4020 hydraulic problems

70DS · Apr 30, 2012

My new 4020 has some hydraulic issues. The steering and brakes work good, but the remotes are very slow and will barely lift anything. First I checked the priority valve to see if it was stuck, but it was moving fine. Then we pulled the stroke control valve, which was stuck. We freed it up and thought that we had found the problem. Once we cleaned it out and got it free it lost all hydraulic function. Had absolutely nothing. The transmission screen is clean and the filter is new. The transmission pump is pumping. So after that we pulled the hydraulic pump out and put a used one out of his parts 7520 in it. When we started it up it sounded better right off the bat. It made the usual new generation pump noises. It steered nice and everything. So then it went to the swather. It still won't raise it. It will barely operate the endgate on the baler. Does anyone have any ideas to what may be my problem. I am thinking there may be a leak somewhere in the steering or brake system that is taking the pressure away from the remote system. I am about to pull my hair out with this thing. I am sure it will be some simple little problem once I find it. Any body else ever had any gremlins in their hydraulic system?

Thanks
Clayton

Roger in Iowa · Apr 30, 2012

What was the pressure at a SCV?

buickanddeere · Apr 30, 2012

Installing a larger pump is not the preferred method to deal with leaks. Early or late 4020? PS or synchro? Has anybody tested pressure and flow of the trans hydraulics or just started throwing parts at it ?

70DS · Apr 30, 2012

The old pump was leaking so it was going to have to be dealt with anyway. So I didn"t really consider it just throwing parts at it. A 7520 has the exact same pump as a 4020. It had 2200 pounds at the remote last time we checked it. I am going to check it again next chance I get to work on it. I was just looking for some ideas. It is a 64 model with a syncro.

70DS · Apr 30, 2012

The old pump was leaking so it was going to have to be dealt with anyway. So I didn"t really consider it just throwing parts at it. A 7520 has the exact same pump as a 4020. It had 2200 pounds at the remote last time we checked it. I am going to check it again next chance I get to work on it. I was just looking for some ideas. It is a 64 model with a syncro.

4020guy · May 1, 2012

Pretty sure the 7520 pump is 4 cubic inch per revolution and a 4020 is 3 cu.in. or 30 percent more volume.....Ron

Tx Jim · May 1, 2012

(quoted from post at 01:36:34 05/01/12) Pretty sure the 7520 pump is 4 cubic inch per revolution and a 4020 is 3 cu.in. or 30 percent more volume.....Ron

AR101807 is the hyd pump that's substituted by JD for original hyd pump in both 4020 & 7520. R27150 PISTONs were used in both the 4020 & 7520 original pumps according the the parts catalogs.

Tx Jim · May 1, 2012

I also recommend checking stand-by pressure. If psi is 2250-2350 then I'd suspect faulty adjusted poppet valves in the SCV control valve housing. The rockers(parts key #13) & rollers(parts key #24) have been known to wear and alter valve adjustment.

Tx Jim · May 1, 2012

(quoted from post at 14:59:27 04/30/12) Installing a larger pump is not the preferred method to deal with leaks.

May I ask what leak you may think 70DS tractor has??

70DS · May 1, 2012

It had 2200 psi before we started fighting with it. I plan to get a guage on it the next chance I get to work on it. It acts bad on both remote circuits as well.

buickanddeere · May 1, 2012

Internal high pressure.

Tx Jim · May 1, 2012

(quoted from post at 18:26:27 05/01/12) Internal high pressure.

Internal high pressure leak is very,very difficult to diagnose with the very limited information given. BTDT first hand many,many times.

buickanddeere · May 1, 2012

Txjim you are correct.
According to CTM7.
The 4020 used either the 50cm or 65cm pumps with
30.2 and 39.5gpm capacity at 2300psi and 2500rpm.
The 7020/7520 only used the 50cm pump.
There is a 3000 series double body pump that pumps
106.4 gpm at 2800rpm.

Tx Jim · May 2, 2012

(quoted from post at 22:37:29 05/01/12) Txjim you are correct.
According to CTM7.
The 4020 used either the 50cm or 65cm pumps with
30.2 and 39.5gpm capacity at 2300psi and 2500rpm.
The 7020/7520 only used the 50cm pump.
There is a 3000 series double body pump that pumps
106.4 gpm at 2800rpm.

Research of the JD 4020 parts catalogs reveals that the 65cm(4 IN.3)) pumps were utilized in PFWD tractors only.

May I ask what 3000 series tractor utilized the double body pumps?

tim s · May 2, 2012

It was an optional pump for industrial loaders/back hoes. it is 2 pumps in one..

Tx Jim · May 2, 2012

Thanks Tim. I suspected it was an industrial model of which I have very limited experience as dealer I worked for was ag. only.

buickanddeere · May 2, 2012

My apologizes for being hasty and not providing a clearer
description. Deere at the time manufactured a series of
closed center piston pumps known as the 1000,2000 and
3000.

Tx Jim · May 2, 2012

Glen
No problem. We're all human and we all make mistakes. Have a good day.
Jim

70DS · May 2, 2012

I got to investigating the 4020 a little bit more tonight. The donor pumps compensating valve was turned out. I adjusted it in and set the lock nut and woo hoo the hydraulics start to behave better. So I went out and hooked it to my baler and it works the baler properly now. So I go over to my swather. Hook up to it and same old crap. It will only lift one side. It does lift the one side considerably faster. So I pulled the rephasing cylinder off of my parts swather that I just got. Put it on my good swather and it goes up and down now. The freaking cylinder had managed to blow out and was letting the oil straight through instead of lifting it. I am still going to put a gauge on it and check it one of these days. My buddy has a gauge I just didn't have it at the farm tonight while I was messing with it. At least I can swath my hay now since it is about ready to go. I did find out that the previous owner had a brake failure last summer and he ran it till it bypassed and sucked the pump full of brake debris. So I believe that is what started all the crap it was doing. Plus the old pump was a bit of a leaker. So hopefully it has worked out in the end.

Tx Jim · May 3, 2012

I'll recommend checking hyd pump stand-by psi very quickly. If you happened to adjust it too high you'll liable to blow seals in a hyd component such as the steering valve(no fun to repair)

4020 hydraulic problems

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