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4020 charge pump
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tonnahope
Posted 12/24/2009 10:01 (#983231)
Subject: 4020 charge pump


Owatonna MN
We have a 4020 sync with a 740 loader on it.  It has trouble losing hydraulic pressure when we are on the clutch a lot.  Has anyone heard of an auxillary pump, electric or otherwise that can be put on to keep the pressure up?
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rocknkcattleinc
Posted 12/24/2009 10:20 (#983262 - in reply to #983231)
Subject: Re: 4020 charge pump


NW Iowa
Thats a common problem, don't know of any extra pumps for them. We had deere rebuild the pump and that didn't help. Our pressure loss problem first started right after john deere put a new clutch in it. And i know they have a dry clutch which is weird. Sorry i couldn't be more help but i thought i'd put that out there to see i anybody could help both of us out.

Edited by rocknkcattleinc 12/24/2009 10:21
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amax
Posted 12/24/2009 10:26 (#983271 - in reply to #983262)
Subject: Re: 4020 charge pump


Vidalia ,Louisiana
Hi
If you have a manual trans the charge pumps stops everytime you push the clutch in.
Powershift should run all the time.

At least that is the way I remember it.

TIA

Amax
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rocknkcattleinc
Posted 12/24/2009 10:52 (#983316 - in reply to #983271)
Subject: Re: 4020 charge pump


NW Iowa
I loose pressure even when the clutch isn't in, just not as fast or as much on my 69 4020, but my 70 4020 don't loose any pressure with a big loader on it.
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Claymore
Posted 12/24/2009 11:33 (#983385 - in reply to #983271)
Subject: Re: 4020 charge pump


I have the same problem with my 4320. The Deere dealer says that I may have an internal hydraulic leak. Once the main pump is primed, it should keep going as long as oil is recirculated back to it. If fixing any internal leaks doesn't help, I wonder if an auxiliary charge pump could be run off of an orbit motor, or would that be like running a motor from a generator that is hooked to it? Perpetual motion doesn't work, but I don't think an auxiliary charge pump would take much power to run, as they don't make much pressure. The pump that takes the most power to run is the big closed center pump that is run off of the engine.
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Gerald J.
Posted 12/24/2009 12:05 (#983454 - in reply to #983231)
Subject: RE: 4020 charge pump CHECK VALVE



There is a JD service information on that for the early 4020 and like vintage new generation tractors. The biggest problem in these is a check valve deep in the transmission wears out and lets the front reservoir (oil cooler) drain back to the sump when the charge pump isn't running. I have the details from that service information on a web page. http://www.geraldj.networkiowa.com/4020si.htm

You can get that SI printed off at your Deere dealer, but now on the computer there's no pictures like there was on the microfiche I was able to gather data from. My sketches are rough.

My 4020 has worked find ever since I did the elbow mod (date on the parts ticket). I've been in an excavation, pushed the loader bucket into the wall, pushed in the clutch, lifted the bucket full of hard dirt while spinning the steering wheel (and the front wheels) lock to lock and in reverse and then let out the clutch and backed up. I've let it set over winter, pushed in the clutch and started it and lifted the loader several feet before letting out the clutch to back out of the shed.

Side console tractors, my collection of service bulletins says, don't have this check valve, so loss of pressure with the clutch pedal pushed has to come from a high pressure leak which can be anywhere on the pressure circuit since its held at high pressure all the time. Besides split pipes in the transmission housing, every valve is a suspect. I have hints of those SB on my web page, but I don't have those particular issues.

 Gerald J.

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Gerald J.
Posted 12/24/2009 12:10 (#983464 - in reply to #983385)
Subject: Re: 4020 charge pump



The JD service bulletin index I have says there's a high pressure leak in the side console tractors. Either a split pipe in the transmission at pressure, or a valve. Any valve, steering, brakes, remote, three point, or differential lock is suspect. And each could be contributing some leak.

There's several gallons of oil in the front reservoir (oil cooler) that should keep the pump supplied if no oil is returned to the sump unless you have large single acting cylinders or really big and long loader cylinders.

Adding another charge pump won't be permanent cure, high pressure leaks tend to wear bigger holes.

Check for a hot valve.

Gerald J.
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dondozer
Posted 12/27/2009 18:09 (#988733 - in reply to #983231)
Subject: Re: 4020 charge pump


NW Ohio,near Findlay
Agree with all the posts,also check wash out screen in trans sump. Oil must be drained, remove screen, and clean. This supplies the transmission pump first, then charges the hydro pump. Service manuals covers this, gives trans pump pressures to see if you have a problem here first.
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