I have an Allis Chalmers 816 backhoe that the hydraulic fluid foams after running 2/3 throttle for 15 minutes sitting still not using loader or backhoe. I have rebuilt the hydraulic pump, changed fluid and filter, cleaned screen and changed rubber hoses going from tank (frame rails) to pump. There aren't any leaks now and the hydraulics are powerful now until the oil foams up enough that they start to get weak. I'm kind of at a loss. The pump is a double pump, 15 gph and 25 gph with the loader using the 25 and then goes beyound to backhoe and backhoe is 15gph using the 25ghp when needed. The power steering also uses the hydraulic fluid and is weak and jerky, I kind of think it needs rebuild. Could the steering be causing the foaming? if its not leaking could it be causing the foaming internally. The other thing is it calls for 20 wt oil and I'm using 33 hydraulic fluid. Could that be causing the foaming? ANY help would be appreciated!!!!!!! Thanks Rob
Do the power steering have it's own pump? If so check the axle shaft seals on that, it could draw air in there.