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My S4 has suddenly started making a horrendous knocking/grinding noise which seems to be coming from the offside front. The sound varies in intensity, so it sounds like a woodpecker one minute and the noise you hear whilst on a train as it passes over the rails the next. It also seems to come and go depending on whether I'm accelerating, braking or coasting - there's no consistency to it. I can actually feel the knocking very faintly through the wheel and pedals when it's at its worst. The car drives OK and steers, brakes and changes gear perfectly normally but clearly something is very wrong. As soon as I can I'll take the front wheels off and have a look for anything obvious, but for now does anyone have any ideas what this might be from my description? Suspension/brakes etc. are all standard.

Cheers
John

Sounds like a dry CV joint.

Or knackered wheel bearing

Thanks guys. My first thought was wheel bearing but someone else has also suggested CV joint so I'll get this checked out as soon as I can.

It's being looked at today and the technicians are fairly certain it's the wheel bearing. Fingers crossed!

Get the wheel of to have a look.
Maybe a stone behind the disc/heat shield?

I thought that too, but a mate and I already had a thoroughly good check underneath with a torch before I booked it in. Everything looked perfect, with no obvious play in the bearing or anything - very weird. I'll know more tomorrow...

All fixed. It was the wheel bearing after all; apparently the inner race was "pretty rough" and this was causing the noise.

I'm a bit surprised that a wheel bearing can go at <38k miles but there you go - I'm just relieved it wasn't something more serious.