Squealing noise coming from engine compartment
 

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

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...

Some more ideas:
http://986forum.com/forums/showthread.php?t=25242&page=2&pp=20&highlight=chir p

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

Could it be leaky radiator fluid resevoir?
 

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.

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 ?

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. :cheers:

Thanks for your answer jcb986. Are you sure your problem was like mine? (did you watch the video i upload: http://www.youtube.com/watch?v=MJ8K7H_JWlg ). Is it the same noise? I have replaced already the AOS because i was hoping it causes the noise but - no luck.. still squealing :( .
Somebody with the same squealing noise ?

Most of the common sources discussed here. Maybe you missed this thread:

http://986forum.com/forums/showthread.php t=25242&page=2&pp=20&highlight=chirp

Problem SOLVED !
 

Thank you Topless :cheers: !!! The problem was loose spark plug :) .
I'm so happy now ....
Thanks to all of you.

Good news! A loose spark plug is pretty common. Cheap and easy fix too. :cheers:

Sorry...you said squeal not a chirping sound...glad you found it. :cheers:

Engine Chirping sound - loose spark plug, 2002 Booster 986
 

I also had a loose spark plug. Took a while to track it down. Had the car a year now and chirp started a few months ago. I replaced the power steering pump (really not fun) and upper idler roller to no avail. That was before I read on the forum a tip to remove the serpentine belt and run the engine briefly.The chirp was still present meaning none of the things turned by the belt were causing the sound. (alternator, PS pump, AC, water pump, rollers, tensioner). Many on the forums indict the AOS (air-oil separator) but in my case, the AOS was on the opposite side of the engine from the noise, and there is no gray smoke coming from the exhaust; engine runs clean and smooth. Decided to change the plugs and sure enough, one plug was loose enough to turn by hand. Replaced plugs, torquing to 22 ft-lbs and noise finally eliminated. I would never have thought that spark plugs would loosen over time. Thanks all on this thread for pointing me in the right direction.:cheers: