MF 135 3 point raises by itself

I've got a Massey 135 with the Perkins. When I'm bush hogging, the bush hog raises by itself, to the highest position. I've tried different combinations of position control and draft control but that doesn't help. I've also disconnected the top link to see if that helped, but no luck.

Sounds like a valve actuator adjustment.

Take the right side round cover off. Start it up and move the raise/lower lever, watch what happens. You will see slight moment of the lever where it pushes against the roller on the pump lever. Note which way the lever moves the roller. (I don't have my shop manual here, so can't get real detailed.)

If you don't see any movement, the linkage could be rusted in place. Those are known for getting water in the transmission case through the shifter boots and the draft link boot. If it's rusted up, the top cover will need to come off, everything cleaned up, freed up.

If you do see movement at the end of the lever, SHUT THE ENGINE OFF FIRST!!! Follow the roller lever down below the oil level, there will be a pivot point, then below that an adjustment nut. Turn the nut about 1/2 turn the direction you think it needs to go. Remember where it was, just in case...

Start it up, see if any improvement. If worse, go back the other way. If better, keep making fine adjustments until it works.

BUT UNDER NO CIRCUMSTANCE EVER REACH IN THERE WITH IT RUNNING!!!

There is more to adjusting the controls, but this should get it working. If not, a shop manual can explain it much better than I can here. It would be a valuable investment, especially if you have to take the top cover off and/or go into the pump..