JD 4020 Hydralic

[Dougin texas]

Early model JD 4020 when hooked up to JD 535 baler the baler door latch will not stay closed. I have hooked up to two different tractors and the door hatch stays close. I hooked pressure gauge to SCV and have 2100#, but pressure will start to bleed back off to about 1200# and then it will start climbing again. Everything with hydraulics seems o work fine, just that when hooked up to baler the door latch will not stay closed. Any ideas.

 

[Tx Jim]

SCV needs new valves with clearances adjusted

 

[Mike M]

You have a problem with the control valve. Not sure how to adjust them ? there are likely check valves in there leaking off too. Our 4020 has one that builds pressure with a gauged hooked to it but I never use it so I never tried to figure it out.

 

[Tech 7]

The SCV is leaking internally and will need to be rebuilt.

 

[ss55]

Have you tried reversing the hoses at the coupler to see if the leaking valve will then reverse pressure to keep the door closed?

 

[Mike Aylward]

In addition to the other good information given one thing to check on these valves is the thermal relief valve which is in the front cover of the valve. As the relief valve spring weakens over time hydraulic pressure is bypassed and causes problems similar to what you are experiencing, mostly with light load or single acting cylinders. If the valve is in adjustment and the housing is not cracked this is something to check. Mike

 

[Tx Jim]

Mike
Are you referring to relief valve(key 36) as the thermal relief valve? If so I don't remember that valve being a thermal(heat) valve.
Thanks,Jim

 

[Tx Jim]

Forgot to upload photo. I hope Chris reinstated the edit function SOON!

 

[buickanddeere]

TimS can make that SCV valve better than new . Is the coupler worn out ?

 

[Tx Jim]

b&d
If I remember correctly Tim doesn't like to repair this style valve. I think they are a PITA to set clearances but it's been a long time since I've seen inside one of them.
Jim

 

[Tx Jim]

Ditto what Tech 7 stated.

 

[Dougin texas]

Thank you all for the comments I had to purchase reconditioned SCV, was going to have mine rebuilt but was told the seats were pitted/beat up and it could not be rebuilt.