Home Forums General Discussion Technical Questions In-ground hydro: blown seal or jack

Inspected a possible blown seal or jack. The tank is totally empty, car is below floor level but doesn't seem to be low enough to be on the buffer( maybe it is). The pit is wet but not an entire 50 gallons worth. Planning to add enough oil to get it on pipe stands to inspect. I have encounter blown seal or just the opposite stick slip on hydro's. This would be a first blown out jack, but more tests need to be done to confirm.
If it the jack cylinder blown out; unsure if adding oil will lift the car. Otherwise we will hoist the car up ( no hoistway beam either). Mounting a beam or lift off the rails.
Does anyone have knowledge to share for diagnosing a blown out inground jack. Any special adapters to pressure test, or procedures?

First off, what is the age of the install? If it was installed before 1972 it probably has a single bottom cylinder. If it does it needs to be replaced wether it has a hole in the cylinder or not. I would use rail clamps and hoist the car to ascertain if the packing is the culprit. adding some type of blocking before getting under the car.

To diagnose an unknown loss of oil you need to perform a hydraulic leak down test. Your jackhead needs to be cleaned, pit can/scavenger pump needs to be empty and dry pumping unit drip pans need to be clean. Run the car up to the second floor and shut off power. Measure the oil in the tank and let the car sit for 30 minutes. If the car moves down inspect for oil on the jack head, vics, oil line, pumping unit, measure your oil in the tank. If all these check out then your oil is probably leaking in the ground either from the jack or an underground oil line.

Blown cylinders are common on older hydro units. If caught early it usually will not fail catastrophically, but it can so don't put anything you want to keep, like your body parts, in tight spots. It usually involves a small leak and doing a static/ relief test while monitoring the oil is the easiest. As Montana described is the static test, Confirm the oil is not leaking out of the head. putting oil absorbent pads around cylinder below the head is an easy method. Confirm the piping is not buried as it may be what's leaking. Keep the shut offs closed during the static test. If the unit was buffered for an extended time the packing may relax and siphon the tank dry, even with the shut offs closed. Guess how I know that. If oil is missing something leaked and if you cant see what leaked then it probably leaked under ground.

I was avoiding the single bottom cylinder debate. Its definitely from that time period. IMO any cylinder or pipe can corrode through if not properly encased with a sleeve or coating.
We can eliminate the piping because its just through the wall. Its the smallest cab I have ever seen for a commercial elevator, not much bigger than a residential. Should be able to reach in without complete entry and drop a pipe stand on the buffer. Really only two options the seal or the jack. Maybe a combination of both. That would be crappy to do the seal repair then find out its the jack once there is good pressure. The wetness from looking down on the cartop was more like a blown seal. After viewing the tank completely empty was a bit concerning, and put the jack in question. Hopefully I can get back to you guys with an update if they approve the repair.