Last 2000 miles my MK6 fiesta has an increasingly loud road noise. At 30mph it can be heard and gets worse up to 70mph. Its loud enough to be difficult to speak to a passenger.

Done the generic wheel bearing check and jacked it up and spun each wheel and they all seemed fine. Tried jacking up front right and left wheels and running the car to about 2000 revs in second gear. The right wheel makes the whine but the left doesn't under the same conditions. I'm not sure how to check if this is wheel bearing, diff, gearbox or anything in between.

Does anyone have any ideas of what it could be or how to check?

5 hours ago, Brieznt said:

Done the generic wheel bearing check and jacked it up and spun each wheel and they all seemed fine. Tried jacking up front right and left wheels and running the car to about 2000 revs in second gear. The right wheel makes the whine but the left doesn't under the same conditions. I'm not sure how to check if this is wheel bearing, diff, gearbox or anything in between.

On these modern bearings, unloaded tests (wheel off the ground) will reveal, usually, nothing. It needs the weight on it. I have a failed bearing from my car, it feels perfect until pushed hard in a certain direction, then there is just a tiny roughness. Undetectable on the car while stationary, but really quite loud when driving.

Diff & gearbox whine will be very torque dependant. On a long downhill, try putting it in neutral, see if the noise changes. If not, it is probably not gearbox or diff. Though you could also check the oil level just in case.

Centre driveshaft bearing remains a possible. Best test for this is weaving. You need a nice, dry, straight road, not too much traffic, about 50mph. Then carefully but positively weave from side to side, staying in your lane. A change in tone on each side of the weave will indicate a wheel bearing. Most likely to be the one on the outside of the bend, but this is not 100% certain.

I had both my front bearings go in the last 15 months, that was the identifying test. Though it was 2 or 3 months from first detecting a whine to being able to hear the change clearly on a weave. Cost me £450 for the pair, 12 months apart.

Bends in the road can also be used, but changes in surface texture and the time interval between changes of direction make the weave method much more positive. But do not overdo it, or you could end up in the ditch, or worse!

 

 

+1 for driveshaft support bearing , jack the offside wheel up and spin slowly while feeling the bearing cap for a grinding type feel 

Thanks guys. 

Ill give it a check using those methods and see where I get too.