I have a 1983 Bronco, 302, c6 transmission, vacuum assisted power disc. So recently within the last month or so i started to notice the brake pedal would start to move towards the floor after coming to a complete stop. I immediately thought that maybe a brake cylinder was leaking, or the master cylinder was shot. The fluid level never decreased... its still full fluid wise. The other day i was coming home and the brake pedal just went straight to the floor and I could barely stop, and when i did stop it was a big jolt like the brakes were locking up. Now i have no brakes at all you just press it and it goes straight to the floor...stopping sometimes but mostly no brakes what so ever. I started to think it was a vacuum issue, because with the truck off, there is plenty of resistance in the brake pedal, but as soon as you turn it on...nothing... I do need to replace a gasket on my carb and since the booster pulls vacuum from the manifold....i thought somehow maybe it was a culprit. But really i have no idea, and i don't wanna go buy a new m/c or brake booster if i can just finally do the work on the carb and the vacuum leak issue resolves the brake thing.

help!

thanks,

aaron.

 

Nope. When the booster is working, it magnifies your effort. If the booster is NOT working, then the brake pedal would be just as hard to push with the engine ON, as it was with the engine OFF.

In the last 2 months or so, I posted the brake booster test procedure. But the booster is not your problem from what you describe.

If you are losing NO, and I mean none at all, brake fluid due to a leak, then most likely your master cylinder is internally bypassing. Worn out internal seals that flip over under enough pressure.

But be sure that you don't have a leak somewhere first. And that you don't have a brake hose that is ballooning up under pressure. Check both front brake hoses, and check the rear hose that goes from frame to axle. If there are big cracks in the rubber, and reinforcing cord visible, they should be replaced, even if they don't turn out to be the problem.

 

I agree with Torky2. Nine times out of ten, with a brake pedal that goes to the floor it is going to be the MC.

Jim