Here is what the check valve looks like assembled:
It's a little hard to tell from the photo, but the O-ring, that seals the valve, is brittle and flat. Not likely to have been working properly.
I researched the function of the check valve in three shop manuals - one for the Ford 9N/2N/8N, one for the Ford Golden Jubilee, and the one for the Dexta. In each tractor, the check valve is designed to keep the hydraulic lift arms in position when raised. If the arms do not maintain position - or are "bobbing," it's likely that the check valve is at fault. It could be from a broken spring, poor seating of ball to mating surface, or a leaking O-ring.
I am keenly aware of this problem, and am glad to have been able to remove the check valve from the Dexta's hydraulic lift cover. My Jubilee is presently suffering from these exact symptoms. The lift arms raise reluctantly, then bob up and down. I've been trying to figure out why. Now I know, thanks to my work on the Dexta. I guess it's a case of killing two birds with one stone.
Removal of the Dexta's check valve wasn't as difficult as I first thought. For one thing, there are ports directly above and below the valve chamber, so I was able to squirt penetrant all around the valve components. I elected to leave the actual valve seat in place - no need for it's removal in order to clean the other parts. Also, note the tip of the valve cap. It's grooved, so it's not too difficult to get a grip on it with small pliers. Once loosened, I was able to twist it out.
Check off another repair, and on we go.
Don