I have an odd noise that I am slightly concerned about. I am going to book the car in to see the dealer, but thought some of you might know what this could be.

First, the history ...

Car is an 07 Octavia II vRS TDi PD. 38,000 miles, just approaching its 3rd birthday in July, so still in warranty. 18" wheels, but no performance mods at all. Has had the ABS unit replaced under warranty and also the compressor for the aircon. Other than that, nothing wrong with it. Mostly plods up and down motorways, with the occasionalcountryside blast when I get chance. Never been on the track, never been involved in an accident. Manual., not DSG.

Now, the problem...

Over the last week a grinding/rattling sound has developed from under the car. It's hard to know exactly where it's coming from, and it's hard to know exactly when it started because having the radio/iPod on masks the sound. If you turn the stereo off you cna hear what sounds like a piece of metal being dragged along under the car, periodically bouncing. This might be a strange thing to say, but it sounds like a rotational noise. I have been under the car and nothing is haning off or loose - in fact I'm quite impressed by how sound it all looks under there.

The sound is noticeably worse when you have the windows down (obviously) and reflects back loudly off passing cars/buildings.

I have tried the following tests to rule stuff out...

1) Sitting stationary and revving the engine with the clutch depressed and released. No sound. Not engine related.

2) Allowing the car to coast down a hill in neutral with the clutch all the way out. Noise continues, leading me to think it isn't gearbox or clutch related.

3) Noise doesn't seem to be appreciably louder or more frequent at higher speeds, nor under load. Car displays no warning lights, and behaves exactly as expected at all times - tried driving hard, throwing quickly into bends, redlining the engine, short-shifting and labouring it, all seem to make no appreciable difference.

Mind says wheel bearing, but then why can't I feel anything different through the steering wheel, or when hard on the brakes?

I'm not hugely familiar with the drive shaft arrangement, but are there bearings in there which could cause a noise like this?

Any experience would be greatly appreciated.

Soaps

i had a similar sound in my Volvo which also had 18" wheels and it was just some stones caught between the brake caliper and disc, maybe worth popping the wheel off and checking?

Agreed. The other possibility (maybe not so much with the Octy 2?) is a loose exhaust heat shield or broken bracket.

I had a similar noise, only lasted for a few minutes, happened as I approached a friend's house at the end of an unmade road. My first thought was the exhaust had come loose and was dragging on the ground, but the exhaust was fine. He popped into my car so we could go for a short drive to try and work out what it was, and as we reversed out of his drive it was still there, but it went as we pulled off. It suddenly came on and suddenly went - the only thing I could think it was was a stone caught behind a brake disc/caliper shield - I would check this first.

I had a 'grating' noise last autumn on the Octy. I looked and the car as I was sure something was dragging under the car. This went on for a couple of days, when I finally got home I started to take the wheels off to find the problem.

Pure luck I took the N/S front off first and found the problem. The inner wheel arch liner had come away from the inner wall and was rubbing against the tyre / suspension.

The strange thing was I could see the mark where the screw had been securing it and the screw was still in place. How it became detatched I don't know.

Hope your problem is something simple like this.

Also check for a stone caught between the coils of the wheel spring - happened to me once with similar symptoms.