Floor Jack Pump Piston Oring

[artbuc]

Re: Old Alltrade 2-1/4 ton floor jack...parts no longer available. A few years ago I replaced the pump piston oring with a used one I had which luckily was the right size, 116. Unfortunately I broke the backup ring and did not reinstall it. Now the pump piston is starting to leak again, not much, just enough to leave spots on the garage floor. I’m guessing the oring would have lasted longer if it had the backup ring.

Is it unusual for a 3/4” pump piston to have a 116 oring? I looked at a couple repair videos and both had 3/4” pistons with 208 orings.

I have new oring (actually a quad ring) coming along with split backup ring. Is the backup ring mostly to extend oring life or prevent catastrophic failure?

Thanks for your input.

 

[artbuc]

Re: Old Alltrade 2-1/4 ton floor jack...parts no longer available. A few years ago I replaced the pump piston oring with a used one I had which luckily was the right size, 116. Unfortunately I broke the backup ring and did not reinstall it. Now the pump piston is starting to leak again, not much, just enough to leave spots on the garage floor. I’m guessing the oring would have lasted longer if it had the backup ring.

Is it unusual for a 3/4” pump piston to have a 116 oring? I looked at a couple repair videos and both had 3/4” pistons with 208 orings.

I have new oring (actually a quad ring) coming along with split backup ring. Is the backup ring mostly to extend oring life or prevent catastrophic failure?

Thanks for your input.

I will answer my own question. Have read every article I can find. Looks like main purpose of backup ring is the extend oring life by eliminating extrusion, not to prevent a catastrophic failure. Need for backup rings depends on the obvious factors: clearances, pressure differential, oring hardness and temperature.

I could not install my new Teflon split backup ring. Not sure if original backup ring was thinner than standard or if it is just difficult to install with a quad ring vs an oring. Maybe if I had eased the backup ring square edge it would have been possible. Anyhow, I suspect the quad ring will still be working fine long after I am gone.

 

[HCRCnow]

Alltrade jacks are imported. The seals in them are metric. You probably have a 19mm pump piston. If you can not find them local, we offer a set, Oring and backup. This is a link.
These may not work on your jack. These are for Allied.
https://www.hcrcnow.com/shop/seal-kits/allied/13650