JD 4020 SCV Leaks

Per the advice from another member I figured I'd post this here too:

I've been struggling with some SCV leaks for about the past year on my 67 4020 (valves under the dash). I had them off to the dealer 7 times (yes 7!). One of the last older mechanics there finally got his hands on them the last time I brought them down. He said the o-rings between the two valves were blown out so my pressure needs to be adjusted down. He also said there are no cracks in the valves and this should solve the issue. What are your guys thoughts on this? I was going to rig up a pressure gauge today to see what my outlets are at. Could it be that easy? I'm a bit skeptical considering all the back and forth I've had with them.
Thanks

It would be best for you. To have all the information you can for Tom. Model serial number. What it is doing what you have done do
it. I get request all the time for help with Onan units. But most of the time very little information to go on. Makes it hard to
help.

Sorry that should be Tim.

I posted on the other board but here it is again to help others..
The older style SCV's are a bit ornery to repair..but they do stay dependable for years,, the basic leaks on them are the lever shafts and the packings,top and bottom, these can be dealt with fairly easy with basic knowledge,,higher than normal pressure is not normally a reason for leakage, but the older systems do better if kept in the 2250psi range, rarely do they build up higher on their own. the lever shaft o-rings get a work out over time plainly because they are worked,, packings just get old..remove the valve and cover and you can see how the roll pin removal lets you remove the shaft seals, just pay attention to the lever position, don't take the valve completely apart,,you will find this to be a simple job and will eliminate that nasty leak cooking on the exhaust manifold.. The newer gen SCV's do require a complete O/H,, and I do a lot of them here, using some improved seals and methods of repair, which I have shared on the John Deere board.

More information for all:

I attached a work summary for what I had completed last summer. This was still one of the "newer" guys who did this work (5th time the valves were off). Got the work completed, put them on and the hydraulics crept on the first outlet so I had to remove again for further adjustment (6th time). Once that was fixed, the valves held up for around 50 hours and then started leaking again. I just recently found time to take the valves out (7th time) and that is when the veteran mechanic swapped the o rings sandwiched between the control valves and mentioned the pressure settings I stated in the original post.

I got the valves back on today and plugged a pressure gauge in to the outlets and had around 2150-2200 psi which seems to be in the ok range correct? Could JD have damaged those o rings when I sent them back down for the 6th time. Do I put the hood back on and see how long it goes this time?

Another item I thought I should also mention is I took out the steering valve under the dash last summer at the same time as the 5th SCV trip and had that rebuilt by JD. It had some external leaks that I wanted fixed.

Tractor SN is 155299

Thanks


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Well they started leaking again between the two valve bodies today. Now what? Something must be warped/cracked right on one of them? Experts please chime in. Even though its snowing up here today hay season is creeping up on me. I've already got over 1000 bucks into these with no success.

Thank you

I know this is probably is not the answer you're seeking but have you considered mounting a 2 spool valve similar to control a frt end loader & eliminate your leaking scv control valve? I always thought JD engineers made the scv & steering valve components way too complicated. A simple spool valve will accomplish almost the same thing for operating cylinders as the complicated scv valve.

I'm getting close to that point, been fighting this leak for a couple years now. What's a replacement valve going to cost me if I do bite the bullet and open my wallet one more time?