Strange problem with breaks.
Discussion
Hello All,
Any views, opinions on the following gratefully received.
Strange problem with the wives car - 2001 Audi 1.8 A4 estate (older shape) 85,000 miles.
Strange noise coming from the brakes, a kind of thud / drone that lasts for about 1-2 seconds and appears to be emanating from the ABS pump. You also feel a slight change in resistance from the pedal. This typically happens under light breaking when the car has nearly stopped, maybe 5mph.
I'm guessing the ABS pump has died. If you disconnect the pump and run the system as non ABS it behaves normally. I'll probably replace the pump but am concerned that maybe a duff wheel sensor could also cause this?
Any ideas?
Cheers,
Matt
Any views, opinions on the following gratefully received.
Strange problem with the wives car - 2001 Audi 1.8 A4 estate (older shape) 85,000 miles.
Strange noise coming from the brakes, a kind of thud / drone that lasts for about 1-2 seconds and appears to be emanating from the ABS pump. You also feel a slight change in resistance from the pedal. This typically happens under light breaking when the car has nearly stopped, maybe 5mph.
I'm guessing the ABS pump has died. If you disconnect the pump and run the system as non ABS it behaves normally. I'll probably replace the pump but am concerned that maybe a duff wheel sensor could also cause this?
Any ideas?
Cheers,
Matt
This is nearly always either a duff sensor, or a cracked/broken reluctor ring. Either of these can reduce the signal received by the ECU enough at very low speeds to make it appear as though the wheel has locked.
Matt K1064 said:
Strange problem with the wives car
How many do you have? Mr2Mike said:
This is nearly always either a duff sensor, or a cracked/broken reluctor ring. Either of these can reduce the signal received by the ECU enough at very low speeds to make it appear as though the wheel has locked.
That's great, thank you. Any easy ways of tracing which wheel is causing issues? Can you just disconnect the sensors one by one and see which one stops ths problem?Matt K1064 said:
Strange problem with the wives car
How many do you have? Just the one wife but it seems like i'm running about ten sometimes!
No you can't disconnect sensors; this will just flag a fault as soon as you start driving and the ABS will be deactivated.
A cracked reluctor ring will be pretty obvious by inspection, but a duff sensor is harder to find. Ideally you would use an oscilloscope to look at the voltage levels, but a multimeter will give some kind of indication. Without knowledge on what the actual voltage should be for any given speed (voltage increases with speed with VR sensors) you can only compare outputs between sensors.
A cracked reluctor ring will be pretty obvious by inspection, but a duff sensor is harder to find. Ideally you would use an oscilloscope to look at the voltage levels, but a multimeter will give some kind of indication. Without knowledge on what the actual voltage should be for any given speed (voltage increases with speed with VR sensors) you can only compare outputs between sensors.
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