Brake Pedal Firm on Start (Pedal does not depress)

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02-13-2010 | 11:55 AM

#11

porsche911targa

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Joined: Sep 2008

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From: Massachusetts, USA

My Ride: 2006 525XI, Jet black on Dakota beige. Premium and winter packages. I consider myself a purist and intend to keep my car absolutely stock and shiny. 2008 328I Convertible, Sapphire black on beige interior. Premium package, NAV, iPod adapter. Retired: 2002 325I, Titanium silver on black leather. Premium package. Absolutely stock and proud of it.

Maybe it needs bleeding.

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02-13-2010 | 12:01 PM

#12

turboawd

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Joined: Jul 2008

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My Ride: 2006 BMW 550i

Quote:

Originally Posted by porsche911targa

Maybe it needs bleeding.

this problem has nothing to do with the hyrdaulics of the brake system.

the brake booster vacuum is bleeding off when the car is off. this is either due to a bad booster or bad check valve.
normally most cars hold vaccum in the booster, and the brakes work even if the engine is off. pump the brakes a few times when the engine is off, and the pedal gets hard. why? because there is no more vacuum assist, until you start the engine again.

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02-13-2010 | 03:09 PM

#13

fryeje

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Joined: Dec 2008

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My Ride: 2005 545i Sport 6sp,

Quote:

Originally Posted by turboawd

+1 In fact, if the brakes needed bleeding that would mean there is air in the system and that makes them softer not harder. My '05 545i (MT) has always had a hard brake pedal before starting. 95% sure it's a leaking check valve but have not repaired because it not high priority yet.

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