Humming noise on rolling gear

[MarkyBoy]

Hi all, C250TD 1998 model.

It has developed a humming noise at speeds above about 30mph which gets louder the faster you go. It's something on the rolling gear as it makes the same noise when coasting. It does not sound like a wheel bearing rumble but more like very loud tyre noise (it's not tyre noise, they are fairly new) or bad road surface kind of constant hum.

Any ideas what could be casuing it, it sounds like it's coming from front of car but hard to tell exactly as the noise fills the whole car!

 

[davidsw]

Engine under tray ? Wheel arch liner ?

 

[MarkyBoy]

Thanks, I checked the wheel arch liner and engine under tray, that's all fine

 

[brandwooddixon]

**n.y.m. you've already mentioned tyres***

I was going to say worn tyres, but you've said that they're relatively new.

Have you jacked up the car to see if there is any bearing play or felt vibration?

 

[Steve@Avantgarde]

Suspect rear diff or prop bearing I would say.

 

[MarkyBoy]

Prop bearing, could be a possibility as it has had a slight whining noise for about a year now. The whining stops when free wheeling but the humming is constant. Does that sound likely?

 

[Corned]

Either a bearing somewhere, or are the tyres directional ones with an arrow-head pattern?

 

[CRH71]

What you describe is exactly how my issue started out. I'd get the rear wheel bearings checked if I were you - it turned out that my NSR one was shot to pieces, yet the noise (when it finally got worse) was definitely worse when the OSR was loaded.

However, when the noise started, it was a constant rubbing noise, varying with speed and present whether under load or coasting. It lasted 6-7 months like that before getting much worse - quite suddenly.

When was the axle oil last changed? Might be worth doing it again in case it's just old oil causing the noise.