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| We have a early model John Deere 4020 that has always leaked oil out of the couplers. This winter I put a new scv valve under the hood and it still leaked so sent it back and got a new one and same thing. The previous valve was checked and it was fine. After checking pressures and unhooking lines we figured out the oil was coming from the bottom of the steering column. We ordered a new column and put it on and it still leaks. So what else could it be and where else do I look. Thanks |
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Fruita CO | Have you rebuilt the couplers themselves? that's where the problem is, & they are 10 times cheaper & easier than all the other stuff you've done.
There will always be some back pressure in the return side of the system when the valves are in neutral... |
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| I have rebuilt the couplers. If the lines are unhooked right above the couplers the oil just runs a steady stream but it takes maybe a minute till it runs out. It is like it has to build up pressure. Also the pump pressure is where it needs to be, maybe even a little on the low side. Even with the valve linkage unhooked and in neutral it still leaks out the couplers.
Edited by JJP 6/3/2014 20:17
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ND | Install a seal kit in the couplers with the o-ring and backup ring. You should have been a doctor starting every place except where the problem is. |
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| So your saying that there should always be pressure in the lines to the couplers? Cause that is what is happening
Edited by JJP 6/3/2014 20:43
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| Did you put new steel balls in the tractor coupler ? the spring behind the steel ball ? |
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| Every single piece in the coupler has been replaced. Bought new barrels, balls, springs,seals and orings. My main concern is that there is steady pressure in the lines all the time. The valve is in neutral, the couplers are fine, but what else is there. |
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SW Ohio | I'm confused, is it leaking at the rear where the hoses plug in or is it leaking under the dash near the steering valve? If you rebuilt the rear couplers as good as you say it should hold full system pressure anywhere all the time hoses or no hoses. |
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Fruita CO | There is nothing else...As I said above, there will be back pressure in the lines. If the couplers are right, they will not leak. You're not turning the levers with nothing plugged in are you? They WILL run oil out if the lever is open...no 2 ways about it, that's normal.
To check the SCV valve, plug a gauge into the coupler. Manipulate the lever to get 1500 PSI on the gauge, then let it go to neutral. Not that easy, but it can be done. It should take one minute for the pressure to go from 1500 to either 2000 or 1000...if it goes up, the pressure valve is leaking; down, the return valve is leaking...normally, some leak-down is OK.
The normal leakage will pressure up both ends of a cylinder & basically lock it in position. If the leakage isn't fairly balanced, a cylinder will creep.
Edited by ronm 6/3/2014 21:20
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| Well , start checking for cracks in the coupler housing .... unless i am confused too ! |
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| The oil is leaking out of the couplers in the back at a steady drip all the time but if you undo the lines at the coupler the oil runs out in a steady stream. So tell me if I am wrong. As I see it if there is always pressure in the lines the cylinder will creep up. if I put in a pressure gauge in the line at the coupler, at idle and not using the lever how much pressure should there be? |
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Fruita CO | The valves in the SCV do not seal up perfectly...read my post above about pressure in a cylinder. Your couplers should not be dripping oil all the time...if you rebuild them right, they won't leak. Unless you have the ISO conversions, they are a POS & almost impossible to seal up... |
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| The return line of that vintage 4020 SCV is to the oil cooler/reservoir up front held up to about 200 psi by the charge pump in the transmission. So minimum pressure is about 200 psi even in float. I can't manually close a single acting cylinder with the tractor running, I have to kill the engine to let me push that cylinder in to fit it to an implement. The SCV returns to the cooler/reservoir because the front pump moves up to 22 gpm and the charge pump only moves about 4 or 5 gpm. The cooler/reservoir makes up for the difference in the volumes on each end of a cylinder.
Gerald J. |
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Fruita CO |
Yep, it depends on if it's a syncro or powershift...which the OP hasn't specified...PS back pressure will be trans. pressure-175PSI. Syncro will be oil cooler back pressure-100-120PSI at most...
Either way it's a non-issue, the nature of the beast... |
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John Deere 4020 Hydraulic Help
