8n lift problems

[rbtklee]

I just bought an 8n and the guy said he rebuilt the hydraulic pump, but it will not lift anything. It will go up with no weight on it, but then it won"t go down. I have cleaned out the entire system and changed the oil twice, but nothing changes. Am I missing something, or do I need to rebuild the pump again? Any help is truly appreciated.

 

[souNdguy]

Put a load on the lift, pull the dipstick inspection cover, lift the lift handle.. look for squirts and sprays or swirls in the oil..

post back what you see.

If you are slightly familiar with the system i reccomend you chaining down the lift arms to the axles, and removingthe test port from the pump base and getting a pressure gauge ( 3000 psi ) with an orb fitting, and threading it into the pump base,a nd then lift the lift, and see what pressure you develop.. should get 1500-1700 psi.. by the time the relief is open and venting..



soundguy

 

[JMOR]

Look at my diagram.
In order for the lift arms to drop (lower) the fluid contained (colored area) must be released. That release path is the Exhaust Control Valve. It must Open.
It may be stuck or clogged with trash, or not moving due to mechanical linkage problems. You can reach in via the round port on the right side of tractor and try to move this valve manually to see if it will drop. Don't put hand it there with tractor running.

To prove that it is hydraulically locked in up (as say opposed to a mechanical lock up), protect eyes from spewing oil and remove the test port plug and the lift will drop. It will be a messy pint of oil!

 

[Anonymous-0]

JMOR, that is a neat drawing. Even I can understand the lift system from that.

 

[JMOR]

(quoted from post at 16:54:52 03/19/08) JMOR, that is a neat drawing. Even I can understand the lift system from that.

Thanks! I'm a real visual kind of person, so I spent a ridiculous amount of time figuring it out, so I had to document it. To some it may be useless, but to me it certainly tells me where to look/not look, depending on symptom, such as ' won't lower', or 'lowers once up', but won't lift load', 'leaks down over time', etc.

 

[rbtklee]

yes, once I release plug, the lift will go down.

 

[JMOR]

Then, referring back to my sketch, clearly there is an obstruction to oil flow somewhere between the test port and the outlet of the Exhaust Control Valve. I would bet on stuck Ex Ctrl Valve vs a passage.
You need to try to move that valve manually thru the round side port (the one with the dip stick in it).

 

[Hobo,NC]

When I have a pump out I hold the test port up and fill the test port with fluid and hold the control linkage in,,, I then release the linkage to see if the pump will dump the fluid,,, if not then the exhaust passage in the pump is stopped up....

 

[rbtklee]

I will try that tomorrow, thanks everyone for the information. I will probably pick your brains on other stuff later on.