RRTEC

I am getting a loud groan ( not like a rattle but sounds like accessory belt whine but deeper) at the first start up of the day. Won't donit again unless it has sat for more than 7 hours. Also it is not very consistent. I just left the car sitting for 8 hours and started it and it didn't do it. ( was going to film it)

Car runs really well, no crazy symptoms and the noise goes away in less than 3 seconds. Almost sounds like when a belt driven air compressor tries to crank in the cold.

I have had cars with timing chain rattle (bmw's and a mustang gt) and I dont believe this is that.. It sounds like rubber not metal or plastic.

5CHN3LL

It's hard to guess based on the description - but I'm going with the air injection pump. All in.

OP, this pump is used to help the catalytic converters work more efficiently when the engine is cold, which might explain why it only happens when the car is not warmed up.

If it always does this @ first start of the day, you could disconnect the pump's electrical connection and see if the problem is still present.

ltusler

Could also be the started drive not retracting quickly enough.

Ahsai

If it sounds like this, it"s your starter.

RRTEC

Not nearly that extreme or loud and more muffly. I'll try and get a video tomorrow.

Time4Porsche

I have heard this sound also. I would describe it as a rubber eraser running on a chalk board for a second. Like an air pump or the like. Curious to see what others say - sounds like it comes from under the battery...

Macster

Is the A/C system on when you start the engine?

RRTEC

I have tried it with HvAC on and off with no change.

Rubber eraser in a chalkboard is a good description.

DBJoe996

Loose spark plug perhaps? Once running they heat up fast, expand and seal. Just a WAG

RRTEC

Well 4 days and no noise on startup. Stumped.

Macster

You have to, well make that should, get the car inspected. Get it on a lift and check the water pump for leak sign and the serpentine belt for signs of wear/sharp edges. You can remove the belt -- after you have carefully noted the routing and the direction the belt runs in so you can reinstall it the same as it was before you removed it -- and check all accessory drives for excessive bearing/shaft play.

The start up noise can be a dragging starter overrun clutch. My Boxster was making this noise sometime back but I haven't heard it for a long time, several months maybe more. But it is getting a bit cooler again here so maybe the noise will reappear.

A bad AOS can make a noise or in some cases it can cause extremely low pressure in the engine crankcase and the RMS (or the FMS) can let air past and this can make a noise.

The loose spark plug offered up by DB996Joe can't be overlooked either.

911searcher

It's like that abdominal pain that goes away as soon as you make a doctor's appointment.
One Post on RennList. *POOF*




Did you give it a bit of gas when you started it ? Sounds like it. (Guessing you didnt). Cool recording. Very helpful for others.

CarlOrton

Ahsai, Thank You SO Much for posting that video to ID the screeching sound as the starter. While I'm not the OP, just this AM my new-to-me (3 days!) C2 made the same sound. I was immediately thinking IMS bearing.

I feel much better now!

Carl

Arne Klinge

Do you experience this sound in any weather, wet and dry?

I had this on my former 996, I replaced the serpentine belt with one from the brand Continental. Which is a highly regarded brand in Europe. Started noticing that when raining or damp it started making noise on start-up. When I pull out of my driveway I need to manuver a bit causing some more water to hit the belt, making it squeak again. This did not happen when the motor was warm even during rain, only when cold.

CarlOrton

Arne, if you meant "me", then, no, it was not damp or wet. Just first start, for 1 second.