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Yesterday I started my vehicle, applied brakes before putting in reverse, and noticed a continous hissing sound every time I apply the brakes. The brakes are not working properly. It takes pumping several times and is very hard to stop! The hissing sound is continous as long as the brakes are applied. This is an all of a sudden problem ! Havent heard this before until yesterday! Brakes working ok prior to yesterday. Noticed brakes have gradually required a little more stopping time but no hissing sound!.SUGGESTIONS? Thanks in advance........ Sincerely. Bobby Graham . ..

My car has 123000 miles.
My car has an automatic transmission.

Hi there. It sounds like the brake booster could be failing. Many times a leaking master cylinder is the cause. The master cylinder can leak brake fluid into the booster over time without anyone really noticing. The brake fluid is corrosive and weakens the vacuum chambers in the booster which eventually fail and produce the hissing sound you’re hearing. I suggest having a technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a hissing noise when pressing the brake pedal inspection.

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