Grumbling/whirring noise - any ideas?

[stroberaver]

Yesterday, following a 20 min journey in the afternoon in my 2004 Ibiza FR, after dropping a friend off to come home I noticed a nasty whirring/grumbling sound coming from the car. At first I thought the worst and that it was engine related, but soon established that the noise was independent of engine speed & load, and gear selection. The noise, however, is:

• speed-related. No noise when stationary, at it's worst around 30-40mph, and fades away above 50mph.
• happening going forwards and backwards
• slightly worse under low-speed braking as you come to a stop
• not audible first thing this morning when I set off to go to work and the car was cold. However after 5 mins of gentle stop-start driving it became detectable, and after 10 mins (when I got to work) it was back to the same as yesterday.
• is more audible inside the car with the windows up, than with them down and listening for noises outside.

Any ideas what I should look for? I thought some debris might be stuck in the brake but there's no sign of any scoring on the disc, and the noise goes away at higher speed when surely it would get worse. I feared wheel bearings but wouldn't have thought this would account for the lack of noise when cold or being able to hear it inside more than out. Plus, the car is only just coming up to 50k miles! (yes, I have a short commute!)

Any suggestions as to possible causes are appreciated. Typically, I was looking to take some time off work in the next couple of weeks and do a little road trip - wouldn't dare risk it until I can establish and resolve whatever is causing this noise!

[stroberaver]

doogz said:

I'd go with wheel bearings as a first guess. They might not be noisy when they're cold because the grease is more viscous at that temperature, and when it heats up and thins, you're hearing the rumbling.

Jack the car up and give the wheels a shake, see if they're tight or if there's any play.

Kinda hard to diagnose something like this without hearing/seeing it, you're going to get a thread full of guesses.

Cheers, hadn't considered that about the grease viscosity. Done a bit of wading through flood waters this summer too, wonder if that's affected the bearings. I'll be jacking the car up at work today and having a test. I know my suspension bushes are shot which currently gives some play in the front left suspension, and they're actually being replaced this week with better bushes from the Cupra.

I don't mind some guesswork here, any ideas welcome as I struggle to accept that wheel bearings can/should fail after less then 50k miles - especially since most of those 50k miles are gentle stop-start journeys on 30mph roads on my 10-15 minute drive to work, not as if it spends it's life blatting up and down crumbling B-roads giving the wheels and suspension a hammering. :-/

[stroberaver]

Wow, never realised wheel bearings could be such a lottery, based on some of the experiences here.

Thanks for all the help and comments. I'm still confused by mine though, and wondering if it is the wheel bearing. Never got a chance to jack it up yesterday as I ended up being stuck in meetings all day at work. Set off from work yesterday to come home, and the grinding noise was worse than ever, right from cold. But I noticed that it would stop for a split second when the suspension was being compressed - particularly when driving over a gentle trough in the road surface as the car climbs out of it and the front suspension compresses, or over the vicious speed bumps in the supermarket carpark. In fact after stopping at the supermarket on my way home, upon resuming my journey the noise had stopped completely and everything was back to normal. At this point I noticed a groove scored into my right front brake disc that wasn't there a few days ago, and figured there must have been some debris stuck in the brake after all.

Set off to go to work this morning, and the noise is back, but this time it's intermittent and now dependent upon steering angle (but not wheel load or weight transfer, as we're talking low-speed maneouvring). Almost no noise when straight ahead, but plenty when turning left.

It seems so inconsistent. I'll have to ask the garage that it's going to for new bushes if they have any rollers they can stick it on when I drop it off to help diagnose the problem.

[stroberaver]

Well I forgot to reply to this topic at the time, but I did indeed take the wheels off and rummage about. Everything sound - nothing loose, broken, or sounding rough.

Then while the car was jacked up I spotted a small branch (or very, very large stiff twig) about 2½ ft long wedged into a chassis member near the middle of the car and pointing forward, hanging down. Took some effort to yank it out, after which the noise vanished, so rather embarrassingly, it appears the branch was dragging on the road and resonating into the chassis or floorpan at just the right frequency to make a horrible grumbling wheel-like noise.

Still, glad it's nothing expensive.

[stroberaver]

4key said:

Excellent, thats going to be my new standard answer to random noise questions

Yup, check for trees under your car.

It was going to the garage later that week for upgraded console bushes anyway... thank god I'd sorted it without the embarrassment of asking the garage to diagnose what was only a vegetation-related noise.