Hydraulic Jack Bleeding

[MitchW]

This doesn't really belong here but it doesn't seem to belong anywhere else either. At least it has to do with hydraulics and you can't work on your suspension without a jack.

I have a 3ton Allied (and a Sears 1.5ton) floor jack that needed some oil added. After I was done it still doesn't pump up right and I'm pretty sure that it needs to be bled. Anybody know how to do this or do I have to go out and buy yet another jack? The Sears was a cheapie so it probably is shot but the Allied was a moderately priced tool and I was hoping to get more than 5 years out of it.

[geh458]

It's easy. Here's what to do:

1. remove the plug that you probably used to add fluid
2. rotate the jack handle so that the jack is ready to lift
3. move the handle through 4 or 5 complete strokes
4. replace the plug removed in step 1

this procedure will bleed any air that might be in the jack.

[MitchW]

Thanks but im my case it seemed to require a different technique.

1. Extend the piston to full length (full height) and support it in that position and leave the valve in the closed (pump) position.
2. Remove the plug and alternate adding hydraulic fluid with small movements of the pump piston to remove air. Too much movement would spill fluid.
3. When no more fluid would go in and no bubbles are coming out replace the plug and lower the jack.

[rfx]

Both of the above methods of bleeding your jack are incorrect.

But before I explain a simple bleeding procedure keep in mind that there is a reason for your jack needing fluid in the first place. There is a leak somewhere. Usually the location of the leak is easy to locate. Thoroughly clean the jack. Set it on a piece of cardboard. Pump it a bunch of times (say 20 or more). Now let it sit there without moving it. Depending on the severity of the leak, the cardboard will show fluid within hours or a day or two. Now it's time to be a detective. Carefully examine the jack directly above where the cardboard show fuid. But don't be fooled. Sometimes the leak starts in a certain spot on the hydraulic unit, and then, because of the shape of the said unit and gravity, it runs to another spot where it finally falls on the cardboard. If you cleaned the jack real good, you'll be able to follow the fluid trail by examining it real closely with a flashlight.

Depending on how fast the leak is, you might be waisting your time filling the jack, and bleading the hydraulic unit of air. A profound leak will prevent the jack from operating.

Also, there are other reasons why your jack may not function correctly. Most jacks have an overload valve and a bypass valve. If there is dirt, or sludge, or any foreign particle in the hydualic unit, it could affect the operation of these valves. Are you sure you needed fuid in the first place. The inside of a hydraulic unit need to be surgically clean to have long life and function properly.

Always use hydraulic fluid. Other types of fluid will most likely ruin the seals inside the unit.

Now, as to the bleeding procedure for most jacks:

1. Fill the jack with hydraulic fluid to the proper level. It is possible to overfill the resevoir on some jacks depending on their design. Refer to the paperwork that came with the jack.

2. Leave the Filler Plug OFF. With the Release Valve OPEN (as if you were letting the jack come down), pump the handle about 20 times.

3. Put the Filler Plug ON. CLOSE the Release Valve. Try to jack up the unit. If it works, you are on the right path. Note....I would do steps 1, 2, and 3 a few times.

NOTE: Never raise the Lifting Arm of the jack manually. This will suck air into the hydualic unit. Also, when traveling with the jack in a vehicle, alway have the Release Valve OPEN, and the jack in an upright posistion (take the Handle off if necessary. This can suck air into the hydualic unit when you go over bumps in the road.

If this did not fix your problem, there is most likely an internal problem within the hydraulic unit. If the jack is not an expensive one, don't bother having it repaired. It would be cheaper to go buy another one.

CAUTION...Any jack, leaking or not, can have a catastrophic failure while under a load. ALWAYS USE JACK STANDS. ALWAYS USE JACK STANDS. ALWAYS USE JACK STANDS.

[MitchW]

Yep, I'm sure it's leaking. We'll see how long the refill and bleeding lasts and of course I always (x10) use my jack stands. Years in the gym still haven't made me strong enough to bench press even the lightest Alfa

[rfx]

Mitch,

Please note that I have revised my reply by adding some very important info in the bleeding procedure. Make sure you read it again.

Good Luck,
Rich

[Alfissimo Int.]

Thank you. This method is correct and worked on my jack today which was un able to jack to it's full length, only got halfway after 15 years of use.
Bled as mentioned and all works fine now.
Ciao!
jason

Quote:

Originally Posted by rfx Both of the above methods of bleeding your jack are incorrect. But before I explain a simple bleeding procedure keep in mind that there is a reason for your jack needing fluid in the first place. There is a leak somewhere. Usually the location of the leak is easy to locate. Thoroughly clean the jack. Set it on a piece of cardboard. Pump it a bunch of times (say 20 or more). Now let it sit there without moving it. Depending on the severity of the leak, the cardboard will show fluid within hours or a day or two. Now it's time to be a detective. Carefully examine the jack directly above where the cardboard show fuid. But don't be fooled. Sometimes the leak starts in a certain spot on the hydraulic unit, and then, because of the shape of the said unit and gravity, it runs to another spot where it finally falls on the cardboard. If you cleaned the jack real good, you'll be able to follow the fluid trail by examining it real closely with a flashlight. Depending on how fast the leak is, you might be waisting your time filling the jack, and bleading the hydraulic unit of air. A profound leak will prevent the jack from operating. Also, there are other reasons why your jack may not function correctly. Most jacks have an overload valve and a bypass valve. If there is dirt, or sludge, or any foreign particle in the hydualic unit, it could affect the operation of these valves. Are you sure you needed fuid in the first place. The inside of a hydraulic unit need to be surgically clean to have long life and function properly. Always use hydraulic fluid. Other types of fluid will most likely ruin the seals inside the unit. Now, as to the bleeding procedure for most jacks: 1. Fill the jack with hydraulic fluid to the proper level. It is possible to overfill the resevoir on some jacks depending on their design. Refer to the paperwork that came with the jack. 2. Leave the Filler Plug OFF. With the Release Valve OPEN (as if you were letting the jack come down), pump the handle about 20 times. 3. Put the Filler Plug ON. CLOSE the Release Valve. Try to jack up the unit. If it works, you are on the right path. Note....I would do steps 1, 2, and 3 a few times. NOTE: Never raise the Lifting Arm of the jack manually. This will suck air into the hydualic unit. Also, when traveling with the jack in a vehicle, alway have the Release Valve OPEN, and the jack in an upright posistion (take the Handle off if necessary. This can suck air into the hydualic unit when you go over bumps in the road. If this did not fix your problem, there is most likely an internal problem within the hydraulic unit. If the jack is not an expensive one, don't bother having it repaired. It would be cheaper to go buy another one. CAUTION...Any jack, leaking or not, can have a catastrophic failure while under a load. ALWAYS USE JACK STANDS. ALWAYS USE JACK STANDS. ALWAYS USE JACK STANDS.