John Deere 500c hydraulics

[chrisdvorak]

that may be it, were is the hyd filter relief valve located?

 

[Tx Jim]

Correction: I was thinking about smaller tractor when I stated RH side. Hyf filter relief valve is on LH side on a 500 series. I don't remember which valve is filter relief but I think it's either key 14 or 25.

 

[chrisdvorak]

I've attached a pic of the valve housing the plug closest to the rear of the machine is plastic and has an electrical connector on it. I did not see that in the parts diagram, would that be the relief valve?

 

[Tx Jim]

As I previously stated I don't which valve is the valve in question. You need to acquire a JD service manual for your tractor.

 

[chrisdvorak]

here's an update of whats been done so far
-filters changed/suction screen cleaned
-all valves inspected in trans housing including filter relief (clean)
-control valve on pump inspected (found bits of what I assumed was cyl chrome in it, cleaned but did not improve problem)
-replaced screen in front pump (little dirty but not too bad)
-replaced O-rings on electronic destroke valve
today I had the machine running and while I manually destroked the pump (T screw on top) and engaged it again I could feel/hear the pump kick in for a second but it would not stay engaged.
the loader barely moves at all now, the backhoe functions but very slow and weak.
I don't have gauges to check pressures but I have a hard time believing that the pump would go bad in a matter of seconds with no warning?
I am thinking i'll pull the control side of the pump apart and inspect it. anything to watch out for when splitting it?

 

[chrisdvorak]

well ended up pulling off the control side of the pump and found a hole plugged with chrome chips which was the problem.

 

[Tx Jim]

Thanks for update. I think you need to attempt to determine where chrome chips are originating from.

 

[chrisdvorak]

the machine had been sitting for a few years and the dipper cylinder in particular had some rust spots and I think that's were the flakes are coming from. I have since sanded/polished the spots down, I don't know how the flakes are getting to the pump though? I would think they would wind up in the filters or screen first.

 

[chrisdvorak]

well all was good for awhile now same problem again. pulled control side off pump and small holes were filled with metal pieces again BUT there is no metal in filters or screen in pump? would this mean that the metal was coming from the pump itself? also I checked pump pressures at idle it goes right up to 2200 psi but when any function is activated it slowly drops to 1000 is this normal? charge pump is 85 psi standby and never dropped below 50.

 

[Tx Jim]

I think trans pump pressure should be in the 155 psi range. Frt pump should be 2250 psi and hold that pressure IE not drop to 1000 psi. I think it's possible metal flakes are originating from frt pump possibly the shaft brgs.