Bimmerfest - BMW Forums - View Single Post - sound of pressure being released...
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Old 01-23-2013, 08:01 AM
floydarogers's Avatar
floydarogers floydarogers is offline
Pedant and Curmudgeon
Location: Renton, WA
Join Date: Oct 2010
Posts: 5,455
Mein Auto: 335d, 328d, Toyota T100
Might be a leaking check valve on the brake vacuum booster. If you shut down the car and wait until the hiss goes away, do you still have brake assist?
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