I am no mechanic so I am not too good at diagnosing what the sound I'm hearing means, or from where it's even coming from.

My 2000 1.8T TT has a 134,000 miles on it. The last few weeks, it's been doing something very peculiar: the first time that it is turned on during the day (or after sitting around for a long time without being turned on), a loud, deep hissing sound will occur at the front of the car, somewhere deep into the right side of the engine, I think. Now, if I turn the car off and turn it back on, it will not hiss, nor will it for the remainder of the day. It is strangely consistent; it always hisses the first time and then acts like nothing is going on the second time.

It sounds serious to me and I'm contemplating getting rid of this car. At the same time, my instrument cluster needs to be replaced for the 4th time, and my fuel gauge is broke for the 3rd time.

Anyone have any idea as to what is going on? Thanks in advance.

 

I know that after mine has sat for awhile and i start the car there is a motor sound like a pump that kicks in and the car revs a little higher at first but was told it was the battery being charged.

 

Well, I have the hiss too, but it hasn't been problematic for me so I've ignored it.

As for your instrument cluster, Audi got class action sued for defective clusters, but 2000 model year cars aren't covered under the class action. I've heard if you annoy them enough they'll just say F it and make you only pay for the instillation, not the part. Like 300 bucks at the dealer.

The pump is more than likely the SAS (Secondary Air System). It kicks on to help start and warm the motor up, then closes and the idle drops to normal.

Hope I helped somewhere :P

 

Its the alternator..... Doesnt effect the car whatso ever.

 

It can't be anything normal. It's never made this sound before. I'll make a recording and let you guys hear it.