I am getting a high pitch whine noise at idle after driving the car. When I start the car it isn't there. When I rev the car up to 2-3k rpms it still isn't there (thought that might eliminate the turbo *crossing fingers*). When I drive it for any amount of time it seems to show up as soon as I idle (not hearing it when I drive or accelerate...again, hoping that eliminates the turbo). It almost sounds like it has a cadence...like it's electrical (?).

I didn't notice it until I took it in to the dealer for the coil pack recall. I thought that it was probably a vacuum leak (I am throwing the code 17887 - Brake Boost Vacuum System...will be replacing all the braided hoses soon) but the tech said that he thought it was the oil cooler because that is where he heard the noise coming from with his stethoscope and apparently didn't hear anything from a vacuum hose. He also said that when he reached down and grabbed the oil cooler that it stopped. I haven't tried that myself yet but I will tonight.

My question is, does it seem probable that it would be the oil cooler causing that sound? And if so, what might be the reason? Any explanation would be appreciated.

I am putting in a new thermostat in the next month or so and I know that the oil cooler is right there (2002 A4 18.T) so I could change that out at the same time but would rather not spend the $100 on the oil cooler (plus an oil change, etc) if it isn't needed.

Thanks for yout time.