Hydraulic jack problem

[aidank]

I have an ordinary hydraulic bottle jack, it’s a 15ton model, lifts 5inch or thereabouts. I hadn’t used it in a while so tried to use it today lifting 4ton.
I got all the air out of the jack first by extending fully and then turning upside down and lowering.

put jack under load and off I went and jacked up. Got 4inch extended and jack began to come down.

Paused for a min and began lifting again and all was good, I got the jack up high enough and stopped.

watched for 2 min and then jack suddenly begin to slide down. Slides down 10mm and stop and hold and there we stay. The 4 ton still on it by the way

I repeated the above and same thing happened.

jack hasn’t been used in years but was stored standing up correctly.

Plenty hydraulic fluid in it.

any ideas

 

[Hiball]

I guess I’m not sure what turning it upside down to bleed the unit is accomplishing, seems counter productive to me.

1. With the bottle jack on its bottom, Crack the fill plug if it’s a threaded bolt.

2. Release in the Release position, 10-12 pumps, Check oil with the jack on its base and upright. Add till it trickles out the fill hole.

3. Close the release and cycle the jack to full extension and open the release and depress the ram manually.

4. Use the jack under load, once the load is up, depress the handle to the down position and watch for any movement. If the Handle starts to rise as the load drops, It’s a valve issue and is pressure is back feeding into the pump cylinder.

 

[aidank]

I guess I’m not sure what turning it upside down to bleed the unit is accomplishing, seems counter productive to me.

1. With the bottle jack on its bottom, Crack the fill plug if it’s a threaded bolt.

2. Release in the Release position, 10-12 pumps, Check oil with the jack on its base and upright. Add till it trickles out the fill hole.

3. Close the release and cycle the jack to full extension and open the release and depress the ram manually.

4. Use the jack under load, once the load is up, depress the handle to the down position and watch for any movement. If the Handle starts to rise as the load drops, It’s a valve issue and is pressure is back feeding into the pump cylinder.

The reason for turning upside down is so that the air in the piston chamber goes to the valve first and exits from the piston chamber into the reservoir when you compress the jack piston. Hope that make sense

 

[Hiball]

The reason for turning upside down is so that the air in the piston chamber goes to the valve first and exits from the piston chamber into the reservoir when you compress the jack piston. Hope that make sense

It does not make sense, but that’s Ok. Pumping the handle with the release in the release position purges all Air from the pump piston/valves/release vein, With the release in the lift position it clears the main cylinder via the release port into the reservoir upon cycling the Main ram up and down.

If your jack, upon releasing is allowing oil into the “Valve” system you have issues. The upper ball/cartridge valve should not allow oil back into the pump cylinder. The correct path for the Oil when the Main ram is depressed is Cylinder -> Release port -> Reservoir.

When you invert the jack, All the oil rushes to the top end and empties the intake ports at the base of the reservoir. When you flip it back over, You guessed it.