BobbyT

I'm getting a screech/squeal noise that occurs just on start-up for a second or so. I thought it was the alternator failing, so I replaced it. No joy.

The belts have about 20,000 miles on them. They are all correct Porsche OEM, and the tension is correct when checked with the Krikit tool.

When the belts are removed, the fan and alternator each rotate smoothly and easily. The fan blades are not contacting the housing.

The noise is still there with the fan belt sensor removed.

Any ideas on what to check next?

John D.

I would change the belts anyway - because if they are glazed - it will happen..? Since the alternator is new - it's not the bearing..??

Hmmm..???

John

SC2993

That's what my belts did just before disintegrating! Only on start up and when very cold.

Mike J

Have you tried a belt dressing yet? I find that sometimes works.

Cheers,

Mike

TheOtherEric

I'd have to guess belts.

Stealth 993

Mine does it after she gets a bath, it's the belts.

BobbyT

Thanks, John,
I was thinking the same thing, but before I do that I think I will just remove the AC belt and see if the noise goes away. Maybe the AC compressor is getting ready to pack it in, rotational resistance is getting higher, and makes the belt slip just a bit on start-up. I'll let you know what I find.

BobbyT

Okay, it's not the belts, or anything related. I removed each belt in turn, and then started the engine briefly after each removal, but the noise persisted, even with AC, fan, and alternator belts gone. The noise is a screech/squeal, about as annoying as sharp fingernails on a chalkboard, and seems to come from the top center of the engine, forward of the alternator. It lasts just a second or so. SAI pump? HELP!

Side benefit, I think I can change these belts blindfolded on a galloping horse.

BobbyT

Is there a way to disable the SAI pump temporarily to see if the noise goes away?

Stealth 993

Blown SAI pumps sound like a high pitch whistle, or a screeching type noise.


If you wait 2min the pump shuts off, or if you have a Durmetric cable you can turn it off & on on demand. You can even turn it on with the engine off.

cabrio993

maybe the steering pump and/or belt? Belt is ribbed, but worth checking...

It's right next to the SAI valve and close to the general area where you hear the noise.

Boeing 717

My Car does it too but i just put brand new belts in. I figure they just need to be tensioned some.

BobbyT

I don't think it can be the power steering pump belt. Isn't it unlikely to make a noise when the car is still? More likely to make noise when the steering wheel is being moved? Also, the location of the noise seems to be more in the center of the engine, not on the right side, where the PS pump is.

wolfgang1

I had that problem too... for me it was the fan roller belt.

http://p-car.com/diy/roller/

BobbyT

I removed the fuse for the SAI pump (as well as the relay), noise still present. So far I know it is not the fan belt sensor, not the belts, not anything belt-driven. This is a puzzle...