Hi I am hoping you can help me. I have a B class and its started making this whining noise which increases as the revs increase. You can't hear it when at idle in drive but as soon as you set off it gets quite loud. It sounds as though it's coming from underneath the car. No warning light are on the dash but the car doesn't seem to have as much go about it. Also there is a warm smell of burning, kind of like a hot metal smell through the vents. The engine is at normal operating temperature. Any suggestions most appreciated. Forgot to say car has done 147k and it has full service history.