Hey guys, newbie here, have a 1998 A8. Just bought it, pretty cool car, but needs some minor jobs, such as front rotors, track rod ends etc... and I can handle those, but the problem I have is a (fairly) random noise coming from the interior fan... when the car is cold, and, only sometimes, immediately you turn the interior fan on, it makes a loud 'groaning' noise, that is not subject to engine speed, or fan speed. It goes away either if you just leave it on, or if the car gets warm. sometimes when you turn it off then immediately on again, it clears.... is it maybe plastic on plastic rubbing somewhere?

help please!!

 

It's actually an exterior fan, under the hood at center of fresh air plenum. I went by the Bentley manual and it was pretty easy to get to with basic tools. Mine just needed a little spray grease in the bearings (bushings?)...all quiet now.

Or could be a little foreign matter (leave, stick, etc.) rubbing the fan cage and makin noise. Even though it's kind of a sealed system, it's amazing how many little things can get in while the hood's up. I cleaned out gobs of little leaves and sticks under the fan (against the AC evaporator), while I had it apart.

 

thanks buddy, can you help me out with a more specific location please? because it's random, i haven't managed to tie down the location yet, is it under that plastic/mesh cover in the centre up by the firewall, between the engine and the windscreen?

Thank you so much, I figured it was something like that, but couldn't work out where...

Paul

 

Below is a good link I found to show exact location and disassembly...BUT before you go diggin in that deep, you might want to try "blowing it out" if it's just foreign matter and not the fan bearings. Manually set fan to highest speed and go through all the vent settings: just floor, just defrost, just frontal (middle), etc... one at a time, then alternate recirculate and outside air.
Worth a shot, just in case it's something small that you can break loose (?)


http://www.audipages.com/Tech_Articl...anreplace.html

P.S. Just noticed you mentioned that the groan does NOT change with fan speed? That's a little odd (but not impossible) with a fan problem. Could also be one of the many flap control motors (don't know how loud they could be...I can hear mine faintly, making changes during normal operation). Groan may go away because a flap breaks loose from stuck position (?). If this is the case, you might narrow it down by taking vent controls thru their paces as mentioned above (esp while groaning is present), with fan speed at low level so you might hear it more clearly...again, worth a shot.

 

Fantastic, what an excellent reply. Thank you. Will try this and keep you posted..
Paul