Bleeding hydraulic cylinder on auto lift?

Going to replace a pump for a friend of mine on a 7,000lb Benwil lift.

Is there anything special that needs to be done to bleed the cylinders? Or just fill the resivior, and raise and lower the lift a few times with nothing on it?

Not sure. Check cylinders for top-side bleeder screws, that's the best clue.

I suspect the cylinders bottom out (single acting) and push nearly all the oil back into the reservoir.

So, as you state, a couple times full up and back down should get it done. Check under load with a vehicle...the lifting is synchronized with chains that attach to both sides, so not 100% sure how you'd detect a soft cylinder...possibly a lot more audible "load" on the electric motor.

If there was any bleeding capability, again probably at or near the rod-gland on the cylinder or a very remote possibility of thru the far end of the piston-rod, the procedure would probably raise full height and wait awhile for air to consolidate at the top...bleed both sides, then let down.

Follow manual instructions if available...I know Benwil was sued out of business, but other companies have picked up the spare parts business.

The good news is this is an older single cylinder system, one cylinder on the pump leg and a chain connecting the other side. Just don't want it squishy.

Yes, this is a single acting cylinder being fed from the bottom. It is the lowest point in the system by a good 4 feet.

Also, I should ask (before I stand under a car on this thing), why were they sued out of business? Patent infringement? Inept JiffyLube tech that hurt himself and got a superlawyer to win some rediculous lawsuit? Or was there legit problems with this unit? This is an older 2 post, 7,000lb lift with the chain on the bottom diamond plate cover you have to drive over.

I've always like the Benwil lifts, they are very sturdy, solid lifts that don't sway around like the Rotary lifts and some others.

Don't have the details on what exactly happened...probably some goofball picking up the front end of the car on 1 or 2 legs, not having both the safety latches engaged on both sides (sometimes they don't pick up perfectly identical side-to-side and need 1/4" more upward motion before they will, pins not latched in the spacer-arms. Who knows.

They seem to be good lifts though, although the chainwheels will wear out the inner bushings over a long period of time and possibly not the most regular lubrication schedule.

If you stand under it, in proper condition, the hydraulics are doing no work, it is all held by mechanical safety catches (a linear ratchet of sorts).

I am not positively sure,but with the single acting cylinder I don't think it will have a bleed screw on it.If you raise it completely and lower completely once or twice it should purge all air into resevoir.Listen if at all possible to cylinder and then resevoir.You may be able to tell if there is air in the cylinder as it has a different sound that it makes unlike when there is no air and it sounds smooth and powerfull.Look for bleeders and if there are none just do the above like Matt also said.

I can'tsay on that exact lift but in general just fill it with oil and cycle it.