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Old 11-22-2003, 06:22 PM
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79450sl 79450sl is offline
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Join Date: Jan 2003
Location: Chicago
Posts: 36
Well guys, I bled the brakes again and it is still the same. I then pulled the master cylinder out, tore it down, cleaned it (the seals looked like they were brand new) and put it back together. Still no improvment.

While test driving the car I could hear what sounds exactly like a vacuum leak (could not hear it before due having the top down.......its getting cold in Chicago, so the hard top is on it now). I stuck my head down by the pedals, and as the brake pedal is depressed I could hear the "hissing" associated with a vacuum leak. The sound would continue until the pedal was returned to a resting position. If I were to hold down the pedal and slightly separate the rubber boot surrounding the "brake unit pressure rod" (as the shop manual refers ro it) the hissing became louder. I removed one end of the boot from the booster side (closest to the firewall) and depressed the pedal and the "hiss" was much more noticable.

Another thing I noticed is that when the brake pedal is depressed, the RPMs begin to rise. The farther I push the pedal down, the higher the RPMs get. Its only a difference of idle to idle+300 RPM, but definatly noticable.

My questions here are

1. Should the RPMs change that much when in park, at idle when the brakes are applied??

2. Should there be a consistent "hissing" while the brake pedal is depressed??

3. Is the consistent "hissing" a vacuum leak causing flutuation in engine RPM????

This is driving me insane!!!!!! I have to get the car in for emmisions testing by Dec. or they suspend my liscense.


Thanks guys.....
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