Mitsubishi ms40-8 intermittent track problem

Hello all,
I recently bought an old Mitsubishi MS40-8, not in great condition, but working pretty good.
I have already had a mechanic take a look at it and replace what was necessary, some piston seals, engine oil, etc...not really major stuff.
however, when i started using it, i noticed that going up hill, the right track would not move unless the left track also moved. if both are used the machine moves pretty much straight.
the mechanic suggested that it might be the seals on the spool that transfer the oil down the centre of the machine, sorry i don't know the English term for that part. so we replaced the seals, and the situation has improved somewhat. at low engine speed the right track still won't move unless the left moves, at high engine speed it works much better, but still sometimes it will not move on it's own. when it works it has plenty of power, but when it doesn't it just goes dead, it rotates a few inches and i can hear a distinct clunck from somewhere. Also when it doesn't work, the engine is not affected at all. I am not an expert on excavators, it's my first one, but from reading around i get the feeling it might be related to the relieve valve, or somewhere else the hydraulic fluid can be diverted by some reason or another.
anyways, I hope somewhere out there there is somebody who can help me figuring this out, the mechanic seems to blame the age of the machine, but for the rest she works great, with plenty of speed and power.
thanks

It could be the piston in the manifold where you activate the pressure for the hydraulic engine that is the problem.
The part that is routing the pressure.
Is it the same in the other direction also?

Are you referring to the pressure relief valve? because I was also thinking it could be part of the problem. I took it out to inspect it, it seems like it doesn't spring back freely when i push on it. is there anyway to check what the actual valve is so as to get a replacement? I mean what dimensions are critical?
yes the problem happens in both direction, especially when the Hydraulic fluid gets hot after an hour or so of use.
thanks for the input

Good day globe
Suggest that you begin by basic trouble shooting often operatives do not have pressure testing instruments but checking at the main motor lines on the weak side is a good starting point - no pressure testing instrument go beneath and switch main hose lines left to right - have plugs at the ready as fluid will run from the tank. We have a complete testing document but many find this a bit on the heavy side.
Kind regards
Uffex

Hi there,
thanks for the reply. I don't mind heavy stuff at all, I have a bit of an engineering background, just I am not familiar with hydraulics, trying to figure out what is what on an old machine without any kind of schematics or manual is my kind of fun... today i took out what i believe are the pressure relief valves for the three pump lines, they were completely stuck open, i cleaned them out, put them back in, the machine run perfect for half an hour, I mean at just a little bit more than idling revs was performing better than yesterday at half throttle in all functions, moving around at half throttle i thought it was gonna pull a wheelie on me . However, after i pushed it a little bit hard through some heavy mud, the right traveling motor started pushing not as hard, and then not push at all. I checked the temperature of the motors( not the gearboxes, they were both cool), the left one was warm to the touch, the right one definitely hotter, but not extremely hot. the hydraulic oil gets hot, but i can touch every line , nothing seems extremely hot.
Anyway, I let everything cool down for an hour or so, then tried again. this time the machine was running exactly like yesterday, I mean everything works fine, not great, and the right motor struggles at times. I adjusted the pressure settings on the valves, going from low pressure and gradually increasing until both motors moved. I put the machine with the blade against the side of a hill and I increased both valve's pressures at the same rate. what i found was that while with higher pressure the left motor will actually stall the engine, the right one would go only so far and then stop moving without stalling the engine, only the revs would slightly go down. So I backed down the valve's pressures until they would both relief under load. while i can hear a pretty loud hiss (which I am guessing is the valve releasing) from the left valve bank, from the right one I can barely hear it. So, my personal conclusion is that either not enough pressure is reaching the right motor because maybe of the control valve not fully opening or internally leaking to tank, or there is some kind of internal leaking in the motor that doesn't allow it to push as hard as it should. But I am a complete newbie in this field and I am only going with my instincts on this. I will try your suggestion about switching the lines and let you know, even though I have to say all other functions connected to the right bank work very good.
thanks a lot and sorry for the long story, but i guess the more details I give out, the more somebody can help figure this out.

Well it appears that you are making adjustments without any pressure observations certainly it is not a method I would recommend, you could end up with a costly machine. I attach the trouble shooting procedure and I hope it helps if not get lucky.
Kind regards
Uffex

Ommited from the post - information on the Mitsubishi excavators is rather scarce, if you are prepared to post good photos of the MCV - track motors - pressure lines we can make better information for you.
KR
Uffex

Hi all,
thanks for all the replies and sorry for my late reply, we have been without internet for a while.
So here is the situation, I have switched the main lines at the pumps, left to right controls and vice versa: situation unchanged.
I have then switched the lines at the central spool, so basically left control valves activate right motor and vice versa: still no change.
So if my logic is right it must be something in the travel motor.
So I have taken out the gears from the planetary hub to see if the motor would spin without any load. the motor spins at times, but then it would stop responding only to start again after a while of moving the control lever back and forth.
so i took apart the motor from the pump side. everything looks nice and tight,only there is some kind of internal spool with very small holes that were stuck. I proceeded to unplug them with a good dose of carb cleaner. I reassembled everything, and the motor was spinning like a beauty, very responsive to the controls from creeping to full speed. so i reinstalled the gears, tried again, still worked fine for a while and then stopped.
the weird thing is that when it refuses to turn, there is no change in engine sound, and if i keep the lever pressed and touch the pipes near the motor I can feel the oil flowing from one of the big pipes to the small one. So at this point I can only find two possible culprits. either the internal relief valve becomes stuck open for some reason or the brake cylinder is not releasing.
the case drain line joins very quickly with the other side motor, and as far as I can tell there is no filter for it.
I will take the travel motor apart tomorrow and take some pictures and post them here.
the final drive is an HY-DASH E105. I tried looking for information on the net, but either I am not good at searching or simply there is no information available for this motor.
Thank you again for the replies and suggestions

Good day
Compliments on trouble shooting
Kind regards
Uffex

Thank you very much, it means a lot to me. Swapping the connections on the central spool was no walk in the park, but essential to figure this out.
Actually I have good news, I have solved the problem. After disassembling and putting back together the travel motor for at least ten times, I found out that the 3 little pins that push against the collar on the pump body were totally missing.I don't know the exact components an hydraulic motor should have, but i kept looking at the spring retained in the pump body and thinking: This is doing nothing, it's not possible. than i found a picture of a motor that looked similar to this one on the net, and I saw the little pins. Big Eureka time!
Not being able to find them anywhere around here, I bought 3 drill bits that fit snug in the little holes and I have cut them to size. Put everything back together and the machine works like a charm. the motor still feels a little weaker than the other at low revs, but with a little throttle it goes like a beauty. I am now wondering if I should use slightly longer pins ( I cut them so 1.5mm stick out of the holes), or If I have tightened the three bolts on the gear side too tight. Any thoughts about this?
Anyway, I am already very happy the machine is working again after months of asking mechanics and getting the same replies, It's old get a new one, or take your machine to the scrap yard and get a new one. three little pins and nobody could figure it out...

Hello all,
still having some trouble with this final drive.
it works great when i start the machine, but after 10 minutes of work, even if I am doing stationary work, the drive looses initial push. The hydraulic oil doesn't get hotter that 50 degrees Celsius. It will crawl if the other side is also pushing, and if I do use it for a while it doesn't get hotter than the other side, on both the pump and gear side. When I activate the lever and the motor doesn't turn, I can see the case drain line hose coming from the central spool vibrating, like there is pressure in it on and off, I am guessing from the relief valve in the motor.
Somebody told me that I should tighten the three main bolts on the gear side just enough so that I can still turn the drive by hand turning one of the three gears. Is that a correct procedure? It feels like those nuts are not tight at all when tightened that way so I have tightened them a little more.I guess the O-ring on the face seal should prevent the bolts from coming loose, still it would be nice to have a feedback on how to reassembly it properly.
I will take the sprocket off and tighten the bolts like I have been advised and see if that makes a difference, meanwhile if anybody has some ideas it would be greatly appreciated.
all the the best,
G

Good day G
In your thread you explain that the case drain vibrates when you drive the weak motor, if I am understanding you correctly that will most probably mean that the motor is damaged and by-passing pressure fluid. I would suggest remove the motor and split it down I believe what is wrong will be obvious.
Note be aware to have plugs the fluid will run when you break the hose lines.
Kind regards
Uffex

hi there,
thanks for replying so fast.
I have already taken apart the motor so many times while trying to figure out what the problem could be, that I have got the technique down to a t, I only loose a little oil every time. I guess I learned the hard way when i wasted about 5 liter of oil the first time around...
Here is all the components. the only obvious thing I could find is the pins in the main body which were totally missing.I replaced them and it has made a huge difference, but still the problem appears after 10 15 minutes. I will upload pictures of other parts that show signs of wear, maybe you can point me in the right direction.
If you zoom in you will see a little indentation in the inside rim, roughly at ten o'clock.
You can see something must have got stuck between the upper dome like feature and the plate above. Also you can see the chambers for the little pistons are quite scratched.

Also if you zoom in there are quite a few scratches at the bottom of the rotor where it contacts with the plate at the oil inlet.
As far as I can tell, these are the only parts showing signs of damage that can possibly affect performance.
Everything else I have thoroughly cleaned and inspected, as far as i can tell it should be ok.
I'm kind of suspecting that the scratches at the bottom of the rotor can let oil through, but I am definitely no expert on the subject.
thanks a lot

Good day G
There appears to be some scores in the cylinders although its not so easy to see from the photo's I suggest you take the motor to a repair shop and get it tested, the only other possibility is the central passage seal failure. You could switch the lines from one motor to the other to take the motor out of the equation as I can see you are not frightened of work.
Kind regards
Uffex

Hi,
the cylinders are definitely scored, even though at the touch they feel smooth and pistons feel very snug in them
the central passage seals have been already replaced. I think it would be very hard to switch the motor lines as they are solid pipes, not flexible connections. You think the cylinders could be the culprits?
unfortunately the general attitude here is not to repair but to replace the whole thing, that's why I decided to try and do everything by myself. the puzzling thing is that the motor works really great when I start working, and then suddenly not. Like I said, the oil doesn't even get so hot as to loose viscosity I think, ambient temperature here is 35 degrees C, the oil goes up to 50C max, can 15 degrees make such a difference?
thanks for the help

Hi G
Cannot explain the situation you describe but is it possible to switch the motors that way you can be absolutely sure it is the motor.
KR
Uffex

Is it possible changing the motors hoses on the hydraulic manifoild ore make some extension hoses.
I think uffex has an good idea with changing the lines to eliminate problem.

So,
this morning I replaced the main lines from pumps to distribution bank, I guess they were as old as the machine is.
I don't think that was the problem and I don't want to jinx it, but I worked all day and I didn't experience any problems, I had a lot of fun finally, after months of banging my head on this problem. But I have learned a great deal, so all in all I'm pretty happy.
Next step is to set up the relief valves properly...
Thanks a lot for the help and all the best

DISASTER!!!!
Today I was happily working along, when all of a sudden I heard a clunk coming from the motor and it stopped working. I immediately opened it up to inspect the damage, and I found all the ball bearing loose. Basically those 3 bolts have come loose and everything got out of alignment. Luckily the only real damage I found is to the 3 cam shafts, basically the gears pushed against the cir-clips which in turn broke off the ends of the splines where they are retained. I am going to try and make the grooves deeper with a cut off wheel on a dremel, hopefully that should do it. But now I really need to know how tight these bolts need to be, I am guessing now they have to be on there really tight otherwise they come loose.
Any indication form you experienced guys would be a great help, I trust you more than these monkeys with a wrench that call themselves mechanics...

Good day
Suggest you take a close look at the transmission establish make & model research rebuild information, Mitsubushi machines as the the best of my knowledge were adopted by Catterpillar so those guys that contribute on the forum may be able to help with that information.
Kind regards
Uffex