Brake booster ?

[7tee]

While stopped and at idle I noticed as I pushed on the brake and held it firmly, my rpm kept slowing down to the point I thought it was going to die until I released the brake and it came back. This is a manual tranny, stock motor with a very small cam. Initial timing is 12*, idle rpm 720 and vacuum is 14" with drum brakes all around. Was wondering if the booster was on the way out. There are no sounds coming from it like an air leak, just wondering...Ed

[7tee]

ttt

[Custom/Ten]

I think your on the right track. To test you booster hook it up to a vacuum pump and crank it up to 20 inches. If it won't go up it's bad. If it will go up then pump it to 20 and let it sit for a few minutes. If it won't stay at 20 it's bad. If you don't have a vacuum pump you can get one for about 20 bucks at a parts store. I'll post a pic so you can see the tool in case you don't know what the tool looks like.

[Custom/Ten]

[7tee]

Originally Posted by Custom/Ten

I think your on the right track. To test you booster hook it up to a vacuum pump and crank it up to 20 inches. If it won't go up it's bad. If it will go up then pump it to 20 and let it sit for a few minutes. If it won't stay at 20 it's bad. If you don't have a vacuum pump you can get one for about 20 bucks at a parts store. I'll post a pic so you can see the tool in case you don't know what the tool looks like.

Thanks Custom I may need to check into a gauge. However I did pull a vacuum from the hose at the booster and I had 15".

[Custom/Ten]

14 and 15 are a little low. Unless you have a big cam I would expect to see 18 to 20.

[7tee]

Originally Posted by Custom/Ten

14 and 15 are a little low. Unless you have a big cam I would expect to see 18 to 20.

That's what I've heard (being low) I may also need to do a compression test to see what's going on there also...

[7tee]

Vacuum leaks yeah I've sprayed everything with no luck...Thanks Ed