1985 Liebherr 924 Excavator Losing power

Case450

Member
Yesterda it took me 8 hours to dig a trench 6 feet deep, 4 feet wide, 300 feet long. A 27 ton shovel shouldn"t take that long.
I have lost 99% of all power to right track.
As of today, I cannot swing left or right with a full bucket.

Pump dying or what? I am not an excavator guy so I"m not sure whats going on. It"s electric over hydraulic.
 
I'm going to assume that your machine has two pumps like most other excavators. That said, the pumps are set up to where one powers one track and a couple of functions, and the other powers the other track and the remaining functions.

Too they are usually designed where the two pumps tie together if you are traveling and using another function at the same time. One name for the valve that does that is the 'straight travel valve'. Basically it combines the pump flows so the one that would otherwise be carrying a track and the other function being used doesn't cause that track to lose flow and slow down, in turn causing the machine to walk to one side -vs- straight.

That said, try this test. Get your machine walking where you notice the weak track. Then hit another function (boom up usually works good because you can keep the lever pulled and not hurt anything). If you've got one pump section going bad then you should see the weak track gain power when the two pump flows combine. Given that you also have a problem with the swing, you could also walk the machine and swing at the same time. You should experience basically the same results doing this test, meaning the 'dead' track should see an increase in power, and you should have more power in the swing also. In either case you should see the increase in power with the combined flows, although you will probably also see a decrease in the speed of the functions due to the one pump handling the majority of the flow required......assuming that the problem is a bad pump.

I know for a fact this will work to test a bad pump because I used the same, basic, ploy to get a machine walked nearly a mile out of a pipeline right of way when one pump section went bad. Boom up, and hold the stick in that position to combine flows and keep them combined, and walked it right out with both tracks pulling.



I have tested, and had quite a few excavator pumps over the years so I have seen the problem your having along with quite a few others. As complicated and drawn out as it all sounds when I try to explain what to do, short of having a flow meter with the ability to put a load on the pumps this is about the only way I know to test a theory of a bad pump.

Hope this helps, and feel free to post again if you have any questions.
 
I doubt very much if the hydraulic pump has failed,if it has and you kept using it the whole system will be contaminated with metal fragments,valves cylinders and motors,if you suspect the pump pull the main hydraulic filter and the suction filter,examine them,if there is no lumps of metal in them put them back, have a good look at the switches on the dash,that machine if its a Litronic has several modes,if for example if its in heavy lift the flow from one section of the pump is dumped,the machine slows up etc to make more use of engine power,extra pressure is put on the main regulator valve and the machine will lift more(I take the engine is running properly)see what lights are on the dash,check to see none of the multiplugs are out or fuses blown,the next thing that could be wrong is the main regulator valve is stuck open or has blow an o'ring on the body,check them couple of things and see how you make out.
AJ
 
Okay, I started her up day before last, and dug a bit of clay out of the bank, and it was right gutless.
I changed the fuel filters and tried again, same results with no change, gutless.
So my last lil test run after the new fuel filters installed I walked it a bit (right track spins when in the air but not under the weight of the machine) and when I moved the boom up or down or curled the bucket the machine (motor) bogged down slightly.

So I am thinking if that"s the case the pump must be starving for hydraulic oil right? So I am assuming there must be a mesh screen inside the hydraulic oil tank like my dozer and loader do, and I am assuming there must be some main hydraulic filters but I can"t seem to locate the hydraulic filters. At the bottom of the tank there is a huge hose that feeds into the pump, and from there several lines that feed several valve banks.

Since there is no apparent spin on filter, the filter must be inside the tank no? If it is (I am going to dunk my arm into the tank to find out after supper) and I manage to change it, whats to keep the contamination out of the pump? This is too simple to be complicated! lol
 
The filters are in the hydraulic tank,look on top of the tank you will see a round plate with a circle of bolts the suction filter is under that,in the same area there is a smaller round plate with two slotted lugs,under that is the hydraulic filter with a magnetic rod,you need to look at that, there will be a little metal residue but that's not a worry,but if you have metal filings it best to not run the engine till the cause is sorted, have look at the tank outlet on the outside,the tank has an on/off valve,the lever must be looking the direction of the pipe to the pump,check that,also check that the arm rests go down properly and any safety lever is functioning properly,has that machine the option for to change the lever functions,if it has see that it is in the proper position,what happened at the start of this trouble.
AJ
 
NCWayne, Please e-mail me at your convenience so I can discuss Detroit N65 injector issue. Thanks so much. BDBGTO
 

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