I just brought my car to the dealer for them to check the noise of my car. It makes pssss sound like an air compressor makes noise when its full of air. they took it for a test drive, and come back with this answer " It is a brake booster noise and there is no solution right now. All the IS will make this noise". I told that but it didnt make any noise like this before and he just looked at me and and said nothing. Any of you has this problem? my car has 9k miles on it, and i just had the 10k service done.

 

All cars with vacuum assisted brakes make that noise. it's normal

 

Actually it is not normal.

An air leaking sound coming from the brake booster typically indicates a damaged booster. You would feel a stiffer pedal though if it was actually leaking badly.

Perhaps it is a known issue to the IS models, first I have heard of it, but other members might be able to chime in about it with their own cars.

 

Now that you mention it, I have about 6500 miles and can notice the sound when my windows are rolled down. Not sure what it was, but don't have any problems of being stiff. Only problems with the F-sport brakes is the squeak it makes, which seems to be normal looking at other threads...

I'm with you, I'm also interested if anyone knows what this PSSS sound is when braking.

 

Perhaps it's the AC compressor kicking in? can post a video?

 

no its not an AC thing. Its the brake. the service tech told me that and he said it happens with all the IS. there is nothing they can do right at this moment
Its not a loud sound that you can notice easily, so even if i take the video, you won't hear it. also, i have an f sport intake and f sport exhaust, the noise from those things will cover up the psss sound. But i bet you have heard of the pssss sound when the air compressor is full of air.

 

It is not that bad or serious that the pedal is stiff. its just you hear it and you know it there but just don't know what is it or how to ignore it because i care about my car and being OCD about it.