Three point hitch dead-heading?

[quicksandfarmer]

So I thought I'd throw this out to the assembled wisdom...

Yesterday I put the flail mower on and headed out to do some mowing. I lifted the mower up all the way for transport, and as I did I thought, "it usually doesn't go up that high." Then I noticed that the engine RPM had dropped from 2400 to 700 and sputtering, and then hydraulic fluid started spraying out of the pump. Once I had lost about a gallon the mower dropped and the engine returned to normal. Fortunately I don't seem to have broken anything, the outlet hose from the pump was leaking and I was able to tighten it up and it stopped. I filled the hydraulic fluid and mowed all afternoon with no ill effect.

So my working hypothesis is that the 3-point lift cylinder over-extended and dead-headed the pump. Is this plausible? Has anyone seen this before? My lift is kind of erratic and I want to rebuild it anyway, will that help?

Thanks.

 

[Leejohn]

Feed back linkage needs adjusting. Your manual should tell you how.

 

[greg_g]

Yup. There's an adjustable rod that's supposed to stop the upward lift arm travel before it reaches the point you experienced. Pretty sure it's related to the lower assembly in this diagram:


//greg//

 

[RonMar]

There should also be a hydraulic safety relief on the 3PH control valve body. Not familliar with the 354's valve specifically, but there is probably a screw in plug on the valve body, most likley has a square top. Under that plug, if it is the relief valve, you will find washers, a spring and a valve core resting on a valve seat down in the hole. The stacked washers are how the relief pressure is determined. It would probably be a good idea to "T" in a pressure gauge into the system main supply line and see where that 3PH relief valve is releasing, if at all... My 3PH control valve safety relief was opening in excess of 3K PSI. It popped a couple of spool valve Orings on the loader valve while working with my 5' brushhog, which was my initial symptom that got me looking at the system pressure. Removing one washer and shaving a little bit off the thickness of another got the relief point down around 2200 PSI.

 

[quicksandfarmer]

Feed back linkage needs adjusting. Your manual should tell you how.

And therein lies the rub. I have the liftbox with a single control lever for both lift and draft, my manual is for the dual control lever model. Jinma being Jinma.

FWIW the pressure relief works fine if I try to lift something too heavy.

So I think what I'll do is take it apart and fiddle with it, see if there are any parts that look obviously broken.

 

[quicksandfarmer]

So I want to update this to see if the brain trust has any thoughts. I noticed today that the top link -- which I only use for the mower -- is bent. It's bent down, i.e. the mower was lifted too high and the top link couldn't pivot enough. When this happened there must have been significant force on the top link attachment point. I have draft control so I imagine when this happened the draft control must have been pulled out all the way. With the lift up all the way draft control should be disabled, but is it plausible that this was causing the valve to dead-head?