The Stovebolt Site Forums The Shop Area General Truck Talk Break Booster Blowout

Any tips on troubleshooting the break booster on a 65' C20. The booster went out when I was pulling into the school parking lot this morning causing me to run over the sidewalk. The breaks still work put the pedal sinks way down like they do on my non-power break 66'. I checked the vacuum line and it still seems strong although I didn't have much time to investigate further. Any advise would be appreciated.

Start by checking all the wheel cylinders for leaks. It sounds like you've lost pressure to half the system for some reason, or one chamber of the master cylinder has failed. A bad booster would result in a hissing noise, a very hard pedal, and possibly a rough-running engine if the vacuum leak was bad enough.

The pedal going over halfway to the floor is a dead giveaway that one end of the brake system has lost pressure. That's how it's supposed to work.
Jerry

It also depends on the type of booster. I thought that the Midland Hydrovac types were used in the 60s but Im not positive. These can blow a seal inside and basically all the fluid gets dumped into the vaccuum chamber, hence no fluid getting to the wheel cylinders.

Just a thought.

Jeff

Thanks for the replies. As for the seal on the booster, I am fairly sure that no fluid actually is contained inside the booster itself, just on the master cylinder attached to it. I guess it is possible that a seal on the rear of the master cylinder went out and it leaked inside of the booster so I will check that out. Anyways thanks for the replies, I won't be able to check it out for another two hours yet so I will post back when I have more info. Wish me luck on my trip back home, I hope the breaks hold up a little while longer, they were always sensitive anyway.

Well, it is defiantly a leak somewhere. The master cylinder, which I had recently filled, was dry as a bone. I slowly limped over to the local auto parts store and filled it up, thank god for the super speeds of granny-low with a 4.11 rear end. From what I can tell the front left wheel looked a little wet on the inside. I guess the next time that I get a break I will check all the cylinders. Really, it needs a whole break job, everything is ancient and the lines are getting quite rusty. Also the crushed rear right break line acquired while pulling old fence wire out of the ground, is probably not healthy

If you have the master that attaches to the booster then it is not the Midland Hydrovac type. They were a remote unit so the chances of a seal blowing in your booster is pretty slim.

Jeff