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Thread: Intermittent brake shudder and ESP light

  1. #1
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    Intermittent brake shudder and ESP light

    I was driving my car the other afternoon ('03 RS6 in the US) and took it out for a back roads blast and then a couple mile hit on the highway...decided to air it out a bit up to a good clip since there was a clear open stretch of highway to 140 or so and immediately gave a light brake to slow back down. I noticed a pretty significant shudder in the front end that felt like a severely warped rotor. This kept up for about another mile off of the highway and then disappeared at lower speeds. Over the weekend (about a week later without driving the car), my son and I headed to the Audi USA cars & coffee in VA about 60 miles away...after 30-40 miles, we noticed a pretty strong shudder again when braking for toll booths (car was driven at normal highway speeds, nothing excessive). On the way home from the event, it got pretty severe and made me a bit worried that something could possibly be loose as it felt like it was right in the driver's front wheel...further down the road, still on the highway, it went away. One other funky note still on the same trip home is that when taking a sweeping highway overpass/onramp at 50-60, when coming back towards the straight, the ESP light started flashing and lost power right when I was getting ready to merge with light acceleration when coming out of the curve...this went off quickly though, but definitely affected the acceleration when the ESP was flashing.

    A few thoughts...I just installed new springs and struts that drop the car about 1.5". The car is running with a nubcake stage 2 tune (love it!) and a TCU tune.

    My first inclination is maybe a wheel speed sensor, any thoughts or input? Reason for the suspension replacement was a leaking DRC line that hit the driver's front wheel with a fair bit of oil and was worried a bit about oil on the brake pads, so maybe another suspect, but shouldn't cause the ESP light, just maybe a braking shudder.

    One final note, I took it for a short ride yesterday and ran it up to 100 or so...braked perfectly fine just as expected...no shudder at all.

    Any input is appreciated!

  2. #2
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    I would pull the wheel speed sensor and make sure it's clean. They already attract metal filings as it is, and with the hydraulic fluid in the general mix it would attract more if fluid got on it. I would think it might be misbehaving and causing the ABS to activate in error. It didn't do it on your drive yesterday, which largely rules out any mechanical issues. Oil on the brake pads is bad, but would just cause a lack of braking on that wheel.

  3. #3
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    Thanks for your input...I would agree and will pull the sensors, starting with the driver's side first since it seems to be more problematic. I may order a set of brake pads too just to get some fresh ones on there....

  4. #4
    Registered User hahnmgh63's Avatar
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    I pull them every time I do a brake job and clean them. Don't have to unhook the wiring, just the single Torx (I think it's Torx) screw and pull it out.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

  5. #5
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    Sounds like good advice...only driven the car about 3k miles since my ownership 9 months ago, so haven't had to do the brakes just yet!

    Fortunately my car has been garage kept and out of most weather for the better part of it's life...nice and clean underneath with 104k on it, so they shouldn't be seized like my 200k C5 A6 NY State car....

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