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Discussion Forum

1960s JD 4020 Hydraulic Problems

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10-22-2011 12:08:40

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I have an early 60s JD 4020. I recently changed out the hydraulic pump (driven off of front of motor; bought rebuilt pump with warranty $1200!!) and everything worked just fine last weekend. Today, pump sounds like it may be cavitating a bit when under load (i.e. makes a grattling sound when under load). I can raise the front end loader but it goes up really slow, seems the pump isn't pressuring up enough. Hydraulic oil level is topped right up and brakes, transmission, steering etc. work fine, changed hydraulic oil filters (2 filters as its a power shift transmission) prior to starting up after changing out pump, no leaks to speak of; basically everything works good except the pump makes a noise when under load that I don't recall hearing last weekend and front end loader doesn't work properly (neither smooth nor quick) both raising and tilting the bucket. Thought perhaps it may be sucking air? There is a cooler which I believe ties into the suction side of the pump via a ~1.25" rubber hose, tightened clamps up and doesn't appear to be leaking however may be very slight leak on cooler itself but its been there every since I bought the tractor. Any other ideas?

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Tony s.

10-22-2011 19:48:31

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
Did you clean the screen in the sump?

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10-22-2011 18:55:42

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
It's probably the coupler between the hydraulic pump and the engine. Check it. The little plastic bushing will wear and begin to make noises.

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10-22-2011 18:39:09

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
What kind of loader, loader valves and how is it connected to the tractor's hydraulics? A failing loader control valve can cause such symptoms. The front pump is supplied with what ever oil the trans pump has left over. After the powershift and pto is taken care of. Internals leaks in either will cause grief. What serial number is the tractor?

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10-22-2011 18:06:38

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
I'd suggest investing in a 3000# pressure gauge and a length of hydraulic hose (can use a hose off a existing piece of equipment, if so desired); plug it into the breakaway coupler, operate the scv and and see if you have about 2250# of pressure.

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10-22-2011 14:51:25

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
on my 3020 there is a screen in the bottom of the transmission housing where the hydraulic charge pump picks up the hydraulic oil, there is a large hex nut cap that needs to be removed and then this screen will come out. It is long and maybe 1' in diameter that pulls out that hole. It may be restricting the oil. Have to drain trans and not much fun but might be worth a look. If you get on J D parts on the computer the screen is part #R53169 nylon or AR26375 steel. May not be helpful information but relates to my experience.

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10-22-2011 13:36:00

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 Re: 1960s JD 4020 Hydraulic Problems in reply to YesterdayRick, 10-22-2011 12:08:40  
Yay! This is my first time to be the first to say....GET A BOOK!!!!! Okay, now that that is done, a little to chew on while waiting for your new shop manual to arrive, by the way, the deere shop manual is much spendier than the IT manual, but the hydraulic section is also much better, worth the money I would say.

First off, your pump will not be sucking air, as there is no "suction" side of the closed center piston pump, it is supplied by pressurized oil from a transmission driven charge pump at between 50 and 130 PSI. Your front end loader will require more pressure to perform up to par than steering, brakes and such, so lack of performance will be more noticable, and the steering and brakes are protected by a priority valve, so if the pressure or flow is weak, it will all go to those circuits before accesory hydraulics (the loader).
It coud be your new pump is not adjusted correctly, there is a process for checking the stroke valve adjustment (in the handy book....) or you could have a valve problem in your loader, or many other things.
First thing to do is get a book, then check line pressure, then check your charge pump pressure and flow, establish that both pumps are working well, then check for leaks or problems in the system.


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10-22-2011 19:34:33

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 Re: 1960s JD 4020 Hydraulic Problems in reply to sixtyninegmc, 10-22-2011 13:36:00  
My neighbor had this exact problem. I went and tried it and everything worked fine after a few cycles. Then I said you try it. He got on and started it a 3010, cycled everything and then it started cavating again,and making these weird sounds. All the time he had his foot on the clutch. The charge pump doesn't turn with the clutch pushed down. Be sure you aren't using the loader much with the clutch pushed down. There is a can between the cooler and the pump on our 4040 to help this. you could put one on your 4020. This is not right if you have a power-shift. Vic

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