Expert: Sean Halliday - 7/20/2007

Question
I have been hearing a horn or vacuum noise while driving. It happens when I am trying to maintain a certain speed between 15-40 mph. It goes away when I accelerate or let off of the gas. If it happens at higher speeds I could not tell you. I have checked for obvious vacuum leaks with brake cleaner and have found nothing. Have you ever heard of such a thing? My car seems to be running just fine. Does it sound like a power brake booster problem, if so, how do I check?

Answer
If your brake booster had a leak,your brakes would be very hard to push.Without actually hearing this noise i would be guessing,sorry but there are a multitude of reasons for this,,,,i.e. drive shafts.....pulleys...belts...transmission bearings..engine bearings...ABS....vacuum....water pump ...a/c,,,etc,,,etc,,,,,if the car runs ok then dont fix it,,,,live with it or have a pro take a look.Did you look at the brakes?.pads?