Porsche Repair: 944 S2 whislting noise, air path, luck dave

Question
Hey Dave,
I have a 1990 944 S2 cab in great condition that has an annoying whistling noise coming from the engine bay.  The sound rises and falls with engine revs.  It is definitely getting louder and I can't locate the source.  Performance hasn't been affected (so far).  Any suggestions where to look?
Mark  

Answer
Hi Mark,

I suppose there are several likely culprits when it comes to odd noises.  You'd think for such a beautiful car, Porsche would have dealt with this issue!

Here are three possibilities:

1.  Alternator drive belt, or really any belt, if it is a tiny bit loose...the sound should be more pronounced with a cold engine.
2.  A whistling could be an air intake issue...perhaps there is a tiny opening at the air inlet, or even along the air path, that is restricted enough to create a whistle.
3.  Early water pump failures will sound like a whistle.  What's happening is the bearing surface is worn down in such a way as to be loose enough to start whistling.  When it squeals, it needs replacing.

Frankly, I'm not sure what you can do when these ideas.  Other than wait til the sound gets progressively worse and then identify it.  Or, while someone revs the engine slighty, you could use the auto stethoscope kind of tool...lay it on the water pump housing, for example, and the sound...if there is any there...should be amplified in your ears.

Good luck.

Dave