[kgbronco]

I have a 41 chevy coupe street rod. When I apply the brakes my idle goes up about 2-3 hundred rpm. I have a bendix booster on it I bought from a speed shop and is mounted to the frame under the drivers floor. The car has been just sitting in the body shop for about 1 1/2 years. I built the rest of the car about 5 years prior to that. I have not done alot of work on this problem yet but my fear is that the booster has a hole in the diaphram, does this seem logical or could it be something else. I have noticed since I got the car out of the body the brake pedal does not come all the up after removing your foot. I'm not sure if these two problems are linked or not.

[sunsetdart]

You didnt say if they are power brakes. If they are, then you may have a crack in the vacuum hose that goes to the manifold, so when you apply the brakes, the crack allows vacuum out of manifold. Thats why the RPM's go up.

[ScoTFrenzel]

The possibility exists that the diaphram in your booster has a crack in it, and the pedal movement opens that crack allowing a vacuum leak.

If you want to check for a leak and don't want to use the usual WD40 or carb cleaner spray method into your booster, use starting fluid....
very gently, don't over do it.... it doesn't leave any residue.

[kgbronco]

Yes, I do have power brakes. I have checked all the lines and they seem to be in good shape. Does'nt this pretty much leave the booster as the problem.

[302 Z28]

Originally Posted by sunsetdart

You didnt say if they are power brakes. If they are, then you may have a crack in the vacuum hose that goes to the manifold, so when you apply the brakes, the crack allows vacuum out of manifold. Thats why the RPM's go up.

The title of the post indicates he has power brakes.

Vince