Power major valve control chest o ring question

caltor · Dec 11, 2021

I completely rebuilt the hydraulic case on my Fordson power major. Put in about 20 new O rings and 8 new gaskets. I'm not the most experienced person mechanically but I followed the manual and watched many videos online. When I dismantled the valve control chest I did not find the O ring that is marked in red. So I did not put a new o ring in. But my hydraulics seem to work great except when I brought the arms all the way to the top, at that moment a hydraulic lock happens every time and I cannot move the control lever either way it's stuck in the middle. I have to shut off the tractor and find a way to relieve the pressure. So after doing a lot of thinking about that o ring I experimented, cause I could not tell where it went. Nears I can tell it goes underneath the Spring guide. So I put and o ring in this position and and the hydraulics seemed to work excellent and did not lock up anymore. However today I used it for snowplowing for about half the day and I found that with the snow plow on it won't lift up all the way and it is slow also. Does anybody know about this o ring and where it goes for sure?

Majorman · Dec 13, 2021

The O ring goes under the top plate on top of the spring holder. Should not give the problems you are getting though. The valve is the unload valve and many have had washers placed in that position to increase the lift capacity.

If too many are used or if that valve jams, the pump may be damaged and it is best to use a pressure gauge when altering anything in that area.

caltor · Dec 14, 2021

So the o ring should sit right on top of the Spring guide and the cover plate presses down on it on it which in turn moves the Spring guide down by the thickness of the o ring, is that right?
So the o ring that I put underneath the Spring guide I should try to fish that 1 out correct?
Thank you so much, I really appreciate your help.

Majorman · Dec 14, 2021

I checked in the workshop manual and there is a bit of confusion. The seal (O Ring) is only used on the early versions of the unload valve. There were three different valves used. On re-reading your post. It seems you have the latest version which does not use the O ring and just uses the paper gasket.

The earlier unload valve had a plunger under the plate and the ring went on the plunger.

Sorry, should have checked the workshop manual and not the parts book. That shows the latest valve without the plunger and shows the ring under the plate.

So you can delete the ring.

caltor · Dec 14, 2021

Thank you very much for clarifying that. I have read a million posts by you in the last few months, I really appreciate all the knowledge.

Power major valve control chest o ring question

caltor

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Majorman

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caltor

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Majorman

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caltor

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