My e38 has started making a mild knocking noise, mainly when I'm backing up, and when the car is cold. Sounds to me like it may be coming from the right side, but hard to tell. Wheel bearing going bad maybe? Noise vanishes after warmup.
Is it worse when you turn the steering wheel?
Next time you change the oil put it up on blocks and see if you can make it happen by turning the wheel by hand.
--scott
Thinking low power steering fluid? Nah, I don't think so, in fact, I know it's not that. Turning the wheel doesn't make any difference. I think this sound may be related to a similar, but slightly different sound I get on cold mornings when I'm driving down the road before the car warms up.
Any of the multitude of rubber bushes or ball joints going bad? ..or is it just the brakes grabbing first thing?
If it's actually a bearing, it will usually be worse if the wheel is turned to the side, as it will put more lateral force on the bearing.
Also, it could be something loose scraping against the tire slightly, but that again would change depending on the position of the wheel.
Could even be control arm bushings. But you'll know if you put it up and turn the wheel by hand.
--scott
I've the same problem on my 01 e39. It's there when you only pull off and dissappears after 50 yards.
Does yours only happen then the car is moving in gear? If you depress the clutch is it still there? My thinking was perhaps the cluth bearing, car is in next week so will know more then.
I've changed my front upper/lower arms but hadn't thought about a sticking caliper - could be.
let us know how you get on.
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