1951 Ford 8N- lift arms weak and slow. Suggestions needed.

[tmac196]

As above.

Tractor is used daily to pull a PTO-driven manure spreader. The tranny/diffy fluid was changed about 200-250 hours/2 years ago with Soundguy-approved TSC UTF. The UTF fluid is at the correct level at the dipstick on the diffy and appears to be without water in it. Tractor has been kept inside for years, but lift arms have not been operated during this time. The hydraulic control lever was in the "position control" position while I was trying to operate the lift arms. I cycled the lift arms several times to see if this would help, but to no avail.

The lift arms cycle promptly without any load on them, but are slow or don't lift when attached to an implement and will slowly lose pressure and lower the implement while the hydraulic touch control lever is left in the up position and the engine (and PTO) are running.

Suggestions?

 

[Fawken]

Likely got some rough spots in the lift cylinder from not being cycled for such a long time. Is there a drop speed control knob on the head (top hat)? If so close it with lift up and watch for droop. Or if it isn't too tough, pull the top hat and inspect the cylinder.

 

[mapper]

I think that the regulator/position control valve is the likely culprit here, if the lift piston was leaking it would stay up while the tractor is running and drop after shutdown. The control valve assembly is located in the base plate of the hydraulic pump, there is a certain amount of adjustment and diagnosis that can be done from the side access plate but to work on the pump you will need to remove it from the transmission case. To remove it you will need to drain the transmission/hydraulic oil and pull the pot shaft, the pump can then be dropped out of the bottom of the case. Before doing this I recommend you get a good shop manual and read up on adjustment and diagnosis.
Also be prepared with new gaskets and bolts, the torque needed stretches them a bit. When reinstalling the pump glue the gasket to the case with gasket cement - Formagasket works well, the pump has to go up then slide forward a bit, keeping an unsecured gasket in place is almost impossible. This is necessary because the high pressure fluid route is through the baseplate to the lift cylinder, about 1500 psi.
Good luck with this.

 

[Fawken]

.... if the lift piston was leaking it would stay up while the tractor is running and drop after shutdown. .......
Good luck with this.

If it is leaking more than can be compensated for by the control valve and the capacity of the pump then no, they would drop with an implement load which is what he says is happening. On older machines I always prefer to check the lift cylinder before messing with the spools.

 

[Soundguy]

He needs to open the inspection port with it running under load and look in to see if there are leaks.

Prime leaks are cyl mouth, cyl to top cover, top cover to center section at the rich front inside corner, chamber side covers to pump housing, etc. There are others, but are below oil level, and require more instruction before further troubleshooting.

Lastly, check to make sure that with 3pt control up, that the control arm visible thru inspection port, is keeping the rocker valve in.

There is no cyl stop knob on this machine... Not factory anyway.

 

[Fawken]

Thanks. One of you guys need to donate an 8N to me so I can see how Ford "used to" do things.:laughing:

 

[Fedup]

Thanks. One of you guys need to donate an 8N to me so I can see how Ford "used to" do things.:laughing:

Or maybe you could just offer advise on machines you know something about?

 

[Fawken]

Or maybe you could just offer advise on machines you know something about?

Maybe. Ford lift arms and cylinders are fairly simple and somewhat universal in design and operation. Think of it like this: Would you stop to help a woman change a flat tire even if you preferred men?

 

[tmac196]

Thanks for the advice. When time allows I'll take a look through the inspection port and let you know what I see. I know nothing about hydraulics, but the Owner's manual, the shop manual and several YouTube videos have made me less ignorant already.

 

[Soundguy]

Maybe. Ford lift arms and cylinders are fairly simple and somewhat universal in design and operation. Think of it like this: Would you stop to help a woman change a flat tire even if you preferred men?

8n and 9n are simple and somewhat common to each other, naa is its own job, and while similar to 55-64 models in concept, implementation I different. Further changes in 65+ models, especially the twin lever Hyds models.