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Q: My brakes hiss back at me

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When i step on my brakes there stiff and hiss back at me they work still but not like they use to. I wanted to know if its my booster or my master cylinder, Ive also bleeded my brakes 2 times with no difference instead a bit stiffer than before. The first time they were VERY soft they almost didnt work. Now When it hisses it sounds like the dash but when you get out i cant determind if its the booster or master cylinder. Thank You.

My car has 258006 miles. I rebuilt my engine at 242,000 miles. My car has an automatic transmission.

That hiss you hear is a vacuum leak. That leads to the hard brake pedal. Power brakes rely on vacuum to make braking easier. The vacuum leak has reduced vacuum within the brake booster and is making the brake pedal hard - similar to older cars without power brakes basically. It may also be effecting your engine performance and economy. The leak can be the brake booster housing itself, or the vacuum connection to it. Have a certified technician look into the hard brake pedal as soon as possible.

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