Home Forums General Discussion Technical Questions Telescopic Jacks

Having problems with twin telescope jacks. The jack on the right works great. When I run the car the jack on the left side only pushes out the big cylinder until you get high enough and it hits it's stop ring. The small cylinder pushes out if you continue to run the car. Once you stop running the car the small cylinder sinks back in until it's collapsed back into the bigger cylinder. The small one doesn't seem to hold the pressure in. I have no leaks, bled the jack a thousand times,the jack seemail to always havery air in it, changed the seals in it twice, even tried syncing the jacks a bunch a times also. I'm at a loss. Checked the piping in the pit also, piping is even feeding both Jack's at the same time. Any help is appriciated.

I used to work for tk in construction and we had the same problem with a jack like that that was brand new from the factory. It came missing a type of check valve that divides the pressure to make each jack move at the same time. That's been almost 10 years ago so I don't remember what it looked like. I just remember we had to chain fall both plungers out to get to it. I'm sure that same valve is what's causing your issue.

Correction: these valves make each plunger move at the same time. They are located at the bottom and inside of each jack.

Correction: these valves make each plunger move at the same time. They are located at the bottom and inside of each jack.

Are your jacks made by Dover/TKE? If they are the as I would second JcJmowery. With the added info that these check valves do go bad or it could be a internal seal leaking which you obviously won't see. Either way you would have to remove both pistons to get at either one and you might as well replace both if you go to the trouble of taking them apart.

I have mainly had issues with the Dover/TKE style telescopic cylinders but it is my understanding that other manufacturers use a similar design with the check valves as I believe my company replaced a set of check valves on an some OLS telescopic jacks as well once.

And if I remember right, the check valve is attached to the bottom of the larger plunger

If it is dover/tke, look up vertical express website under manuals. They've got a great write up on how to replace and part #'s.

The large plunger will have a seal at the bottom. It sounds like it is leaking. Normally as the large stage goes up the oil above the seal in the area between the bottom seal and the head will be forced inside the large plunger and push up the small stage at the same time. This works because the area of oil between the outside of the large plunger and casing is equal to the area below the small stage. Over time this will get out of synch. That is why there is a "check" valve in the bottom of the large stage. When lowered all the way down, it allows the small plunger to equalize back to the bottom. You will need to pull the large stage out and inspect / change the bottom seal. Good luck!

We pulled out the large stage and replaced the seals at the bottom. Worked like a charm. Thanks for all the help guys!