Bleeding a Hydraulic System?

Posted in: , on 7. Aug. 2009 - 06:34

I have an old Lull forklift and ran it low on hydraulic oil and got air into the system. How do I get it out?

Oil In A Hydraulic System

Posted on 7. Aug. 2009 - 02:18
Quote Originally Posted by tmccradyView Post
I have an old Lull forklift and ran it low on hydraulic oil and got air into the system. How do I get it out?



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Please before you get your self or someone else injured or killed from an oil penetration injury-do absolutely nothing!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

DO NOT CRACK OPEN/LOOSEN A HOSE FITTING THE SLIGHTEST AMOUNT AS INJURY WILL RESULT FROM UNCONTROLLED OIL PRESSURE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

First- did you find the leak? It could be a number of things;

1. leaking valve spool seals

2. leaking pump shaft seal

3. blown hose.

4. weeping hoses-must be changed, hose with a brittle hose carcass/exposed wire braid-must be replaced.

a. a leaking bad suction line

b. a bad pressure hose line from the pump to the valve bodies

5. blown o-ring seal in a hose flange fittting.

Second- you must do this and only this;

start your forklift and simply let it idle and only idle please!!!!

If you have operated it with low oil the operatiion of the forklift will be spongy because of air in the cylinders and bleeding them is out of the question as it is a good way to be injured or killed from an oil impact injury. slowly cycling the cylinders is the only safe way to remove any air bubbles and it is a long process as the air in the system that is trapped wants to compress and will require time and patience to allow it to escape.

please change the hydraulic oil filters if you have not already done so as the filter paper has most likely been punctured b the air in the system.

leon