Forward 2 post lift dilemma

[cabinover]

Hi all, having a problem with my lift and want your input. Forward 10K 2 post lift. Up until last week it'd been fine. Raised the arms to hang a 200# object and blew the 1/4" vent line at the opposing cylinder. Repaired and immediately blew it again. (BTW, this makes a terrible mess on motorcycles, floors, and anything else in the way)

Now my thought was how did that fluid get on the other side of the piston? Disconnected vent line and ran both cylinders into containers, drew all fluid out of them.

Refilled reservoir and attempted to raise my Traverse. No go. Will lift to bottom of car but won't budge the car. Also, the lift slowly drops. I've pulled the return valve thinking maybe a piece of **** stuck in it, clean as can be. Today the other side of the pistons are full of oil again.

How can two pistons lose their seals at the same time? I've never even come close to having 10K on this lift. I can't imagine this happening to both at once but it's the only thing that makes sense. Appreciate any thoughts on this.

 

[joel_400]

I would believe they are only one way cylinders on a lift, since gravity does the work in the down position. Maybe since the one side was bad the second side was doing too much work trying to lift the car so it decided to go on strike as well! Haha either way I would believe that there shouldn't be much, if any fluid on the other side of the piston. Personally I'd try to locate seal kits for the cylinders and try that first. If you can't find the seal kits and you're lucky enough to have a good hydraulic shop nearby, like I do, you may not have to buy the seal kits. I've taken them seals and such and they will sometimes make a kit out of their stock bins. Good luck!
Joel

 

[cabinover]

I would believe they are only one way cylinders on a lift, since gravity does the work in the down position. Maybe since the one side was bad the second side was doing too much work trying to lift the car so it decided to go on strike as well! Haha either way I would believe that there shouldn't be much, if any fluid on the other side of the piston. Personally I'd try to locate seal kits for the cylinders and try that first. If you can't find the seal kits and you're lucky enough to have a good hydraulic shop nearby, like I do, you may not have to buy the seal kits. I've taken them seals and such and they will sometimes make a kit out of their stock bins. Good luck!
Joel

That is possible one side being weak. Glad to see that my thinking is on the right track though. I'll order kits, they aren't that expensive, something like $50.

 

[TurnipTruck]

You mentioned a vent line. That makes me think you have an I or an F model, with pull rams that retract to lift, instead of push rams that extend to lift. Blowing the vent line off would be a sign of major internal seal damage or even a piston failure.

 

[Drill Sergeant Arc]

I’ve got a early 1980’s Benwil 9000 that has a vent on the top of the cylinder. This allows the top of the ram piston (no pressure side) to bleed air in and out of the top. When a car is on it it cannot reach maximum height but when I tried what you did it went to the top and shot out HF. When I dropped it back down it has worked as normal since.

If yours isn’t vented to the outside like mine and instead goes through a line to the reservoir there may be a check valve stuck open and it’s by passing fluid.

 

[gregs]

My Eagle 2 post just has a vent fitting on each cylinder. When the seals cracked and disengrated it blew oil out and made a mess. I ordered parts and rebuilt both at the same time. The other was on the verge of doing the same. When you think about it, they are both doing the same thing, the same time, and aging at the same rate so it would be normal for both to fail very close to each other.

 

[cabinover]

Thank you for all of the replies folks. I spoke with a Forward dealer today from Ashland, NH and he said I had a bad piston seal allowing fluid to bypass and get to the other side. Just one piston leaking will load fluid into both piston top sides and make a mess. I will do both pistons and be back in business, no sense doing just one even if it is fine. Parts are not that expensive but piece of mind is priceless. Thanks again, hope I can return the favor someday!