troubles with my skid steer

[tessiers]

I have a Thomas T-83 skid steer I am having hydraulic troubles with. The system is a direct coupling from engine to 2 individual hydrostatic pumps then a gear pump on the front which operates the bucket and auxiliary. Each hydrostatic pump controls a drive motor, 1 for each side. Gear pump supplies the 3 spool valve for the bucket. All 3 use the same hydraulic reservoir.

Symptoms are:

Drives strong going straight, bucket is strong lifting and tilting, auxiliary hydraulics are strong.

Problem is when I try to steer left or right or operate the bucket while driving it loses most if not all power. Engine does not die out or bog down but hydraulics lose power. If I fiddle with the levers it will steer and drive, however the bucket will not operate while it is driving.

I think my problem is 1 or both of the hydrostatic pumps, the left seams weaker than the right. Anyone who knows what they are doing have an opinion? I have a shop that will tear them down and look at them but no one seams to want to test them because of bench contamination. If I knew how I would test them, I have a 3000 psi test gauge but not much else specialized.

Any insight would be greatly appreciated.

Thanks
Jason

 

[J_J]

Have you checked the obvious, fluid level, filters, correct fluid, etc.

 

[tessiers]

good questions but yes, actually had oil and filters changed at a reputable shop, he is a heavy equipment mechanic but said he was out of his element with the skid steer, offered to work on it but warned me he was no expert. Indecently he has done this before for me with other farm equipment and done a great job.

 

[oldnslo]

Do the hydros produce full drive power while going straight? If yes I doubt the hydros are bad. It sounds more like some control issue. Not sure what type of controls are those hydros and how or why they would have any effect on the gear pump for lift / lower. Should be two completely separate systems.

If no, I would check into the connection between the engine and pump drives. is it slipping under load?

Do you have a hydraulic schematic for this skid steer?

 

[J_J]

I believe I would be using a hyd gage to watch the pressure when operating.

Like oldnslo said, the gear pump is probably piggybacked on the piston pump and if the engine is turning, then the gear pump is turning. Install a male QD in a tee in the IN port of the loader valve and you can watch what is happening with the hyd.

Are there any safety switched that stops the loader valve from working. Does your seat have any kind of lockout?

Some machines have pressure switches, and temp switches, etc

 

[tessiers]

Talked with my mechanic again today, he says pressures are good, he thinks there is a priority valve of some sort that is restricting fluid in the system, all 3 pumps draw from a single suction line. I told him to give it a couple of hours and see what he comes up with. I do have an operators manual with a schematic of the hydraulics, brought that to him today.

 

[tessiers]

Mechanic opened the hydraulic tank yesterday and found 1" of sludge in the bottom of it. It had plugged the new filter up tight, and ruined 12 gallons of hydraulic fluid in the process. Problem was it was starving for fluid when working at all. Less than 20 hrs on the new hydraulic fluid. Tank has 2 covers that bolt on to clean it I guess, neither one had a gasket on it so I think stuff was getting in around the cover plates. He cleaned the tank, flushed it with diesel, put in a couple of gallons of clean hydraulic fluid, circulated it through the system, cleaned the tank again, new filter and new fluid and it is a new machine. We also added a couple of cans of trans tune hydraulic supplement and cut gaskets for the cover plates and sealed them up tight. Hasn't run like this all the time I have had it. He said he has never seen a system contaminated to the extent mine was, the machine spent most of its life scraping manure on a farm so it doesn't surprise me. He let me pay for the supplies but wouldn't take any money for labor, said he should have checked it more thoroughly last time he changed the oil.

Thought you guys might like to hear the results.

 

[Leejohn]

That is great, if he's a beer drinker I sure would take him a case. If not a gift of something would mean alot to him.

 

[J_J]

Thanks for posting the solution to the problem. Perhaps some people will log that problem and will help them fix their system in the future.

That tar like substance has caused many problems and wasted money to people try to diagnose and fix their hyd system.

Here is an article about tar like substance.

Root Cause Analysis | Case Study: Hydraulic fluid degradation | Plant Services

Using Oil Analysis to Control Varnish and Sludge

 

[tessiers]

That's interesting JJ, I thought the sludge would be from outside stuff getting in. I was a little surprised it was as bad as it was, but it has spent almost its whole life in extremely dirty environment, never worked exceptionally hard but poor conditions. I know the original owner and he wasn't big on maintenance, so that was a major factor I am sure, he sold the farm to a friend of mine who never used the machine much, when I got it we did a basic fluid filter change and started to run it, problem got worse over the course of 20 or 30 hours so I am sure all that stuff had settled while setting and we stirred it up by moving and operating it. Good lesson learned. Father says a couple hundred bucks is cheaper than a college course.