I took my 89 911 out for a short drive tonight. Didn't push it at all -- rpms no higher than 4,000. After about one hour, when I stopped at a light, I heard what I can best describe as a low squeaking sound coming from the engine. I got out of the car in a parking area, and sure enough it sounds like it is coming from the top part of the engine compartment toward the back seat. I am no mechanic, but I never heard this noise before, including when I first started the car tonight. Anybody out there have any idea what this could be? Any thoughts are appreciated.

 

Alternator belt?? How much deflection do you have at the, with the motor off?
Steve

 

Steve, I'm not sure I understand your question about deflection. Could you please clarify? Thanks.

 

push on the belt in the middle with your thumb - then post how much the belt is moved in or deflected by the thumb pressure

 

if your belt for your alternator is too tight, it will destroy the bearings in it and will cause a quite horrible noise, it can also cause your fan to contact the magnesium fan housing at the bottom, you will see it all scuffed up where the blades would be rubbing., other than that, there really isnt anything else that I can think of that would make a squeaking noise (unless the engine shrouds are making a metal-to-metal contacting somewhere in back.

 

Yet again, I have had the same problem with my SC (I'm not alone, at last!!!)

It turned out to be the pulley half that was coming loose due to badly placed shims. The pulley had actually started to shatter itself and had wrecked 3 of the shims in the process.

Buy a new pulley half, 6 shims and end nut and your problems will be sorted.

 

I agree with Wayne. Check all the parts carefully if the shims aren't really flat and happy they will squeak.
You MUST have the proper pulley wrench to get the nut tight enough.

 

As Randwebb described it. Push on the center of the belt with your thumb an post how much it will push down from an imaginary straight line ie, 1/4" 3/8", 1/2" etc.
Look at the following link for a picture of deflection, though the site has nothing to do with Porsches.http://www.fantech.net/fade_tabe_thdab_ins.pdf

According to my Bentley's Manual, defelection should be about 5mm or 0.2 inches. Make sure your belt is in good condition and obviously replace it if old, dried, cracking etc. These are not expensive.
Regarding the pulley and shims. The shims that are not used between the pulley halves (to losen the belt tension) must be placed under the retaining nut on the outside of the back pulley half. Do not put them in you rglove box etc. You MUST **Always** use all 6 shims. The pulleys, shaft and shims are designed this way.
regards Steve

 

Thanks to all who responded. I knew I could count on this board for advice. I will check first chance I get -- probably next weekend when I get the car out again. I will let you know what I find.

 

1. check it while sitting w/engine off

2. re-read people's posts above -- it is not a good idea to drive it until you address the problem - risky if it is what we think it is