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Hey guys...

anyone knows where this noise come from? It sounds like a compressor...this high tone - making me crazy

Hmm sounds a bit dentist drill. Could be turbo or secondary air pump

That sounds like the turbo. Can you hear the high tone noise after you have changed to a new exhaust, I see you are selling the MTM exhaust in your signature?

@Ian...No - no noise changing after exhaust change on this tone...Turbos? Sure? Because the tone is exactly getting high & low with the rpm - don't matter if I drive or not.
Always the same...Yes - MTM is for selling...

@Kent...how to test if it's the sec air pump?

Sorry for my english

Try turning off the AC. Difference?

@Ungjaevel... I tried that - no difference at this noise...

BTW.: My AC is always off...(winter)

But 10 min. ago I turn the AC on and the noise get louder...so what do you think?

Could be a worn bearing on the alternator or air con compressor.

The problem with leaving your air con off all the time during the winter is that the compressor seals can dry out causing leaks. Best to switch it on at least a couple of times a week.

Terminator wrote:Could be a worn bearing on the alternator or air con compressor.

The problem with leaving your air con off all the time during the winter is that the compressor seals can dry out causing leaks. Best to switch it on at least a couple of times a week.

This

People often turn their A/C off during winter as they think it only works when it's hot. A/C filters the air, even when using the heater, plus it stops the windscreen from fogging up by also drying the air. Fuel/power savings from not using it are negligible.

So u think the noise is coming from my AC compressor? Any solution for that?

You need to take it to a competent, preferably Audi experienced mechanic to get the problem officially diagnosed.

It may be possible to rebuild the compressor if this is the problem, rather than have to buy a new one, which is not going to be cheap!

Try to diagnose the source of the noise with a "hear probe". It's a metal stick that you can hold on to different parts to hear the vibrations. Hopefully it's just your alternator, because dismantling the AC compressor means a lot of work..

I guess you have checked that the sound is not chaning when you turn the wheels? (i.e. the powersteering pump)

@Quattro_RS6 - the source is from the left side...and no changing sound by turning the wheels...

Sounds like either Alternator or tensioner/idler pulleys... i have a slight whine from my P/S pump but im not worried, changed the fluid and its quieter so when it gets really noisy i'll replace it.

@TomRS - hope so you are right...but the noise is getting louder when I turn on the A/C :/