Originally Posted by leegreen (Post 9298534)

Any hydrovac or OEM 1958 bendix hydrovac?

newer medium duty cabover trucks often have them

or you might find an old one and a rebuild kit on ebay

Its probably cheaper to buy an aftermarket kit to put a dual master and booster where the stock master is

Originally Posted by 58ApacheGuy (Post 9298857)

Thanks. Have been considering this resolution. Problem is with frame mounted master cylinder, if I mount the vacuum booster combo, I'd either have to convert to automatic transmission, or convert manual clutch to hydraulic clutch, which I haven't even begun to research.

Originally Posted by dsraven (Post 9298982)

Forgive me if I'm wrong here, but the hydrovac boosters I remember had a master cyl that was foot pedal operated and that sent a signal to the hydrovac booster mounted somewhere else and it also has master cylinder on it that operates the brakes. Really, a hydrovac from a newer truck should be able to be serviced on your old truck. Just do a bore size comparo and go from there. Maybe also run a vacuum reservoir tank with one way valves so you don't run out of vacuum. Really though, if using the brakes, the throttle should be closed causing a higher vacuum. It depends on rpm then as to what vacuum you actually see.

Originally Posted by dsraven (Post 9300751)

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 top of the hydravac unit that looks like it is oposite of the supply line that comes from the master cyl on the firewall 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 and also keep checking the master cylinder fluid level. once you are absolutely sure there is no more bubbles from the first part then tighten that bleeder screw and go to the next bleeder screw on the unit which is close to the outlet where the line leaves the booster and heads off to the wheels. then when thats all good clean fluid with no bubbles go to the furthest away wheel and do that one next. a one man bleeder is handy for this as sometimes the "pedal man" and the "bleeder man" can get out of sync and that can allow air to enter. 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