I recently purchased this 2004 Audi S4 with 4.2L. It had some minor issues and needed some tlc, so I replaced both intake camshaft adjuster solenoids since one had siezed, resealed the timing covers, replaced valve covers and valley pan gasket, replaced some leaky hoses and fittings, replaced the alternator belt, and flushed/changed both the coolant and the oil.

Now, after the car gets warmed up, it makes this intense high pitched whine.

On a cold start, there is no noise. Engine sounds/runs great. Once the coolant temperature reaches about 140F, the whine starts suddenly and doesn’t stop until either I shut off the engine or create a large vacuum leak. Removing the oil cap will make the noise much quieter, sometimes it will make it stop. The suction on the oil cap feels normal. I checked the PCV valve, even removed it completely and blocked the intake tube, but it has no effect on the noise. If I give the gas a quick rev, the whine will stop for a half-second, and then continue. If I run the car until the noise starts, and then shut off and let it cool down all the way to 100F, I can start the car and the whine will be present immediately. The noise seems to be resonating throughout the engine so it’s hard to locate the source, however it seems to be loudest from around the throttle body/ rear of the intake, and at the front of the intake.

Any bright ideas?
Thanks in advance

 

is there no way to delete a post/thread?

got it solved - scratched intake surface, tiny leak