At 12:00 AM 2/4/02, Scott C wrote:
>Looking for some insight here.... Am I on the right track?
> 1) '81 5-sp, 119k miles
> 2) Firm pedal initially with somewhat spongy travel when pressed hard.
> 3) After one or two fast stops (60-0) the brakes fade considerably
>Here's what's been done:
> 1) 10k ago the pads were changed.... rotors were not done
> 2) Brake fluid flushed 500 miles ago with ATE Blue. I noticed considerable junk and rust flakes being cleared during the process.
> 3) Bleeders were changed because originals were rusted too much to pass fluid during flushing in #2.
>Future Plans:
> 1) Rebuild Calipers
> 2) Replace Rotors and pads
> 3) Install braided steel lines
>Am I on the right track here?
>Could it be the booster?
>What symptoms are exhibited when a brake booster fails?

A quick check of the booster:
- With the engine off, press and release the brake pedal ten times. This bleeds off any stored vacuum.
- Release the pedal, wait about thirty seconds, and try the pedal for feel - that is, push it and see how firm the pedal is. This is the unboosted feel. If the pedal is spongy, there is a problem - most likely air in the system, but possibly a bad line, or bad master cylinder.
Release the pedal, and then press it very lightly. If the pedal slowly sinks, time for a new master cylinder.
Release, then press and firmly hold the pedal, and crank the engine. If the booster is working, the pedal will sink under your foot and will feel slightly more spongy. This is the boosted feel.

"Fade" means that the pedal is still firm, but the brakes are much less effective. In other words, you can push hard on the pedal, and the car doesn't slow as quickly as it normally does. Fade is not a problem with fluid or with the master cylinder, but is normally a heat problem with the pads.

If the pedal gets spongy when you use the brakes hard, or, in extreme cases, the pedal goes to the floor, the problem is normally the fluid boiling due to moisture (or really crappy fluid).

Wally Plumley
928 Specialists