Pierburg Pump, Brakes, etc., etc.

[John Lagnese]

I've only had one stick at a time. The brake pedal gets hard and a bit higher. One lister suggested it was the brake hose. I got one and will change it tomorrow.
John
  ----- Original Message ----- 
  From: Alex Kowalski 
  To: John Lagnese ; quattro at audifans.com 
  Sent: Saturday, May 06, 2006 9:41 PM
  Subject: Re: Pierburg Pump, Brakes, etc., etc.


  This is syndrome that occurs when the the brakes drag when the underhood temperatures get hot.  Not just normally warm, I'm talking about sitting at idle for 10-15 minutes or running the car hard on a very warm day.  The brakes start out perfectly normal, then gradually they keep coming on all by themselves, sapping power and changing the feel at the pedal noticeably, until you have either stopped driving because you're worried or stopped driving because you've ruined them completely.  

  There are a few references to this phenomenon in the Audifans archives, and my car is suffering from it:

  http://www.audifans.com/archives/1997/05/msg01603.html

  Some people have claimed that it is the brake booster (the "servo" in my post) but on my car it doesn't appear to be so.  I think it's the "bad master cylinder under heat" problem mentioned here: 

  http://www.audifans.com/archives/1995/11/msg00420.html
  http://www.audifans.com/archives/1999/06/msg00447.html
  http://www.audifans.com/archives/1999/06/msg00460.html

  There are a few others dealing with diagnosing the problem definitvely:

  http://www.audifans.com/archives/1999/06/msg02997.html

  If you look a little harder you'll find the diagnosis procedure once the brakes have "stuck", which is basically to loosen the brake lines at the master cylinder and see if any fluid shoots out of there.  On my car it did.  Then I tried cooling the master cylinder down with ice packs to see if I could also get the brakes to free themselves up.  That worked, too.  So I'm thinking of replacing the master cylinder. 

  It seems to be strictly temperature-related, but I'm also wondering whether it's deposit-related, and could possibly be cured by removing and cleaning the reservoir and master cylinder thoroughly.  I haven't seen any discussions about that recently, so I posted the question to find out if anyone had done it.  

  In any case, even if nobody likes that idea, the master cylinder isn't very expensive.  It's a lot cheaper than the hydraulic servo that drives it.

  Cheers,
  Alex






   
  On 5/6/06, John Lagnese <jlagnese at massed.net> wrote: 
    Why, what is the problem again? I also have a intermittant brake sticking
    problem.
    John
    ----- Original Message ----- 
    From: "Alex Kowalski" <hypereutectic1 at gmail.com>
    To: <quattro at audifans.com>
    Sent: Saturday, May 06, 2006 7:56 PM 
    Subject: Re: Pierburg Pump, Brakes, etc., etc.