JD 955 Compact Tractor lost all hydraulic power today

[Hoopcoachd]

1998 JD 955 Compact Tractor lost all hydraulic power today - bucket was up and tractor was moving forward, I stopped, readjusted bucket, pushed forward and...nothing. Front hydraulics, PTO, rear hydraulics and transmission - both forward and reverse - all gone. How likely is it that the hydraulic pump went and not the hydrostatic transmission? The past 2-3 weeks I was having a much more difficult time moving the bucket, finish mower and bush hog...very slow. Fluid was always normal. Any ideas?

 

[J_J]

Check out your hyd with a 3000 psi pressure gage . If the pump is getting fluid, it should be pumping, and there should be flow through all the valves in an open center system.

If you max out the cyl, as in fully rev on the joystick valve, the relief valve should activate, and the gage should read the relief pressure.

Check the hyd level, and look for the correct color of the fluid and if there are any air bubbles. The pump just may have lost the prime.

If you have no outside leaks, and if the pump is pumping, the fluid is going somewhere. The purpose of the valve is to re- route fluid to the cyl, and when the cyl meet enough resistance, the pressure will build up and you should see it on the gage, and the lift or curl should move..

If the pump shaft is sheared off, you will have no flow. Did a QD come off. Check them for flow.

 

[Hoopcoachd]

Don't have a 300psi gauge - fluid is creamy and looks like it has tiny bubbles, almost frothy. No leaks. Absolutely the pump was overworked - carrying a load of firewood and just decided to run the bush hog down the fence line...the more I read in the service manual the more I lean towards system relief valve being stuck open. Now what? Also - thanks for your thoughts, expertise and consideration. I've worked on a lot of cars and trucks but this is my 1st tractor - not good with hydraulics but it looks like I am going to learn quick!

 

[J_J]

Change out the fluid first and find the suction leak. Tighten the suction hose or replace.

 

[Hoopcoachd]

Thanks JJ - I am heading out to change fluid but I have one more question - service manual indicates it is likely the System Relief valve. JD manual gives a picture with an arrow BUT I can't locate the corresponding bolt head on my 955...any suggestions where to find the relief valve and how to "reset"??? Thanks again.

 

[J_J]

Which relief, as there are two reliefs on the tractor, One at the FEL valve and one at the 3pt.

If the FEL relief was stuck open, I think you would hear it. It is not designed to operate with the relief open for long periods as heat will increase.

If you remove the relief valve and inspect it and clean it, that may fix the problem. Normally you can tell something about the relief by the noise it is making when you max out the cyl or overload the hyd sys in any way.

Let us know what you find out.

 

[Hoopcoachd]

Thanks JJ - here's the problem...the System relief Valve is supposed to be on top, just beneath the seat...doesn't look anything like the picture in the JD Manual. It should have a hex cap that comes off like a bolt head but I find nothing. JD 955 Compact - where else do I look for the System Relief valve?????

I've got a neighbor that knows Hollands well enough and he may have time Monday to take a look with me. Thanks again for your thoughtful help and consideration - I'm learning about hydraulics the hard way! I teach HS physics so this will certainly help!!!

 

[wdchyd]

Change out the fluid first and find the suction leak. Tighten the suction hose or replace.

X 2 ......:thumbsup:

 

[The Haymaker]

Change out the fluid first and find the suction leak. Tighten the suction hose or replace.

THIS, my dad just went through this on the same machine. Wasted a month on wasted teardowns and parts before tightening a loose filter.

 

[tlbuser]

Thanks JJ - I am heading out to change fluid but I have one more question - service manual indicates it is likely the System Relief valve. JD manual gives a picture with an arrow BUT I can't locate the corresponding bolt head on my 955...any suggestions where to find the relief valve and how to "reset"??? Thanks again.

Take a look here http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet, according to this, the hydro assy. has 6 relief valves. There is a separate one on the PTO. Check closely on the hard lines running from the oil cooler assy. I had to repair a 955 with similar symptoms. They rubbed together and had a pinhole leak.