Brakes locking up when hot

[SmokeEater]

Hello all, I have a 508 cat skidder that the brakes tend to get grabby on once the machine gets hot- as does the winch when in freespool, generally only a summertime issue and goes away after the machine sits for a little while. Also anything off-idle will release the brakes. Radiator is clean- gets blowed out daily and steamed at the end of each job. Fluids are full and do not show any signs of contamination. Any diagnostics that I can do on my end are greatly appreciated as this gets aggravating trying to figure out.

Thanks again.

[mudfarmer]

Does it have the same air/hydraulic setup as the 518? Check out this post https://forestryforum.com/board/index.php?topic=50438.msg729025#msg729025 (thread is about NO brakes but one poster had similar dragging issue as you)

another from the same poster that thinks dragging brakes caught his skidder on fire... https://forestryforum.com/board/index.php?topic=106241.msg1655370#msg1655370


and a different poster with an air leak from the "treadle valve" causing the brakes to be always on I guess. https://forestryforum.com/board/index.php?topic=95807.msg1482786#msg1482786  Hope this helps somehow

[mudfarmer]

I've never worked on one of these but was thinking about it some more while picking blackberries... An air leak seems likely if what the other threads say is right about how the system works - it seems likely to me because of your statement that above idle it works again - does this sound right that whatever compressor would make more air as engine rpm increases? (engine driven compressor?)

[SmokeEater]

There's no air system on this machine at all.

[beenthere]

Welcome to the Forestry Forum. 

 Fluids are full and do not show any signs of contamination.

Not sure what "signs" you are seeing, but the problem does sound like contamination to me. 

Fluid and filter change, and the recommended CAT fluid (not a cheaper substitute) would be my suggestion. Also, getting a service manual or get the service tech involved the next step. 
Won't be cheap. 

[SmokeEater]

Welcome to the Forestry Forum.

Fluids are full and do not show any signs of contamination.

Not sure what "signs" you are seeing, but the problem does sound like contamination to me.

Fluid and filter change, and the recommended CAT fluid (not a cheaper substitute) would be my suggestion. Also, getting a service manual or get the service tech involved the next step.
Won't be cheap.

I've got the manual for it, I'll have to do some digging and see what I can find, I do know that my dad has ran rotella in the transmission ever since he has owned it (15+ years) so that could very well be the issue