Brakes - malfunction behaves like ABS
12-12-2008, 01:11 PM
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Brakes - malfunction behaves like ABS
1996 A6Q Avant - 156,000 miles
When applying the brakes, I am getting some pedal fade and then some "feedback" from the pedal that behaves like the thumping you get from ABS. It's intermittent, but more frequent now, especially in stop and go traffic. Car always stops, but you keep that funny feeling in your stomach each time you hit the brakes...
CEL came on and code reader said brake light switch. I've replaced it once several years ago, and did so again, but it didn't change the brakes' behavior. Just made the light go off.
One more little nugget: for several years (this is our "backup" car), there's been a horrendous whining at cold startup for 60 - 90 seconds. Sounds like a jet preparing for takeoff! Mechanic has been telling me it's the ABS pump, but we've let it go because we look at ABS as "secondary" to actual brake function. Perhaps that was a bad idea, but I wanted to throw it out there.
Any thoughts? We are trying to rule out master cylinder, slave cylinder and control unit. Indy mechanic is stumped at the moment. I'd love to get enthusiast feedback!
Thanks!
When applying the brakes, I am getting some pedal fade and then some "feedback" from the pedal that behaves like the thumping you get from ABS. It's intermittent, but more frequent now, especially in stop and go traffic. Car always stops, but you keep that funny feeling in your stomach each time you hit the brakes...
CEL came on and code reader said brake light switch. I've replaced it once several years ago, and did so again, but it didn't change the brakes' behavior. Just made the light go off.
One more little nugget: for several years (this is our "backup" car), there's been a horrendous whining at cold startup for 60 - 90 seconds. Sounds like a jet preparing for takeoff! Mechanic has been telling me it's the ABS pump, but we've let it go because we look at ABS as "secondary" to actual brake function. Perhaps that was a bad idea, but I wanted to throw it out there.
Any thoughts? We are trying to rule out master cylinder, slave cylinder and control unit. Indy mechanic is stumped at the moment. I'd love to get enthusiast feedback!
Thanks!
12-12-2008, 10:23 PM
#3
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If you have the secondary air pump system on your AFC engine, that is probably the whining.....
you're hearing on cold start-up. You'll know if you have this system if there is a plastic hose that runs across the right front (passenger side) of the engine from the airbox.
12-29-2008, 08:08 PM
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Re: If you have the secondary air pump system on your AFC engine, that is probably the whining.....
Yep, looks like that's what's causing the squealing. Confirmed by mechanic today. I'm guessing I have to replace the doggone thing. Is this a common failure for the C4? Thanks so much for your help!
12-29-2008, 08:11 PM
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Car usually sits outside, just begging to be driven. No work recently.
But something I will definitely check. It's had us stumped for several weeks. Thanks for your help!
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