Hydraulic pump problem

a pressure gauge should tell you , could your system be dead heading and causing it to blow out something the system? what did you find wrong with it when you had trouble before?

the valve control body there was a guy who just found a loose screw in a joystick valve ,his problem was a slow movement but the idea of the problem is the same a restriction of flow  . search on this site you should be able to find it.

I’m no hydraulic mechanic by any means but the only logical answer I can think of is a blown rear seal on the pump. How else could the fluid get into the engine?  If it were me I would take the pump back apart, check for runout at the rear of the shaft (maybe a bad bushing or bearing) and look for wear on the shaft where the seal sits. If everything checks out put a new seal in and reinstall it and put a gauge inline to look for a dead head situation. Check it immediately after starting the engine. I’d like to hear from Bob Rooks or someone else who actually knows their way around hydraulic systems but that’s where I would start.

Sounds like there is something that’s keeping the relief valve from functioning, or it is set too high, assuming the pump is in proper working order. Yes, a blown seal is the only way hydraulic oil gets into the engine. A pressure gauge will tell the story.

Have you ever cleaned the valve? How is your return filter?