Hissing sound near master cylinder - Honda Prelude Forum

FamilyPrelude · 01-22-2010, 08:21 PM

I need some help please.
I have a 1994 vtec, I keep hearing a hissing sound under the hood near the brake master cylinder while the car is running and then when you shut the engine off, it still hisses for about 5 - 10 seconds
I can't for the life of me find it. Seems like a vacuum hose?

Can anyone tell me if you have had this before, or how I might find a vacuum hose that is bad or leaking?
I don't have any CE lights, car runs perfect, just a new sound I can't figure out

I would appreciate any help.
I have searched forum, found one other person, but nothing on what it was.

Thanks.

kimara3002 · 01-23-2010, 04:34 AM

get a spray bottle and fill with dish soap and water and spray your bay down .. make sure you hit all the areas where the vacuum hoses are etc.. if you see bubbles then bingo

FamilyPrelude · 01-29-2010, 01:57 PM

With the help of a friend, the hissing noise was the brake booster.
Hope this might help someone in the future.

~Ry · 01-29-2010, 02:56 PM

i was about to say, if it is air and its right by the master cylinder....brake booster

Crazi3ge3 · 01-30-2010, 01:48 AM

My car is like that also. is it bad? because my brakes work fine. no lost pressure or anything

FamilyPrelude · 01-30-2010, 09:57 AM

What is happening, is there is a small whole that let's the pressure relieve once the car is shut off, but the booster will let the brakes work.
The tear in the diaphragm will get worse, so it will need to be replaced.