Is my Brake Booster bad?

[tundrayetti]

Hey guys, I've got about 500 miles on my rebuilt 22RE and for the last 100 miles or so, when my foot is on the brake, my engine idles down every other second. Take my foot off the brake, and idle levels out immediately. I don't have any experience with the brake booster. Is it bad?

 

[SV_Dude]

It sounds like the diaphragm inside the booster is bad. Do a search and you'll find lots of info on how to test it.

 

[fourwd1]

I wouldn't jump to the booster being bad.
First, how are the brakes? Do they seem harder and need more pedal effort?
How does the engine idle? Is it smooth?
What is your idle speed set to?

 

[tundrayetti]

It sounds like the diaphragm inside the booster is bad. Do a search and you'll find lots of info on how to test it.

Thanks. I'll do a search and see what I come up with.

 

[tundrayetti]

I wouldn't jump to the booster being bad.
First, how are the brakes? Do they seem harder and need more pedal effort?
How does the engine idle? Is it smooth?
What is your idle speed set to?

Pedal seems normal. No difference in effort.

Engine idles smooth as can be (just rebuilt).

Not sure how to determine my idle speed without a tach. I will say, that it seems to be set a great spot according to what it sounds like.

 

[SV_Dude]

I wouldn't jump to the booster being bad.

I never said to jump to that conclusion. I just advised him to test it because a change in engine idle/rpm is a common symptom of a bad booster... along with other signs but that's why I told him to search.

Tundra: If your booster is on the cliff of going bad you may not notice a change in the brakes right away until the diaphragm inside of the booster is torn or worn more.

 

[ToyoTech]

usually if the booster is bad. your idle goes up since its a vacuum leak. you can always disable the booster by clamping off the hose to the booster and try it again at idle and stopped. i wonder drive it like that and if you do. find an open area

 

[fourwd1]

Pedal seems normal. No difference in effort.

Engine idles smooth as can be (just rebuilt).

Not sure how to determine my idle speed without a tach. I will say, that it seems to be set a great spot according to what it sounds like.

Then it's not likely the booster, if it were bad you'd notice it in the pedal, and the vacuum leak would typically create a rough idle.

The reason I wanted to know the idle rpm is because if your idle is set too high, you will get an idle fluctuation when your foot is on the pedal, and it will go away once your foot is off.