MF 65 3 Point issue

I've got the Massey 65 in the shop adressing a few issues. One of which is the 3 point hitch. It bobs or adjusts itself every second or 2 when I have my mower or brush hog on it. I'm assuming I have a leak somewhere.

Tractor has the 2 spool aux control valve. When I put the valve that
controls the 3 point in the neutral or off position, the hitch seems to hold fine. When it's in position to operate, back to bobbing. With tractor off, it
will hold load fine in off position, but as soon as I move valve to the
operate position the load will drift right down.

This leads me to believe the problem isn't in the lift cylinder. I pulled
right side cover hoping to see oil spewing from an end of the standpipe,
but no such luck. I'm assuming the issue is in the pump somewhere, most
likely the control valve, but thought I'd see if there might be something
I'm missing before I start digging.

Any other possibilities before I pull stuff apart and can't troubleshoot
with tractor in one piece?

Thanks, Jeff.

I doubt it's the control valve as it's on the pump INLET, has to be pump valves/pistons or can also be stand pipe O rings leaking.

Your problem could be a worn control valve or the hardened steel sealing washers. I worked on a customer's MF 35 many years ago that had a very similar problem to yours. We replaced other parts found to be worn and still had the same problem. When in the transport or "hold" position, pressure oil from the cylinder is captive in the discharge (rear) section of the control valve chamber. The discharge slots on the control valve are situated outside the rear washer at this point. Oil leakage from this chamber is proportional to the amount of clearance between the valve and the centre and rear sealing washers. Badly worn hardened sealing washers can be "rocked" sideways when placed on the control valve & is very noticeable, as are wear "grooves" on the valve.
As Dieseltech has said, I'd be looking at the exhaust valves and seats in the chambers, as pressure oil in the cylinder acts on these as well. Remove and test the relief valve for leakage. Replace the stand pipe "o" rings as a matter of course. Worn pistons and /or rings will only come into play in the lift position and usually show up as a "shuddering" while lifting, but don't come into play while in the transport position. Interested to see what you find, Evan.

Well, I pulled the pump. What a pain.... It was supposed to just pull out after disconnecting. My tractor has multipower and between the bracket and gear for the multipower, I couldn't get it out no matter which way I tried. I ended up having to take to inlet/filter housing off the back to sneak it out.

Anyways, I put compressed air to the outlet of the pump to see if I could see or hear anything leaking. I had all kinds of bubbles around the valve chamber caps. Bingo, I think. New o rings and good to go.....

I pulled cap and valves from one chamber. The valves didn't look too good. Not nice and smooth like I'd like to see. Seats aren't so hot either. Maybe a few more parts, but salvageable.

I pulled the rest of it apart to find one of the main bushings seized onto the camshaft and spinning in its bore. I figure at this point I'm done trying to fix it. I ordered a new pump.

Could it be the draft control adjustment? There is a clevis for the top link that has a spring assembly that lets pressure off to keep the plow or implement at a constant level.