Swanson

I'm hearing this mid treble squeal intermittently on start up. It's high pitched, but not as high pitched as the tranny pump squeal (from what I understand). The squeal lasts for only a second or two and is rather loud. It sounds like a belt - the big tip off is that I get the same squeal for a fraction of a second when I turn on the AC. The belts look fine to me, but I don't know what I'm looking for. What else squeals on an A8 on start-up?

A8CT

how many miles? The belt tensioner is a likely culprit if original. If you can rule the belt and tensioner out, then I would suspect the alternator since the load causes the noise too.

Swanson

I'm at 130k miles - rebuilt transmission at 124k. I have no records regarding the age of the belt, tensioner or the alternator, so I'll assume they're original. I'll get out the Bentley, find the tensioner and see if I can isolate the squeal. It happens maybe only 1 in 10 start-ups, and of course, I can't get it to squeal when somebody else starts it up and I'm listening with the hood open.

-OvO-

maybe it's a bearing?

SWiseman

You have enough age and miles that the fan bearings may be going. When you have the A/C on it runs. If you leave the A/C set to auto, the fan runs on startup or when you turn on the A/C regardless of temp. When the fan bearings start to go, it will squeal for a few seconds and stop until the next time you start the car from a cold start. You can check by turning off the A/C when you hear it. If the sound stops suddenly, its the fan motor and you need to look at a replacement.