Strange humming noise...

[Linus Van Pelt 0]

I'm not expecting anyone to get this, since it's really hard to describe the noise, but I thought I'd throw it out anyway.

 

I can best desribe the noise I'm getting as a pulsing hum (about 1.5s on, fading out for 0.75s and back on again). The period of this oscillation does not appear to change with the speed of the car. The hum is at a higher pitch than the engine, but it's not what I would descibe as sqeaky or wailing. The noise is only noticeable once the car is travelling at more than 40mph. Putting the clutch in, foot off the throttle and coasting down a hill, the noise is still there. Once the car is at motorway speeds, the sound is drowned out by the engine/road noise, but I'm pretty sure it's still there.

 

(Just to add that I'm blessed with particularly sharp hearing, so it might not be all that loud, since I'm very good at tuning in to noises.)

 

I'd be very grateful if someone has any idea where I need to be looking to find out what's going on!

 

Cheers,

 

DtM.

[Supercharged 2]

Wheel bearing?

[jedi-knight83 0]

i'll second that....my friend had the same thing on his vr6....noise wasnt tied into the speed of the engine or car, etc....off side wheel bearing was the culprit.

[Linus Van Pelt 0]

Thanks peeps. I had my rear bearings replaced recently, fronts were done some time ago now. I think the sound is coming from the rear (but I'm really not that sure), so maybe they did them up too tight?

 

At least it gives me somewhere to start looking!

 

Cheers again,

 

DtM.

[Geo 0]

Yeah they may have been overtightened. Directly after driving the car see if one of the back hubs is hotter than the other. When the bearings are gone the extra friction causes more heat to be generated.

[Linus Van Pelt 0]

Okay, after my drive home (approx. 60 miles), both rear hubs were warm to the touch, there was a slight difference, but it really wasn't that noticable. The front hubs were quite hot to the touch, not hot enough to burn my finger, but not a long way off. Now I know the fronts are carrying all the power and most of the braking, does this mean they should be that much hotter?

 

To recap, the rear bearings were changed in february '04 (approx. 7K miles ago) and I thought the front bearings were last changed back in July '02, but looking at the invoice again, it didn't specifically mention them :?: which means they could still be from when I got the car over 45K miles ago :shock: (and however long before that they were last done)

 

Think I may have answered my own question, but does this sound like time to get them changed?

 

Thanks for the pointers!

 

DtM.