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  1. #1
    Veteran Member Four Rings xdewaynex's Avatar
    Join Date
    May 24 2009
    AZ Member #
    42854
    My Garage
    98.5 A4 1.8TQM
    Location
    Danville, KY

    Pre Facelift to Facelift Booster swap help

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    I swapped to a facelift brake booster on my pre facelift A4 last year, noticed it placed the pedal position further towards the seat. Last few times Ive driven it, the rear brakes have locked up but will release after sitting for about 15min. I done the swap because I done an abs delete along with 6 piston fronts and 4 piston rears. Was curious if someone has done the booster swap and done something different to get the pedal position back to stock. With the car running or off, I have maybe 1/2" of pedal travel.
    1998.5 A4 1.8TQM My Build

  2. #2
    Veteran Member Four Rings walky_talky20's Avatar
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    Jun 30 2008
    AZ Member #
    30427
    Location
    Erie, Pennsylvania

    Your rear brake issue is most likely because the master cylinder is not being allowed to release fully. The pedal and master cylinder rod are being held slightly pushed, and is not fully achieving the "dump" position. So it is holding pressure in the lines.

    Maybe you need the pedal or pedal cluster from a facelift car, too? I have never swapped between them, so I don't know exactly what is different there.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear
    2006 Passion Red Volvo V50 T5 AWD 6MT
    2000 Satin Silver Passat 1.8T FWD Wagon, Slippy Tiptronic, 15" Hubcaps
    2001 Aluminum Silver Metallic A4 Avant 1.8TQM (winter sled)

  3. #3
    Veteran Member Four Rings xdewaynex's Avatar
    Join Date
    May 24 2009
    AZ Member #
    42854
    My Garage
    98.5 A4 1.8TQM
    Location
    Danville, KY

    Quote Originally Posted by walky_talky20 View Post
    Your rear brake issue is most likely because the master cylinder is not being allowed to release fully. The pedal and master cylinder rod are being held slightly pushed, and is not fully achieving the "dump" position. So it is holding pressure in the lines.

    Maybe you need the pedal or pedal cluster from a facelift car, too? I have never swapped between them, so I don't know exactly what is different there.
    The more I thought about it, definitely has to be a problem with the master cylinder. I do remember the pedal adapter that bolts to the booster rod was slightly different but swapped over the pre facelift one and tossed the other. I feel like this may be the reason why the brake pedal sits further out past the clutch and accelerator pedals.
    1998.5 A4 1.8TQM My Build

  4. #4
    Veteran Member Four Rings walky_talky20's Avatar
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    Jun 30 2008
    AZ Member #
    30427
    Location
    Erie, Pennsylvania

    Yes, I believe it is all related.

    The technical name for the critical adjustment here is "Brake Pedal Free Play" adjustment. Without enough free play at the top of the pedal travel (usually there is a specified minimum amount noted in the repair manual), bad things can happen. Such as the brakes remaining stuck on when the pedal is fully released.
    ^Don't listen to this guy, he's not even a mechanic.
    2001 Laser Red A4 1.8TQM, 5-Speed Swapped, 4.11 Final Drive, APR 93, 2.5" Exhaust, ST Coilovers, 034 RSB, A8 Brakes Front & Rear
    2006 Passion Red Volvo V50 T5 AWD 6MT
    2000 Satin Silver Passat 1.8T FWD Wagon, Slippy Tiptronic, 15" Hubcaps
    2001 Aluminum Silver Metallic A4 Avant 1.8TQM (winter sled)

  5. #5
    Veteran Member Four Rings xdewaynex's Avatar
    Join Date
    May 24 2009
    AZ Member #
    42854
    My Garage
    98.5 A4 1.8TQM
    Location
    Danville, KY

    Quote Originally Posted by walky_talky20 View Post
    Yes, I believe it is all related.

    The technical name for the critical adjustment here is "Brake Pedal Free Play" adjustment. Without enough free play at the top of the pedal travel (usually there is a specified minimum amount noted in the repair manual), bad things can happen. Such as the brakes remaining stuck on when the pedal is fully released.
    Am I right in thinking that while I was trying to get the pedal threaded onto the rod coming out of the backside of the booster, I may have messed with adjust that pushes into the master cylinder? If so, is there proper adjustment I need to abide by?
    1998.5 A4 1.8TQM My Build

  6. #6
    Veteran Member Four Rings xdewaynex's Avatar
    Join Date
    May 24 2009
    AZ Member #
    42854
    My Garage
    98.5 A4 1.8TQM
    Location
    Danville, KY

    After going back out to the garage and looking at the booster, the rod doesnt adjust but after I got everything bolted back up to the firewall, I did notice the adjuster on the brake pedal seems to be quite a bit too long which seems to be the reason why the pedal sticks so much further out from the clutch and accelerator pedals. Ive been fitting with the clip to get the brake pedal off so I can try and shorten the adjuster on the brake pedal.
    1998.5 A4 1.8TQM My Build

  7. #7
    Veteran Member Four Rings xdewaynex's Avatar
    Join Date
    May 24 2009
    AZ Member #
    42854
    My Garage
    98.5 A4 1.8TQM
    Location
    Danville, KY

    Been looking at pictures online of both boosters and it seems like the portion of the facelift booster that protrudes through the interior of the car is longer than the pre facelift.
    1998.5 A4 1.8TQM My Build

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