John Deere 2520 pump whining and no power steering

[Pauly2124]

Hello everyone! I am a really new poster but come here often for advice and help. I own a 2007 John Deere 2520 with 400 hours and I am having trouble with the power assist steering. When the tractor is running the charge pump is whining and the power steering does not work. I have changed the fluid and the filter. I have cleaned the screen. But is seems like the pump is not getting enough oil. I can turn the wheel really really slowly with one finger but when I try to drive it has no power assist at all. I have tried three different dealers but nobody seems to have any idea. Can anyone here help with how the charge pump gets it's oil? Thanks!

 

[DFB]

Well if it your tractor works at all similar to my JD4100 charge pump pressure is created by a needle/spring/shim assy in the valve block. And the diagnostic procedure would be to pressure test the charge pump at the block pressure port first to see if it was within spec and if that tested correctly any problem of internal hydraulic leakage would either be in the steering scu (selective control unit) or with the steering cylinder. The test to diagnose which of those two parts would possibly have an internal leakage is a fairly simple procedure. Seems a test a dealer could easily run. Is there any visible leakage or damage around the steering cylinder? IMO that unit would be most prone to wear or damage.

 

[Pauly2124]

Thanks for the reply. I will test the charge pump pressure tomorrow morning. It should be 283 psi at the block pressure port. I have read the procedure to test the steering valve and the steering cylinder. I will do those also but it really does not seem to be there. I can turn the wheel easily as long as I go really slowly. It seems like the pump is not getting fluid. The pressure test will tell me alot. Do you know if the charge pump gets oil directly from the sump after it goes through the screen? By the way the steering cylinder is not damaged and does not leak.

 

[DFB]

On mine works this way...

Spin on filter - charge pump - steering PCV - SCU - steering cylinder -
return flow - SCU - oil cooler - sump.

Spin on filter has been changed you say...where did u get the pressure test rating
my system pressure (charge pump) specs 995psi at full rpm and oil at operating temp

steering pressure relief valve is set at 260psi

You could dissemble and inspect both pcv asy and/or steering pcv
FYI PTO clutch and brake work off charge pump pressure too (lower pressure than steering 71psi)

Good luck

 

[Pauly2124]

I took the valve out next to the pressure line port on the side of the charge pump cleaned it then put it back together. Seems to be good now. I think it was stuck open and there was not enough pressure going to the steering valve. Thank you so much for your help.

 

[DFB]

Good job!

 

[Underapew]

Friends, I believe I am having the same issue. Can someone please tell me where on the tractor this valve for the charge pump is located. We've tried to find it, but I guess we are lost. Appreciate the responses in advance.