Any ideas on the cause of this mysterious squeaking sound

[amcleod1]

Hi all,

I have this mysterious squeaking sound that comes from the rear of my 996 only when braking to a stop and only when car has warmed up.

Occasionally I think a can hear a squeak or two when idling.

Any ideas on what it might be ????

Note: There are two runs in this 20sec video - first at walking pace, then second from traffic pace.

[Loren]

Take your polyrib belt off and check each of the pulleys for wobble. Replace any that wobble.

Do the same with the water pump pulley - again if there is wobble then it WILL fail. So, if it wobbles then replace it.

[judgejon]

I had a similar issue. HIgh pitch squeel coming from rear end somewhere. Idler pulley near alternator needed replacement. easy fix. good luck.

[wvicary]

This a manual or tiptronic? It does sound like a water pump to me though.

[amcleod1]

Hi -

Thanks for the suggestions so far.

I will look for the wobbly pulleys after the Xmas holidays as I was planing a 120,000km service in January anyway.

Bit more info on the car itself: 996 C2 MY2000 TIP RHD (Australian).

[amcleod1]

Hi...an update....

I pulled the polyrib belt and checked all 8 pulleys for wobble. No wobbles whatsoever.

I'm open to further suggestions on the cause or other diagnostics I could try to isolate ?

Thanks in advance for any ideas here.

[Loren]

And if you start the car without the belt? (briefly) any squeaking?

[amcleod1]

Hi Loren - I was thinking about that but since the squeaks only occur when the car is at normal operating temperature I was hesitant to try that as no water would be circulating ? I can make it let out a squeak or two every time, when hot, by releasing the brake pedal, letting the car roll forward and hit brake again. Would it rule in/rule out anything if I did same in reverse ? Alex.

[Loren]

Does it never squeak at idle or reving (not moving)?

[amcleod1]

Hi again Loren, I would say no it does not squeak when idle (engine hot or cold) or when revving.

However, some more, squeak test results:

All with A/C off and PSM on.

Does NOT occur when engine COLD, at idle, when revving or whether braking in fwd or rev directions. However, there is some rear suspension "creaking" (but not the same "squeak") noise - more noticeable when car is nose level and down than nose up.

Does NOT occur when engine HOT, at idle, when revving.

Does NOT occur when engine HOT, when braking in reverse direction nose level, or nose up.

DOES occur when engine HOT, when braking in fwd directions, both nose level and nose down, and in both drive and neutral.

Squeaks and creaks more noticeable on the drivers side (remember this is a RHD car) and seem deeper/fwd in the engine bay than the belt area.

I'm now starting to wonder if its rear suspension or exhaust movement. Perhaps "creaking" when cold and "squeaking" when hot. Or maybe its both - i.e 2 separate problems.

Alex.

[fpb111]

Almost sounds like tires talking. Does it make the noise when braking with the engine off? How about on wet road?

[amcleod1]

Hi fpb111,

Ok, I'm curious. I've not heard that term before....what does "tires talking" mean ?

Also to brake with engine off, I assume I'd place the tip into neutral first then switch ignition off and then brake.

As to the wet road - how did you know I just detailed the car !!

Edited January 4, 2011 by amcleod1

[fpb111]

Tire talking = Little moan- chirp while braking accelerating.

Ign off, key on so that ABS PSM etc still active.

The right front tire on a GMC Safari van that I had would do that on every stop after it warmed up. It turned out to be the ABS activating on that wheel only?? I pulled the ABS fuse everything (brakes) worked fine and it stopped making the noise . The van had 180K miles on it and needed too much $$ to make it right so I junked it at the end of that summer. Never did spend time figuring it out.

[amcleod1]

Hi All - an update - I think it's fixed. Not quite sure what the cause was as I just replaced the spark plugs, AOS and a leaking vacuum canister. One of them seems to have been the cause. I suspect the leaking vacuum canister.

[Chris_C]

i had a similar issue with my 2000 911 as well... similar squeeking when the engine was warm allthough i noticed it most of the time when the window was down while sitting at traffic lights

After months of chasing the problem it ended up being one spark plug half way off... did you notice any that were too easy to get out by any chance? haha

[amcleod1]

Now that I've had time think about it - I think you're right - it was a loose spark plug. I was surprised how little effort was required to remove 1-2 off them. I also think the leak in the vacuum canister was the cause of my intermittent P1128 error - will need to drive for several week with no errors to be sure.

[phillipj]

Had the same issue with my first 996 a few years back... Took it to the dealer and they told me I may be looking at a new engine.:cursing: Wasn't going for that......

Luckily I went on this site and someone with the same issue had posted a sound clip. Same sound as mine. His diagnosis? A loose spark plug. Sure enough one of my plugs was loose. Problem solved.... Glad you got it fixed!

:renntech: