Squealing sound coming from engine compartment

[gogotodorov]

I have a squealing sound coming from the engine compartment.
When the car is started from cold there is no noise. After approx 15 min of driving (car up to normal operating temp 180-190) the squealing starts barely noticeable at first. After that squeal intensity increases until it is always there regardless of throttle position. It changes in pitch and intensity with engine load/rpm.
The squeal is present when moving and when stopped at idle and with or without belt. Also, squeal is not affected by clutch position, engaged/disengaged.
I have replaced the AOS and J tube but squealing still remains. This did not solve the problem and I am out of ideas. The car still runs well with no noticeable loss of power even when noise is present. Car idle is good, oil and coolant levels normal, and no fault lights are on.
Car is a 1998 with 70k miles. I am out of ideas on what to check. Looking for suggestions. HELP!!

Thanks,
Here is a sample of the noise:
http://www.youtube.com/watch?v=MJ8K7H_JWlg

[paulv]

Here's something I found that may help you:

http://www.import-car.com/Article/85317/tech_tip_porsche_m96_engine_screeches_during_warmu p.aspx

BTW, there's been a TSB out on this issue for a long time, so I was surprised that it was described on this site.

Regards,
paul...

[Topless]

Some more ideas:
Squeek sound upon acceleration from slow speed?? what is it??

The TSB PaulV linked to may also apply but it looks specific to a 987 and not a 986.

[monaghana]

Saw this on another forum not sure if it helps.


"Hello, I found out the true problem why my belt was squealing, my radiator fluid resvior was leaking right on the belt. As soon as i got a new resvior and changed the belt again, no more squeal so check to see if your resvior is leaking. my mechanic checked my pulleys and belt tensiors, plus he even checked the timing belt tensiors too. So if your radiator fluid is constantly low and you have to refill it every once and a while. It may be leaking, my leake was a very slow leak and it leaked directly on to the belt.

[gogotodorov]

Thanks for your suggestions friends, but the noise is there even with the belt off. So it's not from the belt. It appears it's coming from the cylinder head behind the passenger. What could it be ?
Any ideas ?

[jcb986]

Yep, had the same thing...it's your AOS. When the AOS starts to fail it will suck air through the front crank seal. Had a Porsche mechanic tell me that and I thought when it failed you got a lot of blue smoke from the engine. Replaced the AOS and have had no problems since.