Jpage1w
New member
I have a Napa 791-6402a jack. After allowing my son to use my jack it would no longer function properly. I diagnosed it as he kept turning the release past where he needed allowing the check ball to escape and be gone forever. But it took me completely disassembling the hydraulic unit to find the problem, I replaced the ball and thought all was good until went to use the jack. Now it lifts until it's just about to lift the tire off the ground, at 225lbs I almost have to hang from the handle to get any lift. It gets gets extremely hard to jack. It doesn't leak down but the handle feels to be holding pressure as it rises with a bit of force. I am thinking it's in the check valve. Any other suggestions or anything I could be missing? I did count the turns on the safety valve before disassembly btw