Cross post from wrong group? 97 A6 Q, Q?

[garydutton]

Hi all,

apologies if this is a duplicate question (I was not able to find an easy way to successfully search archived messages).

I have a 97 A6 Quattro. 85k regular service.

Looking for ideas on a very irritating noise in the passenger cabin. It demonstrated problem for last 3-4 yrs but is getting much worse.

When I first had the vehicle it would occasionally make a high pitched whistle when at certain freeway speeds. The pitch of the noise was directly related to the throttle position and occured regardless of a/c unit or blower operation. If you changed throttle position enough it would go away. The noise was only heard on warmer days.

Nowadays - The noise occurs at much lower speeds and (what is most annoying) at idle. It only happens on warm to hot days and the pitch is still altered by throttle position. It can be so loud now that not even the radio can hide it. The noise still begins regardless of a/c or blower operation BUT... if it is making the noise and I turn off the a/c the noise will stop instantly (for a while). This is also the case even if I have to turn the a/c on in order to then turn it off!

The whine/whistle seems to be coming from the a/c ducting just below the windshield. I have so far spent $600-700 having it looked at but so far with no success. They garage filled the a/c system with smoke and checked for a diaphragm leak... no luck, so they changed the fuel pump! Yeah... what a surprise... no fix!

I'm so close to selling this car for this problem alone... so any ideas much appreciated.

thanks

Gary

 

[audi5e]

The fuel pump on those cars is in the tank under the back seat, so I doubt that was the cause of the noise.
The noise is more likely coming from one of the vacuum hoses that control the aircon system. These are small diameter pipes that control the opening and closing of the various flaps that duct the airflow to the different parts of the system.
Get yourself a hollow tube that you can hold against your ear. Then run the other end over the area you think is the source of the noise. Since it is repeatable at idle you should be able to find it.

If one of those pipes gets a small tear/crack then it will suck air in and cause your noise.

 

[audi5e]

The fuel pump on those cars is in the tank under the back seat, so I doubt that was the cause of the noise.
The noise is more likely coming from one of the vacuum hoses that control the aircon system. These are small diameter pipes that control the opening and closing of the various flaps that duct the airflow to the different parts of the system.
Get yourself a hollow tube that you can hold against your ear. Then run the other end over the area you think is the source of the noise. Since it is repeatable at idle you should be able to find it.

If one of those pipes gets a small tear/crack then it will suck air in and cause your noise.

 

[audi5e]

The fuel pump on those cars is in the tank under the back seat, so I doubt that was the cause of the noise.
The noise is more likely coming from one of the vacuum hoses that control the aircon system. These are small diameter pipes that control the opening and closing of the various flaps that duct the airflow to the different parts of the system.
Get yourself a hollow tube that you can hold against your ear. Then run the other end over the area you think is the source of the noise. Since it is repeatable at idle you should be able to find it.

If one of those pipes gets a small tear/crack then it will suck air in and cause your noise.

 

[audi5e]

sorry about the triple reply, internet browser was not responding so this user went into a mild rage and repeatedly pressed the continue button.