I have this aluminum racing jack from harbour freight, and when I try to use it today it failed to work. I can pump the jack, but as soon as I raise the bar, the jack comes back down. I think I need to purge air, but who knows.

BTW, what kind of oil do I put into the jack reservoir?

Thanks in advance.

 

There should be a self bleeding screw

and you use hydraulic fluid to bleed it