The Stovebolt Site Forums The Shop Area Engine Shop Brake Lock-up Problems: Don't Try This At Home

I have a 1954 Chevy short Bus (1 1/2 -2 ton) that is giving me problems with the brakes locking up.

I bought the old girl on EBay. Flew from Florida to Montana to buy it with my teenage son. Previous owner said it was in great shape and would make the trip.

ALL LIES. Brakes were very weak (3 pumps to stop if you were lucky), dry-rotted tires, no lights. Anyway, I found 4 bias tires, replaced the master cylinder/lights by the roadside, changed oil, etc. Got a brake pedal back. I would have flown home and had it shipped, but the previous owner did not want to get involved with shipping it.

Soon after, while trying to drive an old bus home, my brakes locked up so badly that the rear drivers side brake turned cherry red. So hot, it smoked for an hour in the dark, out in the middle of nowhere.

FYI-don't attempt a drive like this in an old relic you bought on EBay unless you are both a fool and a glutton for punishment.

A small shop in Montana now has my bus. The rear wheel cylinders were rebuilt, rear shoes replaced, etc. Brakes seemed fine.

The mechanic having checked over the bus for me in advance, I drove out to Montana with my family and all of my tools to give it another go.

I took it for another drive after the brake work, thinking that the problem was remedied.
More problems, the fuel line had a home in it, there were no front shocks (in fact one front shock frame mount was missing). Anyway, changed fan belt, thermostat, fuel line, heater hoses, fuel filter, flushed radiator, etc.

Took it for another test drive. Lousy brakes started intermittently locking up again. The brake pedal became rock hard, and the rear brakes would not release. Brake light quit working (wasn't fuse).

I suspect that the power brake assist unit (hydrovac?) is causing the problem with the brakes. Has anyone out there experienced this? The shop that worked on my brakes adjusted something underneath the truck that made the brakes loosen up so the truck would actually move again. Afraid to attempt a another attempt at driving it home, I decided to come home with my tail between my legs and have it shipped home by truck. It should be picked up and shipped to Florida in about a week.

If it's the power assist, can these be rebuilt without too much difficulty? I am a halfway decent mechanic, but never tried to fix one. Is it better to try and upgrade this unit?

I want to drive this bus a lot, and want to make it stop as well as possible. I am looking to see if a better, dual master cylinder is available, a front disc brake conversion, etc.

Any ideas would be greatly appreciated. Thanks for sharing my dreadful story.

George
http://www.oldbus.us

George:
By the time you get back to Florida the bus should be completely restored.
Actually a good Samaritan will be by shortly to give you some expert advice on this. My advice (no charge) is to rent a trailer and truck and pull that bus back to Florida.

It sounds like the master cylinder rod attaching bolt is turned wrong. That bolt has a 3/4 head on one side and a 9/16(1/2?) head with a cotter key, on the other side. The bolt is made like a cam and you loosen the small nut and turn the big bolt until the brake pedal arm has about a 1/8 inch play, before it starts pressing on the master cylinder. What you describe is the master cylinder never fully releasing the fluid and after a few uses it has the brakes pumped up and won't let the fluid return to the master. Most people don't know that the bolt has the cam shoulder made on it.

Thanks a lot for the replies, especially that last one from 46 Chev. I changed the Master myself, trying to count the threads meticulously to get it the same as when I removed it. I didn't check for free play. I'll bet that's it.

The truck should be back soon with my bus, and I will check that adjustment. Thanks a bunch

And my friends think I'm insane... :crazy:

I agree w. 46Chev. It sounds exactly like the issue you'd get with the MC not retracting far enough to release the system pressure. Once that happens you'll just get a harder pedal. I was having issues getting mine set & found it was easier to set the eliptic bolt mentioned above while someone slowly depressed and released the pedal so I could see if it was binding up on the return. Also a good idea to replace the return spring if you haven't allready.

You can check the function of the HydroVac by putting your foot on the pedal and starting the motor. As soon as you get vacum you should feel the pedal go down a bit as the HydroVac kicks in. You'll also want to check all the air lines to make sure you dont have a vac leak. Odds are the HydroVac will need a rebuild, the good news is there are rebuild kits available, and if you dont feel up to tackling it there's an outfit, I think in PA, that does them. My local NAPA had all the info in thier books about who to send it to.

As for function, I have rebuilt the entire brake system on my 2-ton dump and it stops really well for something it's size, having a funtional Hydrovac makes a huge difference.
There's also a couple folks on here that have converted to HydroBoost, same concept but uses pressure from a power steering pump instead of engine vacum.