There is a hissing sound around my brake master cylinder and I can't find exactly where it's coming from. But I notice that when I accelerate, the sound seems to go away and then come back when I let my foot off the gas. Does this seem like a vacuum leak? If so, how can I find it and fix it? Any help would be greatly appreciated.

 

Unless the car is idling up (fully warm) past 900rpms or so, then its not a vacuum leak. You can check the vacuum hoses around there and/or spray carb cleaner and if there is a leak it will make the car idle even higher.

 

The car doesn't seem to idle above 900rpm when warmed up. What else could could be the cause of this sound then?

 

car pulling a vacuum like its suppose to.

 

sounds like the brake booster has gone bad

 

bump for more help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adamrich33 &raquo;</TD></TR><TR><TD CLASS="quote">sounds like the brake booster has gone bad</TD></TR></TABLE>
x2

 

If the brake booster went bad, the brake pedal would be hard as hell. Like a rock almost.

 

the pedal is only hard when the car is off. When it is on, it softens and seems just fine.

 

Its not the brake booster gone bad. Your brakes wouldnt work very good and from what you said the pedal seems to be working right. Really sounds like a vacuum leak. I would try what is said already about the brake clean. Just spray it around by the sound until the idle changes and youve pinpointed the leak. Good luck

 

Thanks dc5_integra. I also think it is a vacuum leak.
But wouldn't a vacuum leak cause my idle to be unstable. For the most part, my idle is stable with an occasional(not very often) slight increase in rpm. Is this an indication of a vacuum leak? The hissing is very loud and can even be heard from within the car.

 

hondas/acuras with vacuum leaks always have a high idle. Does it only do it at idle or all the time even under load? Do you have an after market air filter like a K&N cold air intake? Because those tend to be kinda loud too.

 

The hissing is during idle but goes away when I accelerate. But once I let off the gas, it comes back. I know it is not my intake because I know the whistling sound it makes and I am hearing a hissing sound around the master cylinder area.

 

hmm did you try the break clean thing yet??

 

No, I will get to the brake clean thing soon. It's been so cold lately with the 2 blizzards and another snow fall CO been having these days.