On starting my 1999 A6 in the morning, about 4-5 seconds after the engine starts, I get a horrible squeal from the front engine compartment. When shutting off the engine, it takes about 3 seconds for the squeal to stop. These times are very consistent, so it almost sounds like something that is on a timer switch relay -- like maybe the electric fan? This started up a couple of months ago -- the squeal would go away after a few seconds. Couldn't get it to repeat at the dealer and they were no help in giving me a diagnosis. Then it stopped for a few weeks, and now it's back. Its taking longer and longer before it stops (I shut the engine off, restart, etc. Takes about 3 or 4 restarts now before it is quiet.)

I live in Louisiana, so it doesn't get that cold at nights. It only happens in the mornings. Or after the car has sat 4-5 hours, and the outside temp is a bit cool -- say 50 degrees or so.

Any ideas?

 

Ok.
Turned off the climate control and the noise doesn't start. So it is likely the air conditioning compressor. I'm wondering low freon level would be the culprit? Would appreciate any advise on the probable course of action to fix, before taking it in.

 

Turning off the climate control should also turn off the auxiliarly electric fan. So you may have a problem with that. If your freon is low the ac compressor wont turn on so thats not it. You could have an ac comprssor or compressor clutch that is noisy thou.

 

I would try to isolate the sound by sequencing the following items:
Eliminate the compressor and associated belt by turning off only the AC compressor.
Eliminate blower fan by varying the blower fan speed.
Try putting dish washing soap on the belt and see if it is just the belt slipping on the compressor.
The AC fan should run if the engine is in the on position with all AC controls set to cool and that would run both the condensor fan AND the blower fans.

 

I have similar issue with my 2000 A6 2.7T 6sp, but I have no expertise to diagnose. My squeeling is not coupled with start up or shut down, tends to be when going uphill. Pretty sure it doesn't effect power getting to wheels, but its worrying me. Trying to get mechanic to find problem, but I think he is hoping it just fixes itself with time. Seems to be increasing.

Mike