New noise under hood, what is it?
09-08-2008, 06:08 AM
#1
Audiworld Junior Member
Thread Starter
Join Date: Jul 2008
Posts: 80
Likes: 0
Received 0 Likes
on
0 Posts
New noise under hood, what is it?
Saturday morning I was in Northern MN and it was relatively cold when I started the S8 (47 degrees) and I heard a noise in the cabin that sounded like it was coming from behind the dash. The noise sounds like a pump or electric motor running loudly. It's a constant hum. Perhaps a pump is about to fail?
I opened the hood and it sounds like it is coming from the area next to the master cylinder, almost underneath the air box. It sounded like it was coming from the two black cylinders between the Master cylinder and the air box in <a href="http://www.audipages.com/Tech_Articles/heatac/evapdrain9.JPG">this picture</a>.
It's electrical, I can hear it with the engine off and the key in the run position.
I think it has something to do with the environmental systems because if I turn both temperature setting to "Lo" the noise stops, but if I set it even one degree higher it comes on again. I can hear it even if I manually turn the fan down all the way until the lights go out (this is as close as I can find to "OFF" for the climate controls)
Anyone know what this is? I really don't have time to mess with it right now and will probably leave it alone for the time being unless someone thinks this doohickey could damage other components.
I opened the hood and it sounds like it is coming from the area next to the master cylinder, almost underneath the air box. It sounded like it was coming from the two black cylinders between the Master cylinder and the air box in <a href="http://www.audipages.com/Tech_Articles/heatac/evapdrain9.JPG">this picture</a>.
It's electrical, I can hear it with the engine off and the key in the run position.
I think it has something to do with the environmental systems because if I turn both temperature setting to "Lo" the noise stops, but if I set it even one degree higher it comes on again. I can hear it even if I manually turn the fan down all the way until the lights go out (this is as close as I can find to "OFF" for the climate controls)
Anyone know what this is? I really don't have time to mess with it right now and will probably leave it alone for the time being unless someone thinks this doohickey could damage other components.
09-08-2008, 09:17 AM
#5
AudiWorld Super User
Coolant After Run Pump
As in the "rest" feature of the HVAC system, it circulates coolant across the engine to the heater core after turning the car off. It always runs with the ignition on, and then after a while, they make the noise that is descibed.
Unplug it, you no longer have the "rest" feature, but you don't hear the pump as you drive the car. The normal water pump can still pump water to the heater core.
Unplug it, you no longer have the "rest" feature, but you don't hear the pump as you drive the car. The normal water pump can still pump water to the heater core.
