early 3020 SCV

First off, I've rebuilt the valves on a 4020 but it was for someone else & I never really knew what problem was experienced before the work. They worked very nicely when finished! Levers operate with about the same feel when it's working as when the engine is not even running. Now I have my own (a 3020) and I thought was giving me trouble just from too rapid a response which I know is adjustable. Yes I have the shop manual as well as the owners manual plus TP in the tool box! I have however never experienced such wild performance from a hydraulic cylinder as this! Are the following items you guys have experienced & I wonder if they're likely fixable by simple maintenance repairs/rebuilding of the SCV?

I first used it on a sickle mower & lifting response was little short of violent. I thought it mostly the mower. Next I put it on a plow & found the same difficulties. If I lowered it slowly by a slight pull on the lever it would lower slowly and quite nicley. But.... when I let go for it to stop it extended again to the stop with almost violent speed then cancelled as though I'd shoved the lever fully forward to its detent. The only way I could lower the plow was to go all the way to the lower detendt position let the valve cancel & then raise slowly. Then it would stay. One time it unhitched. I stopped before I lsot both hoses but I did loose one. Cleaned it plugged it back in & when I opened the valve, the plow jumped to the full raise position. The lever in the dashboard was in neutral to begin with. One time I was trying to slowly lower it just to let it cut a bit deeper. The SCV began a metallic rattle sounding like the cams inside it were being hammered and it sucked that ram in like it was a pneumatic cylinder from which a load was suddenly completely released. That was the second time it unhitched.

All that said... Steering an brakes appear flawless. 3 Point had problems when I got it but they were all caused by whoever last assembled it. Now the 3 point too works very nicely with steady predictable response. It does fall completely when shut down but it takes about a day and a half to do that. Standby pressure is less than the width of my gauge's needle (low side) of spot on. All things seem (to me) to point to a beat SCV. Can that alone cause such violent behavior? The SCV lever seems to fight you a bit as you operate it. The lever goes in little fits & jerks. In my mind I keep thinking worn cams and mal adjustment with maybe some bad seals or O rings in the SCV.

Any opinins or suggestions?

PS... with the exception of the odd behavior when operating, once found it holds any position just fine!

Thanks.
 
I had an SCV on my early 4020 which would raise the loader all by it itself on occasion! If I recall correctly, we eventually figured out this was a very early SCV added as the second one on this 4020. No one could seem to fix it. I finally installed two (matched pair) SCV's off a utility tractor. Same basic valve, but a little longer, and with different valves in it. I think I still have the original good one, and the junk one here.
 

Sounds as if the valve clearances are too close on the poppet valves or possibly a roller on end of valve is bad. If It were mine I'd send it to Tim s so he could repair & test it after he gets back from his "road trip".
 
Those early valves are a different animal to repair,,and not always succesful, I would swap it out with a used one...you can not up-grade the poppets with the newer nylon seat ones..
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top