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1966 MF 135 deluxe gas Z-145 hydraulics lift jerky motion?

Barry Williams I purchased this 1966 MF 135 tractor from son in law needing a lot of TLC. Last winter I went over whole tractor servicing it and paint too. ONLY problem but a big one is hydraulic lift arms move up ward in a jerky motion? I cleaned filter and new 8 gallons of M-1129 fluid. Tractor looks great and runs great but hydraulic lift arms raise in a jerky motion.

I did a pressure test and the hydraulics have 2400 pounds of pressure which is in specs for this tractor.

Thanks if any body knows the fix.

ponymare Sounds like its getting air in the system.
Barry You are the second person that told me I had air in the system with the jerky hydraulics. How do I bleed it out? It must be up top in the piston ram cylinder do you think?

Thanks, Barry

ponymare Have you raised the arms completely up, then all the was down several times? That should bleed the system of air. If it continues to get air, the ram seals may be bad, letting air into it when the arms are lowered.
Barry Yes I have raised and lowered the lift arms to their max several times but still have the air in the system that gives the jerky motion to the lift arms as they are raised.

Thank you for your answer on the ram seals might be bad.

410 482-6607

AJ As the pump strainer is clean and the oil new I would guess that a delivery or suction valve in the pump has an issue,the pump is a four cylinder piston type pump,if a valve is sticking the symptoms are like an engine missing,i.e it pumps three shots and misses one leaving a gap in the movement hence the jerky motion,I am taking it the pump strainer is clean.

Barry Hey AJ,

I cleaned the whole sump area took the filter off and cleaned it very good. New MF 1129 hydraulic fluid. It holds 2400 pounds of pressure I checked that and the arms will stay up with out dropping down.

Lifting like I said, is jerky motion all the way through the lift.


AJ With the lift holding up its saying that the cylinder and control valve is ok,the jerky movement can caused by the oil flow not been constant,when you tested the pressure did the needle fluctuate at the fully raised position or did it hold steady,have you got a manual for the tractor.

Barry Hey AJ,

I used a 3,000 psi gage while testing and my tractor held 2400 psi. The needle was steady not jumping all around. I do have a manual and it says early pumps and mine is 1966 they started making this series in 1964 the 135 deluxe so mine is early model I would say and they are suppose to hold 2350 psi. The later pumps are suppose to hold 2550 psi. Mine holds 2400 psi.

Thanks big time for your input!


AJ The needle holding steady is saying that the relief valve and cylinder is ok,as there is very little can be done with the pump in situ I would remove it and have a look at all the moving parts,I worked for years on Poclain equipment that used piston type pumps,when a delivery/suction valve was faulty the movements would be jerky and the line vibrate like a jack hammer,internal hydraulics are great but have the downside if there is something leaking it can't be seen.
Good luck

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