John Deere 4320 SCV valve

[Farmall m farmer]

So the tractor SCV valve the detents inside do not work I saw you can buy a rebuild kit with new valves from worthington ag parts is this something that is rebuild able by just putting seals in it and put back together or is this something that a dealer should do or just buy a rebuild SCV valve?

 

[Tx Jim]

Detent components can be replaced. Probably failed detent roller but could be a failed o-ring. If the 4 poppet valves are changed or disturbed they will need to be adjusted using a dial micrometer or air pressure. Below are some photo's of YT long time member Tim S showing scv being tested on Tim's test bench & steering valve being adjusted with a micrometer.

Back when I served as a JD dealer service manager for 13 yrs I had several so-called mechanics under my supervision that couldn't get those valves adjusted correctly the first time & sometimes even the 2nd time. That is probably one of the reasons Tim built his hydraulic test stand. Tim S accepts ship in/ out JD hyd control valves for repair.

 

[Farmall m farmer]

So the actual hydraulic part of the valve is fine it’s just the detents can I just put new detent ball and spring inside without taking the valve out of SCV?

 

[Tx Jim]

One would only know if the 4 poppet valves are operating as designed if checked by attaching gauge to each breakaway coupler then operating control lever & monitoring gauge. I think if detent piston item 6A or 6B seal had failed that seal could be R&R by removing cover item 26 in 1st photo. Be aware if cover item 26 is removed more items such as items 17 & 18 will be loose from there bores. I think replacing roller will require disassembly of rocker item 6A or 6B & cam item 5 in 2nd photo.

 

[Farmall m farmer]

Update I put a hydraulic pressure gauge in the SCV and it read 2300 psi I still think I’m going to give it a shot at rebuilding them and see if I can get them to seal up again and get them adjusted

 

[Tx Jim]

Good luck.
One needs to check pressures in both sides of breakaway couplers in same housing checking to determine if pressure holds or rises or leaks off when control handle is returned to neutral position. Are you planning on resurfacing your scv poppet valve seats? Are you going to use a dial indicator to adjust valve clearances?

 

[Farmall m farmer]

Good luck.
One needs to check pressures in both sides of breakaway couplers in same housing checking to determine if pressure holds or rises or leaks off when control handle is returned to neutral position. Are you planning on resurfacing your scv poppet valve seats? Are you going to use a dial indicator to adjust valve clearances?

I did not do that I will do that why I found odd was as soon as I let the control handle back to neutral position it bleeds off immediately. I am planning on seeing if Deere can just resurface them for me. And yes I am planning on using a dial indicator to check clearances

 

[Tx Jim]

Gauge returning immediately to zero when control handle is returned to neutral indicates poor seating areas or valve clearances between roller & rockers are too close.