4020 hydraulic problem with loader

Roger in Iowa · Mar 14, 2013

Posted earlier about 4020 with dash controled SCV feeding loader valve where loader wanted to do the opposite of what you wanted to do, i.e. go to raise and loader wanted to lower first and the opposite if you wanted to lower it would raise.

New 3 spool valve closed center is now installed with supply coming off of fitting above brake pedals and return to rear of filter, like has been posted recently.

Now if you feather valve it will raise loader fully at about 1500 psi at a gauge plumbed into a SCV with dash lever held to activate. Lowering the loader almost falls and pressure at SCV is 500. You cannot lower loader and try to lift front wheels as pressure is only about 500 psi.

Standby pressure at SCV is 1900 and cannot be adjusted higher with set screw on bottom of main pump.

Acts like there is not enough flow from main pump or priority valve is malfunctioning? Just at a loss what to do. Do not know when filter or screen was replaced/cleaned.

David G · Mar 14, 2013

Define 3 spool valve?

Tx Jim · Mar 15, 2013

(quoted from post at 21:52:07 03/14/13) Define 3 spool valve?

A 3 spool valve has 3 spools and is designed to control the boom,bucket & grapple on a frt end loader.

Tx Jim · Mar 15, 2013

Without being there to diagnose the hyd's my first thought is faulty hyd 3 spool valve. Is the new hyd 3 spool valve one of the convertible types(open to closed/vice-verse)?? 4020 hyd psi should remain relatively the same whether raising or lowering the boom. With return hose disconnected from tractor(aimed in hyd oil filler hole) all levers on 3 spool valve in neutral and engine running does any oil flow out hose?? Hyd pump "if getting good flow from trans pump" has either some faulty inlet/outlet valves or stroke control valve to only attain 1900 psi stand-by pressure.

David G · Mar 15, 2013

Thanks Jim

Roger in Iowa · Mar 15, 2013

Both the original three spool valve and the new one are/were convertible. Problem occurred with the old valve too.

I am thinking there is something wrong with the tractor side of things.

Would a clogged or partially clogged filter or screen do something like this. Why would you have to feather the valve it it work okay, except for down. When moved to full stroke of valve the hydraulics DIE. Like something is telling the front pump not to pump at all.

When at 1900 standby the front pump does go quiet.

Thanks for any input/help. Will remove return hose and check for flow, but do not believe there is any as front pump goes quiet.

Tx Jim · Mar 15, 2013

(quoted from post at 09:04:21 03/15/13) Both the original three spool valve and the new one are/were convertible. Problem occurred with the old valve too..

Removing the return hose as I previously outlined will establish if valve has closed center plug installed correctly. Have you thought about plumbing loader valve into another tractor with closed center hyd's to determine if hyd problem persists??

Roger in Iowa · Mar 15, 2013

No. Unfortunately hind site is 20/20. Harder to do now since plumbing is hard wired so to speak.

Thanks.

DaveH IA · Mar 15, 2013

(quoted from post at 18:50:58 03/14/13) Posted earlier about 4020 with dash controled SCV feeding loader valve where loader wanted to do the opposite of what you wanted to do, i.e. go to raise and loader wanted to lower first and the opposite if you wanted to lower it would raise.

New 3 spool valve closed center is now installed with supply coming off of fitting above brake pedals and return to rear of filter, like has been posted recently.

Now if you feather valve it will raise loader fully at about 1500 psi at a gauge plumbed into a SCV with dash lever held to activate. Lowering the loader almost falls and pressure at SCV is 500. You cannot lower loader and try to lift front wheels as pressure is only about 500 psi.

Standby pressure at SCV is 1900 and cannot be adjusted higher with set screw on bottom of main pump.

Acts like there is not enough flow from main pump or priority valve is malfunctioning? Just at a loss what to do. Do not know when filter or screen was replaced/cleaned.

"Standby pressure at SCV is 1900 and cannot be adjusted higher with set screw on bottom of main pump".----stroke control valve is bad you need 2250# check filter and screen first

David G · Mar 15, 2013

I think the first issue would have been corrected by just sapping the hydraulic hoses.

I am thinking that there is an issue in the valve.

David G · Mar 15, 2013

swapping

belaw · Mar 15, 2013

(quoted from post at 04:06:59 03/15/13) With return hose disconnected from tractor(aimed in hyd oil filler hole) all levers on 3 spool valve in neutral and engine running does any oil flow out hose?? .

Minor hijack, but does flow from the return line indicate an open center valve?

Roger in Iowa · Mar 15, 2013

No problem on the high jack. A true closed center valve will not have any flow in the return to sump line when no functions are being used.

An open center system has flow all the time and is interrupted during use, except for oil returning from the other side of a cylinder/or motor.

Anonymous-0 · Mar 15, 2013

I had a loader doing odd things almost like you describe and found out that one lift cylinder was blown out internally. Oil would bypass through and apply pressure to the wrong side of the opposite cylinder.

nylon4020 · Mar 17, 2013

I had a similar thing as another fellow posted with a Farmall 460 and a schwartz loader. The a packing was blown in the lift cylinder and was bypassing to push on other side reversing action and very eratic. If both lift and dump are doing it and is new to the joystick...then looks like joystick or plumbing.

nylon4020 · Mar 17, 2013

Forgot to ask but is pump running all the time or when it shouldn't be and any lines warm?

I don't know enough about pressures and what should be where and when and where it goes to comment usefully. The lift cylinder packings fight each other between two cylinders and light pressure can allow the thing to work while full pressure can blow through a weak or bad spot in packer. A repack isn't bad but is time consuming and tricky solo as the cylinders are heavy and long. Just my two cents.

It sounds like it was doing it while running through both the SCV and the joy? I also was not able to apply enough down pressure to lift the front wheels at the time. That being said my 4020 and the 460 farmall...ones open the other is closed.

DaveH IA · Mar 17, 2013

You my have loader or valve problems -- but you do have tractor problems-----1900 # stand-by pressure----you need 2250--the priorty valve closes at 1800# to protect steering and brakes--- sounds to me like the stroke control valve or( pressure control valve)-- in the pump is bad and not building pressure--- you said you can not increase pressure with the adjusting screw ---- plug off the loader valve and check standby pressure --lift 3 pt and steer at the same time--

4020 hydraulic problem with loader

Roger in Iowa

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