996 Screeching sound

[mhariush]

I recently got a 99 996 and every now and then I hear a screeching sound when I accelerate from standing still. It's not constant and sometimes it's louder and longer than other times. It's not there most of the time.

The best way to describe the sound is: The sound of a chair being dragged across the floor

Any idea what this could be? The car has manual trans and 106K miles. PO replaced the IMS bearing (LN Engineering) and clutch last January.

I'm not too worried about it, but it's not a nice sound.

Thanks

[996 TT]

Please check this article, may be it could help you, Pelican Porsche Tech Article - IMS Bearing Replacement - Porsche 911 Carrera - Porsche 996 Carrera (1998-2005), Porsche 997 Carrera (2005-2008)

[mhariush]

Thanks, but as I said above:

PO replaced the IMS bearing (LN Engineering) and clutch last January.

That's perhaps 10-12K miles ago. And this was a reputable shop. House Automotive

[LanceGT4]

My 99C4 has a clutch on the alternator.
could this be causing the noise?
I think it supposed to let it freewheel on engine decal but if the one-way mech. is going it might be slipping on accel.
at least it a maybe.

Anyone know how to check it?
Luck

[mhariush]

The sounds comes and goes. But I had my brother sitting in the car this past week and it sounds like the sound is coming from the rear and more specifically from the rear wheels... Possibly the calipers sticking?
The sound tends to come when the car is warm, but it's very random. And trying to recreate it is very hard.

[Long Nose]

And you are sure it's not the tires?

[LanceGT4]

I almost forgot about something that has happened to me.

On my '99 C4 I got what sounded like the brake lining had fallen off the pad and I had metal on metal contact. It's happened more than once.
Turns out that the gravel DOT uses instead of sand is just the right size to bounce up between the rotors and the weather guard on the backside of the rotor. Once it's in there the guard acts like a sounding board.
Not quite the sound you describe but try stopping and rolling slowly backward. Maybe you'll get lucky and have a passenger that can get out and listen for where the noise is from.

Once I had to take the wheel off and use a piece of Alum TIG rod for a probe to wiggle it out.

First time this happened was before I replaced the O-rings in the spark plug tubes.
Went screaming down the on-ramp and as looked in the mirror I saw smoke and a gawd-awful screech from the back of the car.
The noise didn't stop until I hit the next off ramp and found safe spot to check out the heck was going on. Rolling backwards cleared that one.

[LanceGT4]

Brain farts today
How are your parking brakes?

[FPB111]

Also check your accessory drive belt.
Or change it if you don't know when it was last changed.
While you have the belt off spin all of the pulleys to check for, noisy/loose/rough bearings.

[Zmonsta]

I have a similar problem for about 3yrs now, but mine is still with stock IMS and clutch on a 99.

Mine always goes away once the engine warms up, but can be reproduce for a very short time if engine cool down just a little, but goes away again once warm. Also it happens even with accessory belt off (so it's not any auxiliary pulley).

I'm interested in this thread and how you will resolve it. I have read that sometimes a slightly loose spark plug can cause this, something to look into (I haven't had the chance and won't get to climb under it until around Mid-July).

Good luck and keep us updated please.

[mhariush]

I'm going to pull the belt and replace it and the idler/rollers/pulleys too.

Zmonsta: It's weird that this sound keeps coming and no one knows where its from... Mine seem to come when the car is warm(er), never on cold starts.

I had a really loud long one and I think I felt it though my shifter...