some sort of blockage when stopped. Hope that describes it better.
The machine has a closed center load sensing system. Basically there is a passage between the main control valve outlets to the functions and the LS valve on the pump. The LS valve tries to maintain a slightly higher pressure at the pump outlet than what is seen at the outlet of the main control valve. When I was working on the bigger machines the differential was 300PSI give or take. It sounds to me like you have a problem in that LS valve. They are usually a cartridge that plugs into the pump but not having worked on your model machine I don't know where it is at. Were I working on the machine I'd find out where that cartridge is, remove it and take it apart checking for a broken spring or a worn seat on the cone. I'm sure you can purchase a new cartridge if necessary. You couldn't purchase parts for that cartridge in the days when I was working on Komatsu stuff. The other possibility is the swash plate in the pump is stuck on stroke due to a mechanical issue. There is a servo piston that moves the swash plate where debris can get stuck in or behind. I haven't pulled one of these pumps apart so can't tell you just how to check that without removing the pump and tearing it down. You need a book and plenty of study time if you wish fix it yourself. Generally these kinds of issues make the dealer wrenches scratch their heads and take plenty of time and money to figure out.
Thanks for the info John C, It looks like I will need to buy that manual asap and get studying, I was hoping it would be something simple like cleaning out a blocked part, but seems like its probably a pretty complex problem.
Hi, John C. Is this PLS part 'control valve LS pressure inlet the sameas the LS Valve you were speaking of? If so, can a novice like me take this apart without causing any big problems? If I disconnect the hose will I have to plug them to stop the oil pouring out? Ps that photo of the pump should be rotated clockwise 90deg to be the right way around.
I'm not familiar with that pump so can't say for sure and don't have a book on this machine. It does look similar to the old LS valve cartridge that was in the PC200-6. I suspect you can remove it to check it out. It will drain oil from the tank when you take the hose off so you will need to plug the hose. The cartridge for a LS valve usually has two lock nuts and the valve itself adjusts by turning one body inside the outer body that screws into the pump. When you remove the entire valve you will get a bunch of oil so have a rag or maybe one of those rubber expansion plugs to put in the hole.
Just an update, I pulled the LS valve out of the pump today. I couldn't find anything wrong with it, but the manual didn't seem to have the spring lengths for that valve, so hard to tell if they were still the correct lengths. One thing I did notice though, the bit that was attached in between the valve and the hose, a presure gauge adaption bit had a hole only the size of a bees d!ck Probably only 0.7mm, and the hose and valve had a hole atleast 3mm. Could this be restricting the flow? I've got a photo of it but forgot how to post photos.
Found it. If anyone can let me know if this tiny holed pressure testing bit closest to the camera needs to be there I would appreciate it. I can take it off and hook up direct from valve to hose.
It needs to be there. Make sure it is not plugged. Just another thought is have you removed the hose that hooks to that and goes back to the main control valve. Make sure it isn't plugged with something or leaking externally. I don't recall Komatsu ever providing a spring length for a hydraulic component. They are basically designed so that with the knowledge and right tools the components can be adjusted back to factory specification when performance drops.
Hi john, had a look at the hose and it looks like it would be a bit of a job to disconnect and re connect so haven't done that yet. Are you sure about that pressure testing bit being correct to be on the Ls valve? Here's is a drawing of the pump I found and its not on it and can't find the part anywhere in the in manual. Do you think it could be the main relief valve? I can get to that cartridge fairly easily, if you think that could possibly be the problem? I ran the machine yesterday after putting the Ls valve back and ran it for 3 hours and noticed a few more points that could be helpful in diagnosing the problem: The machine didn't start malfunctioning until it was up to 80 degrees C which took the 3 hours to get it up to about that because of the colder weather but earlier that week it got to 90C in 40mins because of the extremely hot day and was malfunctioning the worse than ever, so without a doubt the temperature is triggering something. The Ls valve is set to maximum pressure in adjustment and the Pc valve is set to minimum seting. The two valves could not be adjusted much if at all in those directions. When the machine is still in the warming up process, when traveling I can let the levers off and the machine will stop as normal. But when doing this when hot 80+Cels the machine will stop more abruptly. This is what leds me to think it could be the main relief valve, as I think thats the one that would relive the residual pressure, but not really sure just a guess. What do you think?
The temperatures you are stating seem a bit high. What is the temperature of the environment you are working in? Have you checked to see that the radiator and hydraulic oil cooler is clean on the outside. Has the engine been running warm at all?
Both the oil cooler and coolant radiator are not in great condition, and I will get new ones or recondition them as the previous owner has pressure cleaned them and have bent fins over about 30% of each. The day the machine got to 90deg C is was 39deg C outside, and i was running the machine in the sun. And more recently it was only 22deg C out side, and the machine wouldn't go over 80C The original bar type temperature gauge is very hard to see, so i had a analog gauge installed that tells me the degrees. 80C = is about the middle of the green on the original bar gauge. 90C= is getting close to the red but still in green. Now thinking about it both those gauges only measure coolant temp, its not really telling me what the hydraulic oil is. How hot is the hydraulic oil meant to be? I know when the machine is hot, the hydraulic pump is pretty hot similar to engine temp. I wasn't going to fix the radiators until I had the problem fixed, as this would be hard to see if the problem was gone when i cant get the machine quite hot enough. Or do you think the oil getting hot could be the problem? I was thinking its probably more of a trigger to the problem. I'm under a bit more pressure to get it fixed and reliable now, i have about 2 weeks work digging trenches for a customer i am meant to start mid next week, but I'll have time this week to work on it.
If you know anyone that would have a laser thermometer, run it up to temperature and see how even the temperature is over the radiator and the cooler. If it's fairly even it could just be the thermostat.
Here's an update of what I've done: Took out the LS Valve, LS bypass plug and relief valve, they seemed ok. Today I think I Had a bit of a breakthrough, I adjusted the relief valve one turn to lower the relief pressure, and it ran better!! the things I noticed were: The machine wasn't stalling when using the equipment when the revs droped. The revs didn't drop down nearly as often. I think i had a little less hydraulic power. The revs were still dropping down but the machine was much more usable. Im not sure if just all the pressure settings are all screwed up, anyone know if i can hire the gauges to do the tests myself? Or I could lower the relief valve even more and the problem might go away. But I'm a little hesitant to go crazy changing the settings to much.
Last sunday I changed the hydraulic oil, filter and strainer and the tank was full of crap this is a pic of the strainer at the bottom of the tank. I cleaned the tank out and found it was a coating on the inside of the tank flaking off, everything above where the oil level is. Im thinking this oil is getting way to hot, I don't have a thermometer to check but put my hand on the radiator and then the oil cooler and the radiator is warm but the oil cooler is dam hot, and can't touch it for more than a second without burning me, the hydraulic pump is super hot too? How hot is a pump spose to get? It's worth noting spend hours straitening the fins on the oil cooler and its in in real good condition now so would expect it to be that.
Just thought I check see what people think of the condition of this main relief valve cone. It has a slightly worn ring on it from where it sits in the seat, I just looks superficial to me, but thought I might ask some people who actually know. I can machine it down if necessary.
Is the trash on the strainer metal and is it magnetic? Can you feel the ring on the cone with your finger? If you look at it with a magnifying glass is it perfectly round? In my experience the hydraulic oil should run a bit cooler than the engine coolant. I use an infrared thermometer when doing those kinds of checks. Skin usually only tells something is cold, warm, hot, real hot and then it burns. Doesn't give you a good read on actual temperatures.
The junk in the tank was pain or whatever they line the tank with. There wasn't anything magnetic I checked. I spun the cone in a drill and its perfectly round, the ring on it is barely enough to catch with your fingernail and pushing into the seat by hand can't feel it causing any sticking or binding. I might be able to find a manual thermometer and wire it to the oil cooler, would that be the best place to attach it?
I've use an oven thermometer in the days before I got the infrared. I kind of works when touching duct taped to one of the tanks but the infrared is the best way to go. Enough junk in the strainer could cause bubble implosion in the piston and barrel assembly making for leakage and a lot of heat. If you are still getting that heat you are probably in line for at least tearing down the pump and inspecting the parts. The cone sounds to me to be OK.
Good idea, I do have one of those oven thermometers somwhere so I will try that out and see what it reads. If it comes to having to take the pump off it might be worth my time to leave it to the professionals, but hate the idea of leaving it at komatsu letting them do who knows how many hours at $120ph!
What I have done in those cases is authorize only a tear down and inspect for quote. Most of the dealers in this end of the world are not authorized to work on those pumps so in many cases all they can do is sell you a reman.
This week I had a guy from komatsu come out and look at the problem and test the pressures. He found that the auxiliary hydraulic foot pedal was malfunctioning trying to pump oil all the time. He shut off the hoses to the foot pedal and it seemed to have fixed the problem,. Today I used the machine for 3 hours and outside the temperature was 33C and the machines coolant temperature held steady at 70C, about 10deg cooler than normal. Not sure if it is fixed because it isn't heating up as much or if it was auxiliary hydraulics throwing the machine off? But apart from on one brief occasion during the 3 hours it worked really well and seems to run a lot smoother than before, possibly because he did adjust the pressure settings. So hopefully it keeps running well and I can get some use out of the machine. Thanks everyone for your help.
If the machine works, it's fixed. Thanks for sharing what was found. I hadn't thought of the pedal before.
I have the same problem in the same hole؟
I want your help ?
Where is the hydraulic auxiliary foot pedal