Help w/ AFF 550 Floor Jack

[JD Thomas]

I got a used AFF 550 2-ton jack several years ago, and it's always worked fine, but recently just stopped being able to lift a load. It would lift about halfway, then leak down a bit. There no actual leaking of oil anywhere though. First thing was to check the oil level. When I unscrewed the fill hole there seemed to be NONE in there at all. I figured that must be it, so I filled it (in the released position, left a little air space, pumped several times to bleed out any air bubbles), put a new rubber gasket on the screw, and screwed it back in. Still wouldn't lift.

So after reading a bunch here, I checked the overload. There is just one main screw, with an extending needle tip at the end, and a spring below that. I fully tightened down the screw, and then backed it off about a 1/2 turn. Tried again, still won't lift.

Next, I fully unscrewed the release valve. There was a rubber gasket all the way inside. I pulled it out, it seems fine (supple, no tears), put everything back together, still no dice. It's going about halfway up - it seems fine taking the weight of the car off the shocks, but will hold there, and won't continue to lift the tires off the ground, even though I'm pumping. I put some some soapy water around the oil fill screw, the overload screw, and the release valve to see if air was being forced out somewhere when I pump, but no bubbles, so...

Does this indicate it must be something inside the main piston?

 

[Hiball]

Does this indicate it must be something inside the main piston?

I'd say that would be a good place to look, Unfortunately 99% of the time it comes down to replacing soft parts as they age, Its just part of it.

 

[JD Thomas]

Thanks for the reply Hiball. Actually, before tearing into it, I thought to retighten the overload screw all the way, and give it another shot. Lo and behold, it lifted fine, like it always had. Don't know what the deal was, maybe it was airbound, and my fiddling with it finally cleared it all out. I'm kinda spooked now though - I can imagine the car suddenly crashing down before I have the jack stands in the correct place, and some part of the undercarriage getting mangled. I think I should probably go ahead and get a new jack.