JD 4020 SCV Leaks

NorthMNJD4020 · Apr 20, 2019

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

Billy Shafer · Apr 20, 2019

You will find that some of us. Older mechanics know what we are talking about. The new kids just know what the book tells them.

Bob Bancroft · Apr 20, 2019

You need to slide over to the JD forum and talk with Tim S. He's way out ahead of the crowd on these.

Tx Jim · Apr 20, 2019

NorthMNJD4020
I agree Tim S is a very knowledgeable person & an asset to this forum. It's always a very good idea to check stand-by pressure on closed center hyd systems such as your JD tractor has. Seals on those systems start failing above 2400 PSI.

NorthMNJD4020 · Apr 20, 2019

I'll move over to that forum and hopefully he chimes in. I'll rig that gauge up and see what I'm at currently.

Thanks guys

grizz02 · Apr 20, 2019

Billy your correct I used to fly a lot 100k a year I always said I would take a grey headed pilot with a hangover vs. a young inexperience one any day ✈✈✈✈

tim s · Apr 20, 2019

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..

Billy Shafer · Apr 20, 2019

griz02
I was called to a site. Where our expert was doing a 4 hour load test. Engine just stopped.I asked the expert twice did you check the day tank. He told me in a very rude voice. I know what I am doing and yes the day tank is full. I went over and kicked the tank. The guage went to zero. I pulled the inspection plate off. The float was stuck to a glob of what looked like mud. Six hours wasted because the expert knew what he was doing.

JD 4020 SCV Leaks

NorthMNJD4020

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Billy Shafer

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Bob Bancroft

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Tx Jim

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NorthMNJD4020

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grizz02

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tim s

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Billy Shafer

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