78 Ford Cl340 skid steer hydraulics weak when warm

[happyhigdons]

My skid steer seems to work well when first cranked as far as going forwards and backwards and turning. After 10 minutes or so after it warms up, the right drive motor seems to get weak and not pull the same as the left drive motor. It also sounds like I can hear fluid bypassing somewhere.
My bucket hydraulics seem to function fine. Where should I start in diagnosing what痴 wrong?

 

[happyhigdons]

As I致e been thinking about what could be wrong, one thought I have is that if a seal is blown, allowing fluid to bypass, that would cause the hydraulics to heat up. I notice after running the skid steer plowing snow that after 30 minutes or so it will start to run hot. That could be from the hydraulic fluid heating up, and the hydraulic cooler which is in front of the radiator could be giving off enough heat to cause the engine to run hot.
I reckon my first step will be to buy a infrared gun and find the hot spots. Perhaps that will show where the possible blown seals are.

 

[Dave M7040]

Heating up the fluid is more a function of fluid passing through the relief valve than through a leaking seal.
I am sorry but I do not know anything about skid steers

Dave M7040

 

[RNeumann]

To me this sounds like a worn out drive motor? or something on the one side. Fluid naturally heats as it moves around and gets used. Much like engine oil- when you start the engine cold the oil pressure is high. Then it settles a bit as things warm up. I too am no expert but your first post kinda says it all. Everything is fine when cold, then one part doesn’t work so well when it warms up. My guess is that one side/part is out of spec and needs R&R.

 

[happyhigdons]

I’ve rebuilt valves and cylinders, never been into a hydraulic motor or pump. Is it mainly replacing seals or? It’s old, so parts are a problem, but I have a place I can get just about any o ring and the nylon seals.

 

[oldnslo]

Most skid steers have piston pumps and some form of piston motor. These are all metal to metal sealing surfaces. Depending on what is worn you might be able to relap the mating parts but usually they require new components

I would suggest seeing if you can find a parts break down and then make a decision on how to proceed

 

[happyhigdons]

So to lap would one use something like a valve lapping compound?
Jeff

 

[oldnslo]

Yes you need lapping compound and flat surface

Note: you can only lap the parts if they have minor scoring and they must be thoroughly clean before being reassembled

That old of a unit might be beyond simple lapping of parts.

 

[happyhigdons]

Ok, I’ll have to give that a try. I found a manual online that I purchased. The loader pump appears to be a vane pump, but the drive pump is a variable placement piston pump. If I understand it correctly, the drive pump has two sections, one to each drive motor, and on the end of the pump is the vane pump for the loader. However, the loader is connected to the first section of the pump, the malfunctioning wheel motor is connected to the second section of the drive motor, and the second wheel motor is connected to the vane pump on the end of the motor where I would think the loader is supposed to be connected.
Looking at the pump from the return side of the pump. Right hand side is connected to the engine, first stage to loader, second stage to right drive motor, left hand end of the pump which I think is the vane pump end is connected to left drive motor.
I’m trying to get an understanding of how the hydraulics work before I pull it apart.

 

[happyhigdons]

The drive motors are both Char-Lynn 25 motors. The motor that is not performing properly has a lot of fluid leakage where the motor bolts to the skid steer. Anyone know where I can get a parts breakdown or more information on this motor? I did a google search but couldn’t come up with a Char-Lynn 25. It appears Eaton purchased Char-Lynn. This is a picture of the drive motor: