4020 hydrolics

I have a John Deere 4020 power shift that the hydrolics stop working after about 30 minutes of running. The hydrolic fluid turns milky looking. Have changed fluid and filters 3 times. No hydrolic leaks on the tractor. Any info appreciated. Thank you!

sounds like there was water in the system. Your pump might be hooped, Im not sure

Thanks for the reply. There was water in the system before I changed fluid and filters. What is the fix. Thanks again.

If your pump is hooped you have to change out your pump. Im not sure on those 4020s if they are external or internal pumps. This is just a guess of coarse. Best to get your local hydrolic shop to have a look before spending to much money

There are two pumps. Neither will work if the
trans screen is plugged, a trans divert valve stuck
pen. Or the trans relief valve stuck.
Are the trans oil cooler fins clean or plugged
solid with 39+ years of oily mud?
Is there a loader or any other hydraulic load on
the tractor?
Instead of willy nilly tearing the tractor apart
and installing random new parts. Trouble shoot first
with a pressure gauge and measure flow.

You didnt pull the tranny lockout lever on the left did you ????..When chainging fluid Drain all the plugs ,, There are 3 always change filters ,,, if you ar e gonna keep that Pshit, Get used to the idea of swaping out the fluidat least twice a yr ,,KEEP IT IN THE DRY <, Water has way of condensing Thru ,, wouldnt hurt toflush thrtranny case with deisel fuel , do notstart the tractor

An internal high pressure leak can make the oil be foamy too. It is not uncommon for a power shift to develop these type of leaks.

Take a sample of the foamy oil and put it in a glass jar. Put the jar into a pan of boiling water. When the oil is heated up and becomes clear the air/water/oil will separate. You can look through the jar and see what you have after it has cooled down. If it is all oil then you have an internal leak. If you have some water in the bottom of the jar then you still have not gotten the system cleaned out.

If it is an internal leak run the tractor and check for things heating up. Steering valve, SCV value, three point lift cylinder, brake valve and etc. I have an infer red thermometer that works well for this.

"It is not uncommon for a power shift to develop these type of leaks."

WHAT are you saying, jd "seller"???? (With NO JD knowledge.)

Outside of the transmission/charge pump the hydraulic systems of the PS and synchro 4020's are IDENTICAL, and there is NO difference between the two as to possibly having an internal high pressure leak.

WHERE do guys like you come up with these "old mechanics wive's tales, anyhow????

randy kunkel
A common problem on tractors with water in hyd system is a plugged breather cap on the hyd fill hole.. I second the only way to diagnose hyd woes is with a 300# &amp; 3000# gauges. Is the frt hyd pump coupler intact and pump shaft turning with the engine

Don't be too quick to fault jdseller on his JD knowledge. Few here have as much theory, practical and hands on experience.

(quoted from post at 08:36:21 07/03/11) Don't be too quick to fault jdseller on his JD knowledge. Few here have as much theory, practical and hands on experience.

Click to expand...

b&amp;d
I agree with what you stated about JDseller's knowledge but I have to agree with Bob that the "high pressure systems" on both PS &amp; Syncro- range are very similar on 4020's. The low pressure systems are a different story.

I have a Gulf Coast filter (the kind that uses a roll of paper towels as the filter media) hooked up to the return line on my DB 1212 to take water out. The return which is fairly low pressure is what it"s "T"d" in to and it"s return is a hose runs to a plug on top of the transmission. Takes water out real well and makes for some really clean hydraulic fluid, cheap too change too.

Bob and TX Jim are right on these hydraulic systems. The high pressure side is exactly the same. The low pressure side is way different. So we all agree on that.

Now look at my statement. "It is not uncommon for a power shift to develop these type of leaks" I could have stated that better as both transmission types can commonly have a high pressure leak. Here in north east Iowa there where a high percentage of the later 4020s sold with the power shift transmission. I have noticed in my working on them (30 plus years and JD certified on them) that the power shift tractors seem to get more high pressure leaks than the Synco-range ones. As to the why I don"t know. They are basically the same system on the high pressure side. Maybe more of them are used on loaders??? Don"t have a good answer but I have noticed that.

BOB I did not say the transmission was more likely to have a high pressure leak. I can see how I wrote it that you could read it that way.

Randy: your problem is not likely water after three changes. I would bet that you have a high pressure leak. As several of us have stated run it and look for things heating up. Then you can get back to us on here about how to check the part of the system you think is causing the problem.

You could have a leak in the charge side that is dumping all of the oil back into the sump. Usually this type of leak will be there all of the time, not changing with temperature. You would need to plumb a gauge into the charge pressure side to really tell.

Do some more investigating and let us know.