3pt hitch intermittently gets stuck in lowered position

I posted this on another forum and got a few answers, but nothing conclusive so far. That thread died so I'll see if anyone here has any ideas.

I've got a '64 Massey Ferguson 35 Utility, shuttle shift, two stage clutch, z134 gas motor. (same machine as a Massey 202, mechanically) When I got it for $1000, it didn't run and the 3pt hitch didn't work. I fixed everything, including rebuilding the hydraulic pump and put a new rockshaft cylinder/lift cylinder in. The hydraulics worked fine all summer while dragging my 8' 650lb flail mower around.

As winter got near, I modified a snowplow from a pickup to fit on the 3pt hitch. During the first storm, and every storm thereafter, at complete random when I lower the hitch (fast or slow, doesn't matter) the plow will lower, but the hitch will not raise. No matter how much I fiddle with the draft (usually set toward the back/up) or the position control, no movement at all from the hitch.

Every time this happens, I have to remove the dipstick cover from the right side heel area of the transmission, stick my hand in there, and manually bump the control valve lever. Then it pops loose and the hitch will come up. Until next time, that is.

When I got the machine, the rockshaft cylinder/lift cylinder was snapped clean off the top plate where it bolts in. I'm wondering if that maybe bent the internal vertical linkage causing it to bind? Or if maybe the draft control spring/linkage is not adjusted correctly? (when I lift the plow you can see the draft spring linkage flexing in from the weight of the plow)

Any thoughts as to what my issue is? I'm getting [i:a59b5cde92]very[/i:a59b5cde92] tired of taking that cover plate off, manually bumping the control valve, and putting it back together. It doubles the time it takes to plow.

Thanks,
-Chris

The hydraulic pump has an oscillator that rotates the spool valve back and forth slightly at all times. It's job is to keep the valve from sticking. Sounds like it's not working on your pump. If so the pump will need to come out to repair it..

(quoted from post at 09:25:46 02/13/17) The hydraulic pump has an oscillator that rotates the spool valve back and forth slightly at all times. It's job is to keep the valve from sticking. Sounds like it's not working on your pump. If so the pump will need to come out to repair it..

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I rebuilt the whole pump, new cam blocks, new cylinders, o-rings, etc. I'm 100% sure that it worked when I put it in, I spun it up with a drill before re-installing it, oscillator rocked back and forth perfectly. That is, however, the first mention of that, and definitely something I'm going to check out and makes perfect sense!

I hadn't even thought of it, thanks!

Editing is apparently disabled so I have to put in another reply:

What I don't understand is that all summer it worked 100%. It's almost like now that the hitch is going so low due to the low attachment points of the snowplow, the problem started.

Either way, I'm going to check that out. Can't be taking it apart now though, cold and I still need the machine to plow even if it takes forever.

The control valve has a series of washers on it. They are a very precise fit. If they are worn it will allow the washers to lean a little and can stick to the shaft. Usually manifests itself when things are cold. After it warms up and the metal expands it "should" get better but just depends on how worn they are. This is what the oscilator is shaking to try and keep this from happening. If you take the valve out the washers should not have any side to side movement more than a couple thousandths.

(quoted from post at 11:28:55 02/13/17) The control valve has a series of washers on it. They are a very precise fit. If they are worn it will allow the washers to lean a little and can stick to the shaft. Usually manifests itself when things are cold. After it warms up and the metal expands it "should" get better but just depends on how worn they are. This is what the oscilator is shaking to try and keep this from happening. If you take the valve out the washers should not have any side to side movement more than a couple thousandths.

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I rebuilt the entire hydraulic pump, new control valve and all washers and o rings. There is no play, all were a good fight fit.

I even put a new control valve spring in it, technically, the only old parts left in the pump are the main body itself (less the cylinders) and the oil pickup plate. Replaced the filter, too.

Thanks for the suggestions!

Rockypg is looking in correct area. Also make sure that the spool valve in not scored.

When you bump the control arm to make them go up does the arm actually move to a different position like further out? With both the draft and position arms up in transport is the roller on the control arm still pushing against the adjusting nut on the lever or is there a gap?

(quoted from post at 12:38:58 02/13/17) When you bump the control arm to make them go up does the arm actually move to a different position like further out? With both the draft and position arms up in transport is the roller on the control arm still pushing against the adjusting nut on the lever or is there a gap?

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Inside the control valve did not look scored when o was rebuilding, but I suppose it may be possible that I missed it.

When I bump the control valve it seems to pop back out a bit, but not much. With both draft and position control levers in the transport position, the lever is still touching the adjustment nut. I cannot tell if the lower roller is still touching the control valve rod or not. It's submersed in hyd oil.

If I get a warm day, I'll fiddle with the controls until it fails, then drain the fluid to see exactly what it's doing.

I haven't seen anyone else with this issue, and nothing in the factory manuals that describes it.

Ok one other thing to check too is the dashpot assembly. Make sure the plunger isn't bent and moves freely.

No dashpot on the 35, that came in on the later models.

(quoted from post at 13:55:30 02/13/17) No dashpot on the 35, that came in on the later models.

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Yep, no dashpot on the 35.

You guys have given me a few other ideas to think about that I didn't have before. Once I get a warmer day and some free time, I'm going to dig into this. It's my main problem with this machine, otherwise it does exactly what I need it to.

Thanks!