I replaced the handle pivot pin on my jack. Didn't know that was all that kept the piston in. So the piston popped out while I was machining a new pin. I lost all or most of the hydraulic oil.
I don't have the manual, but managed to refill the pump. Now it will raise with one pump but lowers on the up stroke. So I assume air is trapped in the system somewhere??
Tried bleeding but not sure how to do it??
It is a Dayton 4YX96.
Any help? Grainger doesn't have a online manual for it.
Those pallet jack cylinders shouldn't need bleeding..The ones that i have worked on will bleed themselves..the resevoir is open to the atmosphere, so that doesn't seem to be your problem..
It sounds like you might have some crap inside the system which is not allowing the steel ball to seat properly..
the steel ball is designed to shut off a port on the down stroke of your handle..
I think you lost a steel ball valve, entirely. Maybe 2, but at least 1 or mebbe just a spring return.
Most have 2, some have 3 ball valves. Intake, pressure, and some have a ball as the release valve, others use a needle valve.
Here's an animation of how a jack works. It is the same as how yours works.