relinuca

Recently, during a three week cold snap, my beloved '99 (67K miles) has developed a very noticeable squeeking noise on cold start up.

Once the engine warms a bit (i.e., when the temp needle moves slightly upward), the noise progressively disappears.

FYI-the noise is an upper frequency metallic sound, almost like a finger nail scratching on a black board, and definitely is keyed to engine rpm.

Water pump? Belt tensioner pulley? What say ye...and don't scare me too much as I have yet to pay off Christmas bills!

relinuca

PS: I took the car to my p-car dealer. Of course, the noise refuses to re-appear while in their hands.

Macster

It is best if the techs can hear the noise. Did the dealer leave teh car outside or in the shop?

If you want to get your hands dirty....

Remove the belt. If you are going to reuse it -- if it is original replace it -- note the direction the belt rotates so you can install it the same way.

Also, note the routing of the belt. Take pics.

Then with the belt removed start the engine and under conditions you are sure the noise has appeared before. No need to let the engine run any longer than what it takes for you to confirm the noise is there or not.

If the noise is not present install the belt and start the engine.

What you hear or do not year determines what you do next.

About the belt. Check it while you have it out of the car. Any sharp edges? This can be a sign the belt is rubbing and my experience is it rubs because an accessary drive has excessive bearing play.

My experience is any play is excessive. You can walk around and test each accessary drive for any play and note all are free of any play so if one has some play, even a tiny bit, that drive has to be suspect. Odds are if you find an accessory drive with any play it will be the water pump.

Check the belt for missing sections of its v-ribs. Cracks across the v-ribs are ok but missing sections are not. The belt should be replaced.

Check the idler rollers and tensioner rollers for any excessive play or roughness. Examine them carefully for any signs of bearing or seal issues.

Steve's MLC

Great post Macster. I didn't know you could start the engine without the belt on. I assume this means that none of the accessory drives have any timing or link issues with the motor?

Byprodriver

Yes that is correct. Of course the belt drives the waterpump so you have maybe 5 minutes before the engine heat could be a problem.
I believe the 997 plastic pulleys have replaced the 996 metal pulleys so opportunity for upgrade to lighter faster pulleys.

Macster

Yes, you can start and run a cold engine without its serpentine belt.

The serpentine belt has nothing to do directly with the engine's ability to start and run, at least idle.

Now some engines have a rubber timing belt and this can't be removed and the engine run. It will not run, for starters, but it will in fact be damaged when cranked because the valves are not moving in sync with the pistons and valve and piston contact will occur.

As an aside: You can start and run a hot engine without its serpentine belt but for far less time than you can run a cold engine. You can even run the cold engine without any coolant for a few moments. I drove my Boxster a few blocks after it sat overnight sans any coolant -- lost it all after I hit some road debris and busted the radiator -- from its parking spot on a gas station lot to the Porsche dealer down the street with no harm.

There will be no water circulation, the battery will have to supply the electrical power, and there will be no power assisted steering.

If the battery is borderline it may not have enough juice and the engine can act erratic, warning lights can come on, etc. which is scary but harmless. Still you should err on the side of caution and turn off the engine and get a stronger battery or diagnosis the problem another way.

When you remove the belt you want to make sure you note the direction the belt rotates, its routing -- take pics or make an accurate sketch do not rely upon your memory -- so you can reinstall it correctly or install a replacement belt correctly and of course do not damage the belt taking it off or putting it on.

luvmy911

This is a helpful video showing how to remove the serpentine belt on our 996 cars:


Hope that helps.

Pac996

My best guess for out of the blue noise like that is like above, the belt. I wouldn't try belt dressing after seeing what it does on a jeep. Lots of goop and can make the noise louder while gumming up the pulley's.

carcster88

If the belt looks OK, belt dressing if fine to try.

relinuca

While not absolutely sure, the Tech and I suspect the water pump as the culprit. Close enough! Replaced it, if for no reason other then peace of mind.

relinuca

kpl

idler pulley probably...mine had the same symptoms. It also made a racket when really hot. Easy to diagnose and replace yourself. When the belt is off it'll be the pulley that is obviously more difficult to turn by hand.

Barn996

Did the noise go away?

relinuca

In re. barnes996' question...No, the noise is still occurring under very cold start-up conditions.

We're about to receive a blast of freezing rain and some snow. My "plan" is to wait for a repeat of the right climatic conditions and then squirt some water on to the belt. If that stops the noise, then the belt would be suspect. If not, I may replace the tensioner pulley. I'm still mulling things over.

relinuca

Capt. Obvious

My car does something similar to this when it's been raining/washed. I've traced the noise to water leaking through the engine cover onto the serp belt causing it to squeek.

washington dc porsche

Are you sure it isn't that pump next to the coolant tank?

Viper6

I get this same condition right after washing it, goes away when dry.