losing hydraulic function on 4020

[docgrt]

I have a console 4020 lp that all hydraulic functions quit if you mash the clutch for over a few seconds. What's up? Can be very dangerous at times with no brakes or steering.

 

[Anonymous-0]

Sounds like you have a high pressure leak to sump, after a cold start up you might be able to feel some of the hydralic components for heat. I'd look at the pto valve on the left side of the steering console. Svc's or rockshaft valve would be next in my book. chris

 

[buickanddeere]

iirc there is supposed to be a check valve that prevents oil flowing back from the charge side of the front pump back into the transmission.
Could be more than one problem with low or high pressure side leaks back to sump.
Anything been worked on or added to the tractor such as a loader ?

 

[Tx Jim]

(quoted from post at 12:34:41 10/22/13) iirc there is supposed to be a check valve that prevents oil flowing back from the charge side of the front pump back into the transmission. ?

b&d
Although the check valve you refer to is important ithe check valve isn't causing docgrt tractors problem.

 

[Tx Jim]

matthies
I agree with matthies on checking for a hot hyd component. How long since hyd filter was changed & sump screen cleaned?

 

[David G]

The clutch runs a hydraulic charge pump in the transmission. I would think you either have a bad leak or front pump is shot.

 

[Tx Jim]

(quoted from post at 13:20:50 10/22/13) The clutch runs a hydraulic charge pump in the transmission. I would think you either have a bad leak or front pump is shot.

Problem is more than likely lose of supply oil by depressing clutch pedal rather than a faulty frt pump.

 

[docgrt]

Been that way since I "ve had tractor. Just no getting around to addressing the problem

 

[docgrt]

Will ck that and get back to you

 

[Mr sl esq]

I have a 1972 4020 that that happened while using it one day. I had to run motor at almost full rpm. Turns out it was a broken steel pipe coming out of the charge pump in the tranny.

 

[Anonymous-0]

I have to agree with B&D. The check valve is a possibility, actually there is a series of 4 check valves in a housing. Had trouble with my console 4020 twice, would lose all hydraulics if I was on the clutch much at all, like backing a wagon in the shed. One time one of the check valves was stuck open by a piece of debris. Second time I found no obvious problem but I replaced the valve from trans pump. There is an upgraded check valve from Deere, it has a groove that an o-ring sets in for a better seal. It did the trick for me.

 

[David G]

Correct me if I am wrong, but doesn't the front pump have to suck through the transmission pump if the clutch is pushed in?

A pump that does not suck well would not work as well if the charge pump is not charging.

 

[buickanddeere]

Front pump does not "suck at all even if in brand new condition.It's a closed center variable displacement radial piston pump.
Safe to say many thousands of front pumps have been replaced on a wild a$$ guess. When the front pump was 100% functional and the problem was a faulty supply circuit.

 

[Tx Jim]

(quoted from post at 20:16:36 10/22/13) I have to agree with B&D. The check valve is a possibility, actually there is a series of 4 check valves in a housing. Had trouble with my console 4020 twice, would lose all hydraulics if I was on the clutch much at all, like backing a wagon in the shed..

The hyd check valve on JD tractors is designed to keep hyd oil from flowing back to sump when engine isn't running(nothing more-nothing less) When engine is running and trans pump is pumping as engineered the check valve will be OPEN not closed so therefore as I previously stated a "true check valve" isn't the problem. I don't know what valve you stated had debris in it but to my knowledge(memory) there's only one check valve. I think you are referring to the valve housing with the clutch & pto valves in it.

 

[Tx Jim]

(quoted from post at 00:43:22 10/23/13)
Safe to say many thousands of front pumps have been replaced on a wild a$$ guess. When the front pump was 100% functional and the problem was a faulty supply circuit.

I also agree with b&d that many frt pumps have unnecessarily been replaced from very poor to NO hyd diagnostics.

 

[8850dave]

What valve do I need to check or change on a console 4020 that is hard starting cause the hydraulics are trying to pump when starting, if turning steering wheel that releases some pressure.

 

[Anonymous-0]

The other 3 valves I referred to are probably more accurately relief valves, they return oil directly to the trans. Without digging out my tech manual I cant remember the exact functions of each one. But a small chunk of plastic that had fallen into the trans had somehow worked its way into one of the ports and held the valve open. One in a million chance I guess.

My tractor has over 9000 hrs on it and it does have some leakage in the PTO valve and SCVs. Probably the trans pump is a bit weak or leaking lines also. The upgraded check valve helped in my case. It was the easiest and cheapest repair, other than changing the filter and cleaning the screen.

I enjoy these discussions. I definitely learn more than I contribute.

 

[Tx Jim]

The check valve that is most often referred to is designed to stop hyd oil drain back when engine is stopped so that frt pump won't starve for oil on engine start-up causing 3 pt hitch to rattle on initial raising after engine starts

 

[Tx Jim]

(quoted from post at 07:16:59 10/23/13) What valve do I need to check or change on a console 4020 that is hard starting cause the hydraulics are trying to pump when starting, if turning steering wheel that releases some pressure.

Destroking screw is parts key #6 (AR33249) was offered as a kit but is now subbed to the following part numbers. These part numbers are correct for a hyd pump without a serial number plate.
A4365R O-Ring View/Update 0.87 USD
R26448 O-Ring View/Update 1.51 USD
R27171 Screw View/Update 7.67 USD
R27475 Fitting View/Update 5.43 USD
34H254 Spring Pin View/Update 0.33 USD
Parts that have an issue will display a flag. *Subtotal 15.81 USD

 

[David G]

Where does the front pump get oil from when clutch is pushed in?

 

[Tx Jim]

On syncro-range trans frt hyd oil reservoir until it's depleted or hyd function such as frt end loader that returns oil to the charge circuit.
On Powershift clutch pedal operation has no affect on frt pump supply oil

 

[David G]

So bottom line is that it must suck through the transmission pump once the front reservoir is depleted, or you will lose all hydraulics.

 

[tim s]

No, the front pump will not suck a drop, it must be pressure fed, or at least gravity fed,, return oil from different functions are routed to the front pump, this is one of the primary reasons for returning loader oil through the filter bowl, the loader return oil is going to the front oil while the clutch is depressed working the loader..

 

[David G]

OK, This has always baffled me, so bear with me.

How does the oil get from the sump to the front pump when the clutch is pushed in?

 

[Bob]

"How does the oil get from the sump to the front pump when the clutch is pushed in?"

It DOESN'T. (Synchro range)


The only oil available to the front pump while the clutch is depressed is the oil already in the oil cooler and reservoir AND "function return" oil.

 

[Larry in WNY]

Do you still have the part number for the check valve kit? We have the same problem on our 4020.

Larry

 

[Tx Jim]

(quoted from post at 12:28:41 10/23/13) Do you still have the part number for the check valve kit? We have the same problem on our 4020.

Larry

Larry
Which problem does your tractor have??

http://www.geraldj.networkiowa.com/4020si.htm

After glancing at this thread I may be incorrect.

 

[buickanddeere]

Agreed that the trans pump stops on a syncro when the clutch is pushed. And the primary function of the check ball in the circuit between the trans pump and the front pump is to prevent drain back during shutdown.
If the check valve is stuck open or missing. It's going to shorten the time the front pump can use reserve oil.
Certainly as you have stated. This tractor has a high pressure leak and/or low flow from the trans to the front pump.

 

[David G]

What happens when the reservoir gets empty?

 

[buickanddeere]

(quoted from post at 14:47:14 10/23/13) What happens when the reservoir gets empty?

Cavitation

 

[Tx Jim]

(quoted from post at 14:47:14 10/23/13) What happens when the reservoir gets empty?

Ideally the clutch pedal is only depressed long enough to stop then shift gears and change direction.

 

[tim s]

Yes B&D, that sounds like what they have,, If the trans pump is good the check valve is not needed much.

 

[David G]

Thus the front pump does not suck.

Thanks

 

[Tx Jim]

No the frt pump doesn't suck oil but can pump a lot at way higher than 2250 psi.

 

[Larry in WNY]

Jim,
Our 4020 will lose steering and brakes if the clutch is engaged too long. There is a chattering sound when this happens. Usually when trying to back up to something. We put it in park,give it throttle and the steering and brakes come back. I heard there was a check valve in the rear end that can't be replaced without removing the rockshaft. Another check valve can be installed inline near the front of the tractor according to some instructions I found on the web. I have a kit, but haven't tried it yet. I was wondering if it was the same check valve kit you used. My parts are at a different location so I can't get the part numbers right now.
Larry

 

[Tx Jim]

I still think all a check valve will help is hyd chattering on initial engine start-up. After initial start-up lose of hyd's by depressing clutch pedal(Syncro-range trans) is contributed to a massive hyd internal leak,weak trans pump or plugged hyd filter &/or sump screen BUT NOT CHECK VALVE.