I made 2 passes down the field today when the plows lifted by themselves and oil was spraying like it blew a hydraulic line. I tried lower the plows again and they wouldn't go down. Strange. 

I hopped off the tractor and found the oil to be coming from one of the lift cylinders. Crap. 

I jumped back on the tractor and got them to go down. They lifted again, this time they just wouldn't go down. 

I drove it back to the garage, shut the tractor off, and they went down. If you started the tractor back up they'd lift again. 

I checked the linkage from the controls to the valves and they are connected. 

I'm stumped and am hoping someone here can point me in the right direction. 

I had to call on my Massey to do the rest of todays plowing, I'd REALLY like to do the rest with my Allis. 

Thanks. 

What is causing the pressure when it shouldn't be there is what I'm looking for. 

I sure does look good though. 

A bit bigger than the Massey;

The 7000 got a little beefier when we swapped the front axle out of the 7040. The 7000 needed front tires, the 7040 had good fronts but the rims didn't fit, so why not. 

how did you have the traction booster and the position levers set?

The first 2 passes I made it worked great, thats why i'm shaking my head. 

What is causing the cylinders to lift on their own, and not go down unless the tractor is shut off. 

The way it is now I think I could rebuild the cylinders and they may just go again. Then again, I could be 100% wrong. Maybe they need the back pressure to move a valve???

I'm at a loss. 

The way I'm reading this the first thing I need to do IS get the cylinders fixed, as it looks like backpressure is part of the deal. I'm thinking it's not the only part of my issue, but it's a start. It does look like - if I'm reading this right, that unless the cylinder creates enough back pressure it won't kick into bypass. 

I'm still open to other information.

Too much pressure will blow the side out of pump long before cylinder seal.

Dr is right on what he said.   MACK

The cylinder seals should be here tomorrow (Monday) and nothing but rain here for the next week. If I can get at it I'll get the cylinders done and take a look at the plunger too. I'll see if I can get the Traction Booster cable freed up while I'm at it. I have a spare cable off my 7040 parts tractor I can probably make work if needed. 

With the rain coming I finished up most of the plowing yesterday with the Massey. We still have one small field left to go, so hopefully I get a chance to make sure it works as it should before next year. 

Morley  

Just an update on this one - you were 100% spot on. 

I put the rebuilt cylinders on tonight, no more leakage but they weren't real willing to go down. I pulled up the outer plunger and everything seems to be working as designed. 

I was only able to do a quick test as the sky opened up and I got soaked. It looks like we have a few decent days coming. If things dry up any I'll hook up the plows again and give it a run. 

BTW the original cylinder seals were in ROUGH shape. 

Thanks again. 

I searched to find your post,curious how you made it,does it work now?