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  1. #1
    Veteran Member Four Rings
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    Long brake pedal travel with large "dead zone"

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    Hey guys, I've been chasing this problem for a while and hoping for some insight.

    My S4's brake pedal travel is long with what feels like a large ~1.5-2 inch "dead zone" (no reaction from brakes). Also with engine off and pedal pumped until stiff, there is still has a pretty large amount of travel (probably the same 1.5-2 inches).
    This really doesn't inspire confidence in the car's braking... especially when I switch back to S4 from driving my Corvette, which has ZERO dead zone. At least the S4's brakes work well enough once the dead zone has been surpassed.

    When I push the pedal quickly through the dead zone (engine running), there is a noise from the pedal/booster, kinda like an air squishing noise if that makes sense. My wife thinks more of it than I do (my suspicion is it's only a symptom).

    Here's what I've done, in chronological order:
    • verified brake booster isn't leaking / losing vacuum, also replaced the firewall check valve
    • replaced brake fluid reservoir (Genuine part)
    • stainless steel brake lines all around (Centric parts). Bled brakes.
    • replaced all brake pads with EBC Reds. Lubed all slider pins. Bled front brakes.
    • rotors weren't that old when I bought the car, they're fine still
    • replaced master cylinder (TRW part)
    • bled 5L fluid using 2bar pressure (Motive bleeder) over 2 instances of bleeding (11 days apart). Also bled ABS using VCDS probably 10-15 times (through driver-front caliper bleeder). Have followed Bentley procedures, and then some, including tapping calipers with a rubber mallet. Also used pedal pump method with engine running and Motive bleeder also going @ 20psi. Seemed like I got all the air out. Reservoir never ran low on fluid after replacing MC.
    • Last night I played with the rod/nut between master cylinder and brake booster, but learned that only affects brake pedal position.


    Any additional ideas? Thanks for reading!
    Last edited by MetalMan; 06-11-2019 at 10:01 AM.
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  2. #2
    Veteran Member Four Rings
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    These are some of the next steps I am considering:
    • Rear calipers: I've read the dead zone issue can be caused by sticking/seized rear calipers; but: the pistons turned in fine when I changed pads, it's a CA car that doesn't have rust, and the parking brake seems to work great. Still I may dismount the rear calipers and see how they individually actuate from depressing the brake pedal.
    • Bleeding brakes with 2bar pressure, but pedal pump WITHOUT closing bleeders. Probably would have a slower return stroke on the pedal. Supposedly this helps with moving fluid through faster and may help get out any stubborn air bubbles.
    • Vacuum bleeding at the calipers? I have a vacuum bleeder hand pump.
    • Brake booster: it's one of the few things I haven't replaced/messed with; it's not a fun one to swap out unless you're already replacing the master cylinder. At least used ones are under $50 shipped.
    Last edited by MetalMan; 06-11-2019 at 10:43 PM.
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  3. #3
    Veteran Member Four Rings
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    Okay, tried extra-bleeding the rears today... put through 2L of fresh fluid, 1.3L right-rear and 0.7L left-rear. Used the Motive power bleeder @ 20+psi, left the bleeder open, and got in a real leg workout pumping the brake pedal (with slow pedal release on each stroke). At no point did I see ANY air exit the bleeder valves, and unfortunately (fortunately?) it made no difference on pedal feel.

    As noted in the first post above, the "air squishing" noise was a little more noticeable with increased pedal travel due to brake bleeding. I could more-so discern the noise during the "dead zone", almost like there's a buffer/damper that is actuated before the master cylinder is actually depressed. Perhaps this points a bit more to something going on with the brake booster?
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  4. #4
    Veteran Member Three Rings rguil's Avatar
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    b5 isnt well known for having the most responsive brakes. Its a "luxury" car after all LOL. The air squishy noise is normal, i think. Its happened on all the vag cars ive owned and worked on.
    Did you bleed the abs pump with VCDS?
    b5 s4. k24, 2.8 heads, rods, meth, corn, gutted, custom standalone, rear radiator, fuel safe, fully caged
    4.2 touareg. Locking diffs, air suspension.

  5. #5
    Veteran Member Four Rings
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    Quote Originally Posted by rguil View Post
    b5 isnt well known for having the most responsive brakes. Its a "luxury" car after all LOL. The air squishy noise is normal, i think. Its happened on all the vag cars ive owned and worked on.
    Did you bleed the abs pump with VCDS?
    I've had 3 B5s total, my prior [crashed] B5 A4 definitely didn't exhibit this long brake pedal travel situation.

    Quote Originally Posted by MetalMan View Post
    • .... Also bled ABS using VCDS probably 10-15 times (through driver-front caliper bleeder).
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  6. #6
    Veteran Member Four Rings christianb5s4's Avatar
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    Did you bleed your ABS enough times using VCDS? I kid. For what it's worth, on stock calipers I had that same thing but maybe not as severe. I was going to mention tired stock brake lines but you have SS already.

    You're welcome to feel my brakes albeit 18Zs up front to see if it feels similar?
    Imola 2001 Stage 3 S4: 316K - 156mph 1/2 mile - Completely Refreshed/Built BEL Motor - SRM K24s w/ Custom Turbosmart wastegates - Ringer Racing 4+ - Etspec - Cinesnow WG/Oil Lines - SRM V3 Intercoolers - AA built trans - 4:1 Diff - JHM Trio - 034 - H&R Coilovers - FCP - Bosch Motorsports - OZ Racing - SRM/SSAC exhaust - Tons of New OEM parts

    2009 C6.5 A6 3.0T Prestige - stock, daily driver

  7. #7
    Veteran Member Four Rings
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    Quote Originally Posted by christianb5s4 View Post
    Did you bleed your ABS enough times using VCDS? I kid. For what it's worth, on stock calipers I had that same thing but maybe not as severe. I was going to mention tired stock brake lines but you have SS already.

    You're welcome to feel my brakes albeit 18Zs up front to see if it feels similar?
    Seriously, I'm hoping I didn't shorten the ABS pump's life with all that bleeding!

    Perhaps we can do a "brake feel swap", you can see how bad mine is and I can see how good yours is? lol
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  8. #8
    Veteran Member Four Rings MacDaddy's Avatar
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    I think you may need to bench bleed your master again, its a bitch to get all the air out.

    Buy a master cylinder bleeding kit (it has various plastic adapters to go in the side and hoses that go into the small cap on the reservoir) and pump it till it stops blowing bubbles.

  9. #9
    Veteran Member Four Rings christianb5s4's Avatar
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    Quote Originally Posted by MetalMan View Post
    Seriously, I'm hoping I didn't shorten the ABS pump's life with all that bleeding!

    Perhaps we can do a "brake feel swap", you can see how bad mine is and I can see how good yours is? lol
    Anytime! Just let me know when you're free.
    Imola 2001 Stage 3 S4: 316K - 156mph 1/2 mile - Completely Refreshed/Built BEL Motor - SRM K24s w/ Custom Turbosmart wastegates - Ringer Racing 4+ - Etspec - Cinesnow WG/Oil Lines - SRM V3 Intercoolers - AA built trans - 4:1 Diff - JHM Trio - 034 - H&R Coilovers - FCP - Bosch Motorsports - OZ Racing - SRM/SSAC exhaust - Tons of New OEM parts

    2009 C6.5 A6 3.0T Prestige - stock, daily driver

  10. #10
    Veteran Member Four Rings
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    Quote Originally Posted by christianb5s4 View Post
    Anytime! Just let me know when you're free.


    Quote Originally Posted by MacDaddy View Post
    I think you may need to bench bleed your master again, its a bitch to get all the air out.

    Buy a master cylinder bleeding kit (it has various plastic adapters to go in the side and hoses that go into the small cap on the reservoir) and pump it till it stops blowing bubbles.
    Thanks for chiming in. Frankly I didn't bench bleed the MC because the Bentley manual says nothing about it.
    Came across a thread you made 2 years ago on a very similar topic:
    https://www.audizine.com/forum/showt...-non-ESP-b5-s4

    I bought a bench bleeder kit 6 years ago (also for an old B5 A4 that had squishy pedal after MC replacement...):
    https://www.amazon.com/gp/product/B00E6TXW6U/
    Never really used it, but would be awesome if I can use it for this.

    To be clear, are these the right steps to bench bleed in-car?
    1. Jack up the rear end so the MC is at least horizontal
    2. Unscrew brake lines from MC, and screw in plastic adapters to the brake line ports
    3. Hook up hoses to the plastic adapters, the other ends go into the fluid reservoir
    4. Slowly pump brake pedal, until no more air appears in the hoses
    5. Unscrew plastic adapters and reattach brake lines
    6. Bleed all 4 brakes, following Bentley procedure: RR, LR, RF, LF. Open LF bleeder and run ABS pump a few times
    Last edited by MetalMan; 06-12-2019 at 01:12 PM.
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  11. #11
    Registered Member One Ring
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    I tried all the above you did including SS brake lines with minimal improvement.
    The biggest difference came after checking the clearance between the end of the booster rod
    and the master cylinder. In my case, there was .065 clearance. I pulled out the bullnose pin
    and installed a .045 thick spacer, reassembled and pressure bled only at the ABS feed lines and
    now they feel and work like they should.

  12. #12
    Active Member Two Rings
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    It sounds like you have air in the system somewhere. I recently struggled with this and stumbled upon this thread which fixed my issue.
    https://www.audizine.com/forum/showt...ding+procedure

  13. #13
    Veteran Member Four Rings MacDaddy's Avatar
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    Quote Originally Posted by MetalMan View Post




    Thanks for chiming in. Frankly I didn't bench bleed the MC because the Bentley manual says nothing about it.
    Came across a thread you made 2 years ago on a very similar topic:
    https://www.audizine.com/forum/showt...-non-ESP-b5-s4

    I bought a bench bleeder kit 6 years ago (also for an old B5 A4 that had squishy pedal after MC replacement...):
    https://www.amazon.com/gp/product/B00E6TXW6U/
    Never really used it, but would be awesome if I can use it for this.

    To be clear, are these the right steps to bench bleed in-car?
    1. Jack up the rear end so the MC is at least horizontal
    2. Unscrew brake lines from MC, and screw in plastic adapters to the brake line ports
    3. Hook up hoses to the plastic adapters, the other ends go into the fluid reservoir
    4. Slowly pump brake pedal, until no more air appears in the hoses
    5. Unscrew plastic adapters and reattach brake lines
    6. Bleed all 4 brakes, following Bentley procedure: RR, LR, RF, LF. Open LF bleeder and run ABS pump a few times
    If you didnt bleed your master then i am 100% confident that is your issue, i was chasing a crappy brake pedal for years, you could bench bleed in the car, i dont see why it wouldnt work.

    When i bled mine in the vice i found i had to really vary how fast/slow etc to get all the air out. Simply pumping it willy nilly wasnt getting the air out, so id say have a helper to observe untill all the air bubbles are gone

  14. #14
    Veteran Member Four Rings
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    Quote Originally Posted by MacDaddy View Post
    If you didnt bleed your master then i am 100% confident that is your issue, i was chasing a crappy brake pedal for years, you could bench bleed in the car, i dont see why it wouldnt work.

    When i bled mine in the vice i found i had to really vary how fast/slow etc to get all the air out. Simply pumping it willy nilly wasnt getting the air out, so id say have a helper to observe untill all the air bubbles are gone
    I evaluated the potential for in-car bench bleeding last night. Looks like there's poor access to the rear-most brake line without removing the reservoir. And it turns out I don't have the correct MC adapter fittings.
    I checked out how level I could get the MC by jacking up the rear end. This was the highest I was willing to lift only the rear:
    https://photos.app.goo.gl/yAh9Dv7kqCKgib3h7
    https://photos.app.goo.gl/m81NLTuQjZ5boLfA8
    The MC was nowhere near level with that angle.

    Based on the information posted here (thanks guys!), this is what I tried yesterday:
    • Rear end raised up high
    • Pressure bleeder filled with fluid and pressurized to <5psi (just to make sure there was a steady supply of fluid into the res)
    • Ran ABS pump 25 times for right-rear. Witnessed no air bubbles. Bled ~600mL fluid.
    • Ran ABS pump 30 times on left-rear. Noticed not much fluid compared to right side, so loosened bleeder screw a little more. Ran ABS pump another ~25 times, and seemed to get a few bubbles out, certainly more fluid drained this time. Bled ~800mL fluid.
    • Decided to try cranking pressure bleeder up to 30psi as well [for "fun"], didn't really make a difference
    • Pedal still feels more or less the same, with the dead zone


    So one of my next steps will be to again jack up the rear end and try bench bleeding in-car. I'll buy this kit for the adapters (but use clear tubing):
    https://www.amazon.com/Dorman-13911-...dp/B001SG8ZC0/

    Quote Originally Posted by Maker View Post
    I tried all the above you did including SS brake lines with minimal improvement.
    The biggest difference came after checking the clearance between the end of the booster rod
    and the master cylinder. In my case, there was .065 clearance. I pulled out the bullnose pin
    and installed a .045 thick spacer, reassembled and pressure bled only at the ABS feed lines and
    now they feel and work like they should.
    I think this is very interesting... the "dead zone" doesn't feel squishy, it just kinda feels like there's no actuation of the master cylinder.
    Can you provide a little more description on this "bullnose pin"? How did you remove it from the booster (booster removed from car), and where did you put the .045 spacer?
    Last edited by MetalMan; 06-13-2019 at 03:30 PM.
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  15. #15
    Registered Member One Ring
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    Remove your master cylinder and you can pull out the bullnose
    contact pin from the end of the booster shaft with needle nose pliers.
    Take care not to drop it as you pull it out. It has small stem with a light press fit
    into the booster shaft.I used 2 small washers 1/4 dia. od .022 thick and placed them
    on the stem with a little bit of greese to hold them in place.You want to end up with .02 gap.
    Reinstall in the shaft end with needle nose pliers. Reasembled and bleed just the two feed lines at the ABS unit with the
    pressure bleeder. I finally have decent brakes.
    https://techtalk.mpbrakes.com/how-to...r-cylinder-gap

  16. #16
    Veteran Member Four Rings
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    Quote Originally Posted by Maker View Post
    Remove your master cylinder and you can pull out the bullnose
    contact pin from the end of the booster shaft with needle nose pliers.
    Take care not to drop it as you pull it out. It has small stem with a light press fit
    into the booster shaft.I used 2 small washers 1/4 dia. od .022 thick and placed them
    on the stem with a little bit of greese to hold them in place.You want to end up with .02 gap.
    Reinstall in the shaft end with needle nose pliers. Reasembled and bleed just the two feed lines at the ABS unit with the
    pressure bleeder. I finally have decent brakes.
    https://techtalk.mpbrakes.com/how-to...r-cylinder-gap
    I appreciate your additional explanation! Very interesting stuff, including that article. Definitely looks like it would be worthwhile to check out... perhaps I could pull out the master, take measurements and/or add spacers for the bullnose pin, bench bleed the MC on a vice, reinstall MC and bleed.

    Could also design & 3D print a tool similar to the Booster Pin Depth Gauge shown in that article instead of taking a bunch of measurements and doing math (reduce my chance for human error).

    As far as bleeding the 2 ABS feed lines, did you use any special tools/fittings or just slip a hose over the flared brake line and use a hose clamp?
    2001.5 S4 Avant: Motoza E85 Stage 1+, SSAC HFC DPs + Borla 3" catback, APR bipipe, AWE SMICs, DW300 fuel pump, TTV FW + B7 RS4 clutch, JHM shifter, metal clutch slave + SS line, 2.0T coils, lowered, Aero wipers, SS brake lines, receiving lots of love ($$$)

    2001 Corvette (C5) Z06: just getting started

    2001.5 A4 1.8TQM: gone and missed. Parting out.

  17. #17
    Veteran Member Four Rings MacDaddy's Avatar
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    That doorman kit is almost exactly what i used, looks like it comes with metric and standard adapters where mine was a “metric kit”.

    Pumping up the brake bleeder to 30psi shouldn't be nessisary if you have an ESP car, thas only required for non ESP cars like mine.



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