The Stovebolt Site Forums The Parking Lot Big Bolts Brake help-Trouble shooting 57 6100

I am new to the old hydravac system so bear with me. Pedal in my 57 6100 goes to the floor. It was like this when I bought it. I have ran through the bleeding sequence with both bleeders on hydravac then left rear right rear left front fright front. If I pump really fast I can get enough pedal to hold about 2” off the floor but that’s it. One thing I noticed if I pump them up real good them let off and pull the MC lid off it will sometimes spray fluid up out of the MC. Wasn’t sure if that would be normal? Also the brake fluid will be white, like full of air. What would be a good place to start to try to see if it’s the MC, Hydravac or the dummy working on it. Also, if I would give up and put a newer style power brake setup, is there still a way to operate the two speed rear ended without the hydravac.
FYI the truck don’t run at the moment, waiting on a couple parts to come in before I can drop the motor in.

Hy Wvgearhead, have you adjusted all the brakes up to where they should be?

There should be a check valve in the port of the master cylinder that would hold some pressure in the system when you pump it up. Drum brakes have it, discs do not. If the brakes are not adjusted and that valve is working, you should only have to pump it up once and then the pedal should be "normal". After the brakes sit a while, you would have to pump them up again. Sounds to me like that check valve is not working and the adjustment is off like 3B suggested. I don't know of a way to replace the check valve, I think that would be one for a rebuilder. Maybe someone here knows how to do it.

I would suggest doing the adjustments on all wheels as a starting point.

No I haven’t adjusted them. I will give it a go and see what happens. I will let you know what I find.

The hyrovac does not control the rear axle 2 speed, if you have a vacume reservoir that would be the only thing in common. While I was rebuilding the brake system on my 5700 I bypassed the hydrovac, I am now using manual brakes with all six wheel cylinders and the master cylinder having rebuild kits and all new cupro-nickel lines and new rubber hoses. You have to adjust the shoes very close, mine stops very well with a solid pedal and no leaks. I doubt it will ever be loaded to 16000 lbs. so for now I'm happy with it.