Massey Ferguson 35 Three point linkage suddenly weak lifting

[FordnMassey]

Hi,
My MF35 has lost it's lift power on the three point linkage. I occurred after I was installing a diverter valve to the the external cap. The stand pipe was lifted clear when the external cap was removed, so I replaced the o-rings (Sparex supplied) and their backing washers top and bottom. The linkage has the following signs with either the new diverter valve or the (original) external cap:
1). TPL lifts much slower than usual
2). TPL can be pushed back down with my weight on the lower links from any level I set it to using position control lever.
3). the TPL falls to the lowest level within 3 seconds of turning off the motor without moving the position lever
These are all new since I began this install of a diverter valve. Previously the TPL could lift around 600kg (1300lb) and pop the front wheels in the air if overloaded.
Any ideas on solving this one?
Thanks for your thoughts

New findings:

I removed the side inspection plate that contains the dipstick and confirmed that the stand pipe was in place. I checked the orings at both ends and also confirmed that both ends "snap" into place snugly. I then cranked the motor and the stand pipe produced oil. I then cranked the motor with my thumb blocking the stand pipe and I was able to block the oil flow.

I'm guessing that this is a pump or relief valve issue. Any suggestions as to what's likely to be the issue?

 

[Cougsfan]

It would seem strange for the pump or relief valve to fail solely due the installation and removal of a diverter valve. You obviously have a leak somewhere. You have seemed to confirm the leak is before the stand pipe but there aren't many places for it to leak before the stand pipe. (??) You got me! Changing the relief valve is fairly inexpensive and easy to do so that might be worth trying but again, it seems strange it would suddenly fail. The pump would be expensive and a fairly large job, and doesn't seem likely to fail in the manner you have described. I wonder if you somehow dropped a small rock or something back down the stand pipe and it it is stuck in the relief valve (just a wild guess). Can you run the tractor with the side inspection plate off and look for oil gushing out of the pump area some place where it shouldn't? Might have to lower the oil level a bit to do that.

 

[Cougsfan]

If you drained all the oil out of the tranny area (a pain to do) you could pour some oil down the stand pipe. It shouldn't leak out. If it does you could see where it was leaking.

 

[FordnMassey]

That's a neat trick. I'll do that. Thanks.

 

[FordnMassey]

Hi,

Pump is removed from tractor and I found one valve assembly pushed out of the housing - see photo. There may be other issues with the pump as well, so I'm considering just replacing the pump with new from Inside via eBay.

Does anyone know how to tell it the pump in the photo is a Mark1 or Mark2? Does it matter if I swap Marks?

Anyone have experience with the pumps coming out of India?

Thanks for your thoughts.

 

[FordnMassey]

Hi,
For people who may find this useful in the future:
Rebuilt it with a cylinder block, rings and seal kit. It's not hard.
My advice would be mark the alignment of all control valve parts: I didn't and mine is now sticky - it only drops the tpl if the pump is turning which can be annoying when parked.
That burst valve was not causing a diagnostic spray of oil when I looked through the inspection cover.
Enjoy

 

[Jerry/MT]

Hi,
My MF35 has lost it's lift power on the three point linkage. I occurred after I was installing a diverter valve to the the external cap. The stand pipe was lifted clear when the external cap was removed, so I replaced the o-rings (Sparex supplied) and their backing washers top and bottom. The linkage has the following signs with either the new diverter valve or the (original) external cap:
1). TPL lifts much slower than usual
2). TPL can be pushed back down with my weight on the lower links from any level I set it to using position control lever.
3). the TPL falls to the lowest level within 3 seconds of turning off the motor without moving the position lever
These are all new since I began this install of a diverter valve. Previously the TPL could lift around 600kg (1300lb) and pop the front wheels in the air if overloaded.
Any ideas on solving this one?
Thanks for your thoughts

New findings:

I removed the side inspection plate that contains the dipstick and confirmed that the stand pipe was in place. I checked the orings at both ends and also confirmed that both ends "snap" into place snugly. I then cranked the motor and the stand pipe produced oil. I then cranked the motor with my thumb blocking the stand pipe and I was able to block the oil flow.

I'm guessing that this is a pump or relief valve issue. Any suggestions as to what's likely to be the issue?

Do you see any oil leaking from the lift cylinder? Do you see any leakage from the gaskets on the pump side plates? If your relief valve is stuck open it will make a racket and there will be a lot of activity in the oil by relief valve. Is the control valve stuck in the exhaust position?

 

[ScipioUSA]

Hi,
For people who may find this useful in the future:
Rebuilt it with a cylinder block, rings and seal kit. It's not hard.
My advice would be mark the alignment of all control valve parts: I didn't and mine is now sticky - it only drops the tpl if the pump is turning which can be annoying when parked.
That burst valve was not causing a diagnostic spray of oil when I looked through the inspection cover.
Enjoy

Thanks for posting back with your findings.

That's odd that it won't drop unless the pump is turning. Is that with your diverter valve installed also?

 

[FordnMassey]

Thanks for posting back with your findings.

That's odd that it won't drop unless the pump is turning. Is that with your diverter valve installed also?

The control valve has an tendency by design to stick. M F added a "wobbler" that jiggles the valve when in the pump is in motion. Works well, when it's running.
And with a diverter valve in place, the TPL can only be lowered or raised when the diverter set to the the TPL. But that's normal for this configuration on this machine.