4020 Hydraulic Problem

My 1971 model 4020 J.D. loses power steering, power brakes,3 pt hitch and remote power within a few seconds of pushing the cluth in. After releasing the clutch it takes a while to regain power unless you throttle up. I was told this is caused by an internal high pressure hydralic leak. It makes it dangerous to load the tractor on my tilt top trailer. What do I do to fix this?

I have a fix for older tractors but it doesn't apply to your tractor. I think that your tractor has a check valve but its up high at the top of the front oil cooler/reservoir.

I'm not real sure about the most likely suspects, trouble is high pressure closed center hydraulic is a lot like electricity. A failure anywhere gets the same leak result. I'd dig into the remote valves, the three point valve, the brake valves, the differential lock valve, and the steering valve and I'd go ask my nearest friendly Deere dealer about 1970s vintage service bulletins that cover the problem. I know those service bulletins were printed, but they are missing from the collection I have though the topics are mentioned in the indices.

From my web page:
"In the collection of Service Bulletins that I have, T69-3 page 3 (which I don't have beyond the index reference), T70-10 page 3, and T71-1 page 3 have information on loss of hydraulics with the clutch pedal pushed in side console tractors, at least late 3020 and 4020. I don't have Service Bulletins after 1972 which may have more on these problems."

I think those service bulletins may have pointed at the most likely or most experienced failures.

Gerald J.

Have you tried changing the hydraulic filter? Pulled the suction screen located behind the filter cover ? That is where to start.

4020's have a charge pump back in the transmission that feeds hyd. oil to the main hyd. pump up front. The charge pump stops turning & delivering oil to the main pump when the clutch is pressed down. If your charge pump is worn out the main pump is probably always running a little short on oil, now when you step on the clutch the main pump runs out of oil almost immediately.

When you loose your hydraulics, remove the side cover next to the clutch to access the pto valve and feel the housing, hot is bad, leaking internally. I've seen a few that leak internally and cause alot of hydralic problems. But the only fix is to replace them. Also while tractor is running engage pto with tractor at pto rpm's and remove the cover under the flywheel housing and look at the pto bearing housing and see if it is pulsating, if it is you need to adjust the pto valve. chris

Not to barge in on this thread but our '72 4020 is equipped with the hydraulically activated PTO as well and I was curious of how it operates.

What pressure is fed to the PTO valve(and from where) and what pressure do the slave pistons for the PTO bearing receive from that valve when fully applied?

Also if that valve was leaking, where does the leaking/return oil go?? Back to trans. sump or into the function return oil circuit??


Thanks in advance

Glen

Glen
The hyd pto is supplied by trans. pump and pressure should be around 175 psi. If valve leaks oil runs down outside of clutch housing. If pistons leak that's on inside of clutch housing

4020 Syncro-Range? Think!

HTR,
If you're referring to Tx Jim's comment when you posted may I ask "what do you mean by {think}"? I was replying to Glen D Anderson's question about his tractor's pto !!!!!!!!! When I sold '72 4020 syncrorange trans tractors straght from Waterloo,Iowa they came equipped with a hyd actuated pto clutch.

Tx Jim

Tx Jim

I didn't intend to be rude with that post. I know you are one of the most knowledgeable posters on the board. I also know that the pto on the 69 up 4020 syncro-range is engaged by hydraulic pistons, but not by transmission pump pressure. When I said, think, I was referring to is what would happen to the PTO, when you pushed the traction clutch pedal down, and the transmission pump stopped turning.

Sorry, should have kept my mouth shut. I only had a minute, when I posted that less than thought out reply.

HTR
First off there are a lot of posters on here that know more than I do about farm equipment. Also I didn't think you were rude I was just curious as to what you meant. It's been since the late 80's since I was a JD service manager so I've forgotten a lot of what I knew. You have my curiosity up about what pressure powers the hyd pto on a late model 4020 as I thought it was trans pump pressure because I sure didn't remember it needing 2250 psi. I will call my JD dealer today.