[dsraven]

to bleed a hydravac you need to first bleed the firewall mounted master cyl at the line fittings. then bleed the bleeder screw on the hydravac unit and if possible use a clear tubing so you can see if there are bubbles coming or not be patient as this can take a lot of time to get the air bubbles from the firewall master all the way down to the frame mounted unit. you're gonna need a good supply of brake fluid. once you are absolutely sure there is no more bubbles from the first part then tighten that bleeder screw and go to the furthest away wheel and do that one next. a pop bottle partially filled with the clear line set into the brake fluid and held there so it can't come above the fluid in the bottle is a decent way to bleed them so no air gets in. a tight fit on the bleeder screw to the tubing is also good and don't back the bleeder screw out a whole bunch thinking you will get more flow because that also leaks air into thee system when the brake pedal is released.some guys I know will try the reverse bleeding method where presure fed brake fluid is forced backwards through the system from the bleeder screws. i personally prefer the old fashioned pedal pump method. also ensure you have a helper to keep an eye on the master cylinder level so you don't suck air from that end. you gotta start over