Rubbing noise from rear of 520i

[GarethHart]

I've got an annoying rubbing or grinding noise coming from what sounds like the rear of the car. It's a N reg 520i; 135,000 miles.

The noise (bit like a low pitched woo - woo - woo noise!) is there constantly at slower speeds until I brake - then it goes. Also seems to dissappear at higher speeds.

I washed the car the other day with a jet wash and the noise vanished for a while but came back after 20-30 mins driving!

Anyone any ideas?

Thanks

GH

[Ross]

Inspect your brakes

[GarethHart]

I had the brakes looked at and they said they were fine? Maybe I should get a second opinion?

[SnakeyesTx]

Well, since you had the brakes checked out, they obviously checked the rim to make sure it wasn't being ridden on by the dust plate.

I'm going to have to go with drive-shaft center support bearing starting to fail, the noise you experience is a common symptom. This is the "starting small" theory.

Worst case scenarios would be differential carrier bearing, or rear axle bearings starting to fail. When you apply the brakes while coasting to a stop, you're putting load against the driveline which would "take out the slack" so to speak muffling the noise.

When you powerwashed the car, I can only imagine that maybe something cooled down and tightened up a little bit to mute the noise but came back after 20-30 minutes of driving and rotational friction warming something back up to cause the slack and noise.