D2 A8/S8 (1997 - 2003)
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a Hard brake pedal (like when the car is off)
Posted by: 02D2 (101810) on 2017-09-28 20:13:57
In Reply to: About to dig into my brakes again... and suspension? posted by hyperlogos on 2017-09-27 21:53:07

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is usually the result of a bad brake booster. The booster is supposed to "boost" the brake pedal force on the master cylinder. that boosted force is assisted by engine vacuum. when the engine is off the booster has no vacuum and the brake pedal is hard to press because it is not assisted by the brake booster.....consequently if the pedal is hard while the engine is running you have a bad brake booster or a really bad vacuum leak going to the booster (which I think you would be able to hear if it was pulling air that bad or the engine would be idling really high or rough.
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All messages | Search Forums | Return to D2 A8/S8 (1997 - 2003)