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  1. #11
    Bronze Member
    Join Date
    Dec 2010
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    60
    Tractor
    John DeereX748

    Default Re: blew out 4020 hyd pump.

    Friends father lost the piece today.

    Shop manager wanted to see it at the local dealer. Like I say it was 1/8 diameter about 3/16 long maybe the sides were round and both ends were the only parts rough and uneven. You could see a slight taper perhaps. This piece clearly did not come out of the front pump.

    It was black and appeared to be hardened.

    Pump went back together today. Not putting it back in though. Looking for a 4.0 to replace the 3.0

    Radiator was not completely blown. Had to close off two lines but the guy thought it would be repairable.

    We suspect there might be problems in the back pump and ran the front pump dry without warning. We get the front back together and take a peak in the back.

    Plan on starting the tractor when the engine is back together and do a capacity test for the back pump first.

  2. #12
    Bronze Member
    Join Date
    Dec 2010
    Posts
    60
    Tractor
    John DeereX748

    Default Re: blew out 4020 hyd pump.

    Havent pulled the rear filter yet. I replaced it two years ago and havent driven the tractor that much. Dip stick oil looks clean but we've focused on the front end.

    The fishnet filter was replaced two years ago. That helped a lot. I think it was collapsing when the oil got warm in the summer.

  3. #13
    Elite Member Tx Jim's Avatar
    Join Date
    Jan 2007
    Posts
    4,854
    Location
    North Texas
    Tractor
    JD 4255/Kubota M7040 HDC

    Default Re: blew out 4020 hyd pump.

    Quote Originally Posted by captplaid View Post
    The fishnet filter was replaced two years ago. That helped a lot. I think it was collapsing when the oil got warm in the summer.
    Cold oil will be thicker than warm oil. Is the "fishnet filter" you refer to the trans sump screen or the main hyd pump inlet screen? Before trans R&R I would disconnect line in frt of hyd filter crank tractor with a g gal bucket under it as see how long it takes to fill bucket. It should fill in 60 secs or a little less.

  4. #14
    Bronze Member
    Join Date
    Dec 2010
    Posts
    60
    Tractor
    John DeereX748

    Default Re: blew out 4020 hyd pump.

    We got it back together today. The pump didn't look like a thing was wrong with it. No scoring to scratches, no dings. It was a 3.0 c.i. pump. We put in a 4.0 c.i. pump and didn't return a core.

    Now we troubleshoot the backend.

    Yes, the pump was screaming like it was dry to the bone. The pump locked up and blew out the coupler.

    We tore apart the hydraulic filter. We found a couple brass flakes. Just a couple and more dirty in there than we expected to see.

    This tractor has been abused in it's life. This 4020 is on it's third front axle 1 fender replaced and the hood replaced once. The loader is not sprung but the cutting edge has been replaced twice and the bottom of the bucket once. This thing hasnt seen an easy life and maintenance was less frequent in Dad's later years.

  5. #15
    Super Member
    Join Date
    Feb 2008
    Posts
    9,393
    Location
    somewhere usa
    Tractor
    Deere 110tlb, 4520, x749, L130

    Default Re: blew out 4020 hyd pump.

    When you replaced the pump did you wind up with a new screen on the pump inlet?

    I ask because there is no way the small piece of steel could pass through the screen without destroying it.

  6. #16
    Platinum Member
    Join Date
    Apr 2011
    Posts
    738
    Tractor
    cx70,5510,4630,5005

    Default Re: blew out 4020 hyd pump.

    if you want to fix the 4020 front end permanently then put a 4630 front end under it.it sure sounds like a coupler problem ,it makes a lot of racket before it goes.

  7. #17
    Bronze Member
    Join Date
    Dec 2010
    Posts
    60
    Tractor
    John DeereX748

    Default

    Pulled the screen filter and it looks fine.
    I suspect the piece might have been floating around in the front reservoir sincebefore the screen filter was replaced three years ago.

    The pressure regulator in the dash was replaced about 8 years ago when the pump was rebuilt. We found problems with the valve to the differential lock and suspected then that something was floating around in the system.

    The front reservoir is clean. The screen filter in the sump is good.

    Probably rebuild the steering valve. Aside from the differential lock, we suspect the most blowby is from the steering and it is weaker than it should be. The hyd pressure flucuates a lot but is much bett with the steering lines plugged it is mucu better.

    The steering tracks straight enough so we think neither of the cylinders in the front are bad.


    As far as the root cause, my best giess is there was metal in the front reservoir that has been there for a long time.

  8. #18
    Bronze Member
    Join Date
    Dec 2010
    Posts
    60
    Tractor
    John DeereX748

    Default

    Had the jd mech rebuild the steering valve. He found 2missing o rings. Worn away.

    It was bypassing a lot of oil.

    This should help hyd pressure.

  9. #19
    Elite Member
    Join Date
    Mar 2002
    Posts
    2,829
    Location
    Iuka Mississippi USA
    Tractor
    3550 Fard Backhoe and a 1948 Farmall Cub,

    Default Re: blew out 4020 hyd pump.

    Is it an OilGear pump? I mnot super familiar with JD tractors but we do run JD scrapers with 4 CI OIlgear pumps. We had a few issues with a piston plug blowing out. I worked a job with a sheepsfoot tractor I cant remember the model but the pump blew out on it once and it was a steering priority valve. Its been 10 years ago I think the steering wheel deadheaded or something. The tractor did stall out it was idline but the operator restarted it and gassed on it to overcome the binding. It had a a 3 ci Oil Gear in it. A co worker had a 4ci on a wrecked cotton picker we put on it after the valve was re;paired.

  10. #20
    Elite Member Tx Jim's Avatar
    Join Date
    Jan 2007
    Posts
    4,854
    Location
    North Texas
    Tractor
    JD 4255/Kubota M7040 HDC

    Default Re: blew out 4020 hyd pump.

    Taylortractornut
    To my knowledge older JD scrapers used only piston pumps to build high pressures not gear pumps. I know all 4020's had piston pumps.

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