Quickjack Hydraulic Cylinder Won’t Retract

[Triumph1200]

So I bought a used Quickjack 3500, seller demonstrated but did not raise it to full height with a car on it, went up, went down, okay I’ll buy. My bad, when I put my light car on and raised it off the ground it would not come down, neither piston would retract. Switched lines side to side, pulled the couplers off (open to the air) and it’s not coming down. Got the car off with a couple of floor jacks so no problem there. Took it outside and tried to lower the jack by setting tractor forks on it and lifting the front wheels of the tractor off the ground, no go. More weight on the forks and then one then the other ramps came down rapidly spraying hydraulic fluid everywhere. Anybody have any ideas before I take the pistons to a hydraulic shop?

 

[matt_i]

Its possible that the piston rod is getting jammed into a bind (the rod is bent elastically relative to the guide bushing).

Its important that the cylinders "float" as far as being able to self-align somewhat. That can mean extra clearance in the end(s), spherical-joint(s) or Ive also seen T-shaped couplers with a matching T-slot.

If anything is extremely tight on either end of the cylinder mounts then you can get this phenomenon. Also look for the side of the cylinder going into hard contact with something as it pivots and the mechanism moves, which would also create the same type of bind condition.

If anything is screwed into the ports like a flow control or velocity fuse then that can also lead to flow-related issues but it seems unlikely those are the cause based on your description of a sudden release of fluid. Flow control would be a slow dribbling leak and the velocity fuse should be a check valve that can't be overcome short of outright destruction until its "reset" usually by the opposite flow.

 

[moab11]

did you check the relay on the pump if it was activating to release the pressure in the cylinders? If not then the system stays sealed as a safety precaution. Also the air cylinders need to be pressurized to the right amount to lower the jacks once the weight of the vehicle is off of them.

Disconnecting the hoses seals the lines, by forcing them down with the hoses disconnected you more than likely damaged multiple parts.

 

[Paycheck]

I assume you checked the air precharge on the cylinder? I had something like that happen once but it was because one of the lines got caught under one of the units.

 

[Triumph1200]

Yup, if it's not raised all the way up it will lower.

did you check the relay on the pump if it was activating to release the pressure in the cylinders? If not then the system stays sealed as a safety precaution. Also the air cylinders need to be pressurized to the right amount to lower the jacks once the weight of the vehicle is off of them.

Disconnecting the hoses seals the lines, by forcing them down with the hoses disconnected you more than likely damaged multiple parts.

 

[Triumph1200]

Cylinders were charged.

I assume you checked the air precharge on the cylinder? I had something like that happen once but it was because one of the lines got caught under one of the units.

 

[Triumph1200]

Nothing binding and nothing screwed into the ports

 

[Paycheck]

I would call Quickjack and see what they recommend.

 

[Triumph1200]

Been there done that, buy new cylinders.

I would call Quickjack and see what they recommend.

 

[nadogail]

When I worked as a Service Technician for a Hydraulic Shop, we saw problems like that in badly worn equipment.

Usually we rebuild those cylinders.