Strange rattle

[shiversaint]

Hi, long time lurker and have finally bought a 2008 2.0 GT Roc which generally I'm pretty pleased with. Previous owner Blufin'd it.

I have a weird rattle that isn't a windscreen one or any of the common ones, and I'm 98% certain it's not wastegate either. This is what I've determined:

- It is essentially not present or inaudible under 30mph
- It then gets louder and louder the faster you go, being really bloody loud at around 80-90. It also feels like it gets a bit faster in frequency as you speed up but not by much.
- You can lightly feel it through the steering, although the wheel does not wobble if you remove your hands whilst it is happening, so I think it's just general vibration here. Turning quite hard at speed makes the rattle more consistent in frequency
- You cannot feel it through the gearbox/stick and it is there irrelevant of clutch in or out. As the clutch "bites", it goes away momentarily. It is therefore unaffected by engine speed.
- It disappears under all acceleration
- It disappears under braking
- It's just gone through a MOT with no advisories from what I know to be a strict garage - I'd think something like a wheel bearing would get picked up here?

So essentially, over 30mph, when coasting or not accelerating. Fairly sure it's from the front of the car, and probably drivers side. I have had the front offside driveshaft replaced to no avail - garage said there was a small bit of play so we assumed that was it, sadly no dice. Given the way it responds to braking and accelerating, I don't think it's a loose control unit in the boot nor does it sound like it's coming from there.

Does anyone have any ideas? I'm going to try and record it tomorrow. Many thanks in advance.

[Cuprabob]

Check your tyres.

Sciroccos suffer from abnormal tyre wear (sawtooth / treadstepping) on the rear and it possible the previous owner has rotated them to the front. It's not something an MOT tester is likely to pickup.

[shiversaint]

I'll go and have a look in a minute - in truth it sounds a lot more "mechanical" than what I'd expect from something like that....

Also if memory serves, the car had new tyres less than 10k ago. They are a cheapy brand though.

[Cuprabob]

It was when you made reference to the wheel bearing which when failing rumbles and drones, which is exactly the same sympton the tyres give.

[shiversaint]

Fair enough. Yeah this is definitely more of a knocking rattle. Almost like the thud of a cricket ball hitting a cricket bat. At high speeds, it happens 3-4 times a second. I referenced the wheel bearing just because it strikes me as something rotational. Road surface also doesn't seem to matter and hitting a pot hole doesn't result in a louder bang.

[daves2369]

Possibly check your driveshafts for any damage and CV boots for anywhere where dirt could of got in?