2000 audi a4- humming noise coming from rear of car

remove and have the starter bench tested for armature/brushes and solenoid problems

Whining high pitched sound from front end...left front wheel bearing or right it could be hope this helps tell me if it does

The rear wheel bearing on 2000 Audi A4 is adjustable! Very simply to do this work.

I dont think this is a problem. I have the same noise when openning the doors on my 2009 1.8t a4, u might also get this sound when you open the trunk as well. this is probably a manufacturing thing. it could be that the car senses that the door are open so that it would prepare the on board computer for ignition or something of that sort... thats my guess though!! but i believe its normal

Does the humming noise only occur in a certain gear(s)? does it go away whilst changing gear or cornering?

COULD BE THE WHEEL BEARING WORN. JACK THE WHEEL UP AND MOVE FROM SIDE TO SIDE LOOKING FOR EXCESSIVE PLAY AND SPIN THE WHEEL CHECKING FOR ROUGHNESS OR TIGHTNESS IF YOU HAVE THIS ITS THE WHEEL BEARING.....IF IT IS MORE LIKE A CLICKING OR KNOCKING NOISE WHEN DRIVING IT WILL BE A CV JOINT.TO TEST, DRIVE AT SLOW SPEED ON FULL LOCK AND YOU WILL HEAR IT.....IF THE SOUND IS COMING FROM THE ENGINE IT WILL BE ONE OF THE PULLEYS,(TENSIONER OR WATER PUMP) BUT IF IT IS THAT, YOU SHOULD STILL HEAR THE NOISE WHEN YOUR STOPPED (REV THE ENGINE A LITTLE) AND IF THERE IS NO NOISE ITS NOT COMING FROM YOUR ENGINE THEN......HOPE I WAS OF SOME HELP TO YOU..HAVE A NICE DAY.!!!!

SOUNDS LIKE ONE OF YOUR WHEEL BEARINGS HAVE GONE WEST REPLACE THESE BEFORE YOU GO KOOFING FOR A DEEPER PROBLEM

It's the wheel bearing. Guaranteed. Just replaced mine. Go to Audiworld tech articles for step by step instructions on how to test the wheel bearings. They must have been put in wrong last time or they just went out again.

What kind of noise? Is it a humming noise that gets louder as the road speed increases? If so, it's a wheel bearing - A4s eat wheel bearings like popcorn.

Could be a transmission issue. Did you hit any objects while driving ? Have you performed a visual inspection under your vehicle ? Have you checked to see if you have any loose vacuum hoses ? Any codes in your engine control module or transmission control module ?