e70 cat, one side works the other doesnt

[muddstopper]

Went to look at a e70 cat trackhoe today and didnt like what I found. Not sure the year model early 90 something. Serial number is 3cg10421 if anybody can look it up. I knew the machine was old, but was told it worked fine the last time it was used, about 2 years ago. Been setting ever since. Climbed in cab and machine fired right up, which was a pleasant surprise as I expected dead batteries. Fluid levels where good, oil looked clear. Let it warm up a bit and then tried to move some loose dirt. Root boom wouldnt hardly lift, bucket wouldnt curl and one track wouldnt travel. Dipper boom had plenty of power. You could raise the machine and drag the bucket buried to the top thru the dirt, you just couldnt roll the bucket and lift it off the ground, well you can, but its very slow and very weak. The swing seems to work pretty good. I didnt get the machine, but feel that what ever is wrong could be a minor fix, just need to know where to start looking before working on it. Owner doesnt have any of the operator manuals. I could really use a hyd schematic if anyone has one. I just opened the doors and did a visual of the valve bodies. One observation I had was that the relief in the middle of the valve bank looked like it was screwed all the way out. I am thinking sabotage by a fellow that used to operate the machine and was trying to buy it. If the relief is all thats wrong, then its a simple fix, but I aint willing to take the chance and dont want to buy the machine to find out instead of a adjustment, it could be a $3000 pump. I also dont want to fix the machine and have the other guy step in and buy it out from under me so, any work I do I have sneak around and do. Yea I know, it sounds like something to stay away from, but the owner is 86yr old, bad health, and just wants rid of the machine. I can use it and I feel the other guy is just trying to take advantage of a old man. So if anybody has a hyd schematic or knows where I can get one I would be very thankful.

 

[oldnslo]

Mudd
Did you notice if this machine had a single pump or multiple pumps feeding the valve stack? I am not familiar with this cat but know that some older case models used dual pumps and if one didn't work you lost those functions.

I did a search for Cat e70 hydraulic schematic and a couple of schematics came up that were kind of blurry. In trying to follow them it appeared like this is a dual pump system but not 100% sure that I was looking at the correct schematic for the serial number you have listed.

 

[muddstopper]

Well, best I can tell there is only one variable pump on the back of the engine. Theres a "But" there, from what I can tell there is supposed to be a pilot pump also. I found a schematic on line that suggests there are three pumps but I aint sure its the right schematic and its so small I cant read it. Tried printing it off and blowing it up and still cant make out the symbols. I plan on going back and taking a few tools when the original operator isnt around. My thoughts are if the guy sabotaged the machine by screwing out the relief, it wont take but a minute to find out. If its something else, well I'm not sure how far I want to get into it. When I go back, I'll open up the engine compartment and see whats in there.

 

[muddstopper]

I did a search for Cat e70 hydraulic schematic and a couple of schematics came up that were kind of blurry. In trying to follow them it appeared like this is a dual pump system but not 100% sure that I was looking at the correct schematic for the serial number you have listed.

Thats the same schematic I downloaded. Items 32,33,34 are pumps. 32 being a rear pump and 34 being a front pump. 33 is the pilot pump. I saw the pump on the rear of engine, but didnt look up front. I am having a hard time following the lines in the drawing to see which pump works the right side joystick and right side drive motor. If i could blow it up big enough, I could trace the lines, but I cant read that little print.

 

[oldnslo]

Mudd
If possible confirm that you have pilot pressure at both joysticks. From memory the front pump looked like it fed the right valve bank & the second pump fed the left valve bank. I do not recall which functions were on each valve bank though.

Good luck on getting this figured out.

 

[muddstopper]

to be honest, I have just about decided to not mess with it. It could turn into a money pit pretty fast. Altho, I still believe its nothing major like the main pump. As for the pilot pressure, not sure how I want to test individual joysticks. I will say the right joystick, the side that aint working, is awful easy to move, so pilot pressure could be low. One thing I have considered is just swapping the main pressure hoses at the pump, altho I havent looked to see how hard that might be to do. My reasoning is if the problems swapped from right side to left side, I would know the one pump isnt being energized and the problem wouldnt be pilot pressure at the joystick. If the problem didnt swap sides, well this should tell me the problem isnt the pump, which is the high dollar part. Now, if the problem is in pilot pressure to the right joystick, but the left side has pressure, I would just need to find where the pressure is split and see if that valve is stuck. The dang relief screw that looks screwed almost all the way out is just knawing at me. I think before I try anything else, I am going to count the turns and crank that screw in and see what happens. I havent been back to the machine since first looking at it.

 

[muddstopper]

found a little better schematic http://ww2.justanswer.com/uploads/DI/DIRTWRENCH/2014-03-19_233459_pilot_lines_e70b_schematic.pdf

 

[oldnslo]

In looking at the schematic you found they call out the different lines but I can see any readable numbers. #42 is the pilot pump so suspect that is the rear pump. Would suspect that if one side has pilot pressure the other should but who knows....

Also can't tell for sure but suspect the two variable volume pumps have some form of Horse power control possibly with load sense also. If one of the pumps is not getting a load sense signal it will not come on-line. Be nice if you had access to this for a couple days and could take some pictures of different components or if you have a good local Cat dealer will they provide a readable schematic.

Lots of questions but not very many answers...

 

[muddstopper]

Yea both schematics are hard to read. You can at least trace the lines on the second one. Best I can tell, (first schematic),pilot pressure goes from the pump to a filter #30 and then on to a proportional pressure reducing valve #19 and then a manifold #20. #22 is a pilot relief and for some reason there is a accumulator. #23. Going from memory, its the pilot relief or proportional valve I believe is screwed all the way out. Anyways, with the storm coming in, I probably wont go back to look until next week sometime. I am going to talk to the owner and see if we can work out some sort of deal before I start trying to fix the problem. I can donate a little labor, but I cant put parts on a machine I dont own or priced to high for me to buy.

If you look at the second schematic, it does identify things the first schematic doesnt, but you cant read it. I do believe you are correct that the front pump feeds the right side and the rear pump the left side.

 

[oldnslo]

Mudd,
In looking over the schematic I posted it appears that #19 the prop'l reducing valve ties into the pump control. Since one side is working I doubt this is the problem area. This could possibly be used as electronic HP control since the specs for the e70B state 53 HP mitsubishi engine, 34 GPM flow & system relief of 4,500 PSI.

Looks like items #11 are the main reliefs in the valve stacks. Since the show two one of them could be bad or misadjusted causing half of the system to be weak.

Item #9 (electronic Engine control) also appears connected to the pump control in some fashion. Again doubt this is the problem since one pump works.

I believe the pilot signal to the joysticks goes through item #15 Hydraulic activation control then feeds all the joysticks or foot controls. Based on that I doubt it is a pilot issue but possible a line is pinched or plugged. I suspect the accumulator is there as an emergency pilot supply to get the bucket on the ground if the diesel engine fails. NOTE: That is just an educated guess.

I found a couple of different posts about this same problem and none of the answers were the pump is bad. It was always a control issue. Big question is how to you diagnose which component on machine that isn't yours with tying up some serious time.

Also saw one post where it showed the main hydraulic pump model as A10VD. The A10V sounds like Rexroth model code but could not find anything A10VD.

Best of luck on your very tough decision of is this worth the trouble..