A8 Brake judder Help!!!
Discussion
I am having a nightmare. My A8 which runs beautifully has developed judder under braking at speed. I have checked the discs and they are all fine. Looked at the multi link and all bushes seem fine. I am tearing my hair out trying to figure out the cause. So please throw any ideas my way. Could it be the ABS cutting in uneccessariy?? If so can it be reset? Can you run a diagnostic which will tell me the cause???
This may not be the same problem, but if it helps, great!
On My S4 Avant 2.7 Bi-turbo, the brakes gave a similar symptom - the judder was more felt, through the brake pedal, by the driver than anything else.
Checking the signal from the ABS wheel speed sensor on each hub revealled that one sensor was giving spurious reading. Connecting an oscilloscope to the wires gave a reading of roughly the correct specification on the other three sensors, but on my rear right wheel the reading was off the screen in scale. In theory this wrong signal made the ABS cut in when no "locking-up" was actually happening.
In my case, a new ABS speed sensor was added - bu this involved getting the old one out. As the car was 6 years old, the sensor had become corroded in the hub, and snapped in two when we tried to fork it out. This meant getting the whole hub assembly off the car, and poking the broken sensor out from the other side.
This unfortunately means taking the lower arm off the hub ass'y, which is held in place by a captive nut (rivet type as opposed to a nut and bolt). You need a new captive nut and also a captive nut gun to re-assemble.
In parts I spent around £400, but in labour it would cost you maybe 5 - 8 hours.
I work at an Harper and Hebson Audi in Carlisle, so got a good deal on getting it fixed, but the labour could be a killer bill.
On My S4 Avant 2.7 Bi-turbo, the brakes gave a similar symptom - the judder was more felt, through the brake pedal, by the driver than anything else.
Checking the signal from the ABS wheel speed sensor on each hub revealled that one sensor was giving spurious reading. Connecting an oscilloscope to the wires gave a reading of roughly the correct specification on the other three sensors, but on my rear right wheel the reading was off the screen in scale. In theory this wrong signal made the ABS cut in when no "locking-up" was actually happening.
In my case, a new ABS speed sensor was added - bu this involved getting the old one out. As the car was 6 years old, the sensor had become corroded in the hub, and snapped in two when we tried to fork it out. This meant getting the whole hub assembly off the car, and poking the broken sensor out from the other side.
This unfortunately means taking the lower arm off the hub ass'y, which is held in place by a captive nut (rivet type as opposed to a nut and bolt). You need a new captive nut and also a captive nut gun to re-assemble.
In parts I spent around £400, but in labour it would cost you maybe 5 - 8 hours.
I work at an Harper and Hebson Audi in Carlisle, so got a good deal on getting it fixed, but the labour could be a killer bill.
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