John Deere 500c hydraulics

[chrisdvorak]

I have a John Deere 500c backhoe that suddenly lost hyd pressure while digging, no noises or leaks everything just got very slow and sluggish, steering, trans, and brakes still work ok. I parked the machine to change hyd filters and when i drained the rear end found some metal that I couldn't identify. Could be the problem or completely unrelated. No foam in hyd fluid like if pump was cavitating. Could a bad de stroke valve on the pump cause this? Any input would be appreciated

- thanks

 

[Tx Jim]

Pieces resembling wire are broken spring. Check frt hyd pump drive coupler to be sure pump shaft turns when engine is running. Yes faulty stroke control valve could be the problem.

 

[chrisdvorak]

thanks, I will check the pump drive coupler. whats the best way to test the stroke control valve? I guess there is no way to tell where that spring came from but it sure would be nice to know...

 

[Tx Jim]

You could install a gauge and check pressure which I think should 2250 psi or possibly a little more.

 

[chrisdvorak]

Thats what i was thinking also but wouldn't that just test the pump? any way to isolate the destroke valve itself? or is it just something that you replace?

 

[Tx Jim]

Please clarify are you desiring to isolate the stroke control valve or destroking screw? What are you attempting to accomplish when you state "isolate"?

 

[chrisdvorak]

I am trying to test the electronic destroke solonoid on top of the pump, but was not sure on how to test a bad or stuck destroke valve

 

[chrisdvorak]

the coupler from the engine to the front pump checks out fine. also had machine running for about 20 min and could not isolate any hot spots that would indicate internal leakage. I should add that when you use a hydraulic function there is no change in engine sound, (usually bogs a little at idle) which makes me think that no fluid or very little is getting to the valve body. so my next question, were is the stroke control valve located on the pump? and anything to watch out for when removing the valve for cleaning? I don't want to mess up the pumps pressure settings.
-thanks

 

[chrisdvorak]

I cleaned the stroke control valve, there was some junk in it but did not solve the problem I have heard there is a priority valve somewhere on the trans that when clogged will cause my issue, can anyone shed any light on where that valve is located?
- thanks

 

[Tx Jim]

Priority valve on RH side of tran is designed to give steering priority oil but has no affect on whether frt hyd pumps oil or not. Maybe they were referring to the hyd filter relief valve.