Grinding noise while coasting. Gearbox or wheel bearings?

[Ved]

Tonight my MKV Golf R32 started making a very nasty noise and before it goes into VW for an inspection I'd like to know what you think.

Car:

51k
FVWSH
No recent knocks and only just serviced.
Driven generally only on long distance
No fast and furious gear changes etc

Problem:

Inside the car when coasting below 40mph there is a hollow grinding noise. It's metallic but still quite a low frequency noise. I suspect it's always there but just masked by higher speeds.

The noise is related to the speed of the wheels and I can only hear it from the drivers side.

If I use the throttle, regardless of RPM, then the noise goes away.

Outside the car I can hear a squeaking noise which matches the frequency of the grinding noise. Imagine getting an irate and indestructible mouse caught in your tyre tread. This noise again goes under load.

If I coast around a roundabout the squeaking noise on the drivers wheel quietens down. I can't tell too well if this changes the noise inside the cabin but I 'think' it did.


Thoughts?



David

[Camaro]

Try finding a couple of bends you can coast round. If you can relieve the noise or reduce it going one direction and increase it in another, I'd stab at it being a wheel bearing.

[deltashad]

Uhu... wheel bearing... had one on the 'gay car' before its last MOT.

[Ved]

Camaro said:

Try finding a couple of bends you can coast round. If you can relieve the noise or reduce it going one direction and increase it in another, I'd stab at it being a wheel bearing.

Thanks mate. That's the test I did around the roundabout so fingers crossed it is the wheel bearing. Normally they've sounded like a very bassy and dull noise but this is metallic.

Fingers crossed!

[falkster]

Ved said:

Thanks mate. That's the test I did around the roundabout so fingers crossed it is the wheel bearing. Normally they've sounded like a very bassy and dull noise but this is metallic.

Fingers crossed!

But if they've missed out the dull stage and gone straight to metal shagged bearings then it could be gone noise.

When you say coasting, do you mean totally out of gear or foot on clutch?

[sunbeam alpine]

Could also be worn brake pads? Metal on metal?

[Ved]

falkster said:

Ved said:

Thanks mate. That's the test I did around the roundabout so fingers crossed it is the wheel bearing. Normally they've sounded like a very bassy and dull noise but this is metallic.

Fingers crossed!

But if they've missed out the dull stage and gone straight to metal shagged bearings then it could be gone noise.

When you say coasting, do you mean totally out of gear or foot on clutch?

Good point. Both, out of gear, in gear with no load and also clutch in. Tickle the throttle and the noise goes away.

[falkster]

sunbeam alpine said:

Could also be worn brake pads? Metal on metal?

Wouldn't that have been picked up on the recent service?

[Dogwatch]

falkster said:

Wouldn't that have been picked up on the recent service?

I wondered about brakes when I read the OP's description. Depends how thorough the 'service' was I suppose.

Bearings don't usually 'grind' unless they are really, really shot.