I have 2008 C2S Cab 997.1. I had this random noise appear after I replaced a serpentine belt. Dealership has been trouble shooting the noise for over 15 days. First, they replaced the serpentine belt and said i've installed a faulty belt. The noise went away temporarily and came back after 3 days. Went back to the dealership and after 13 days they replaced two idler pulleys and claim the noise went away. I came home today and the noise came back. Anyone have this similar noise issue?? Please share your resolution!

 

If I read your post right the noise isn't present at cold engine start but shows up some time after?

Noises are hard enough to diagnose in person and from a distance one can only really hope to be lucky.

One needs to be sure where the noise is coming from.

If from the accessory drive area it can be a bad belt -- usually bad because of some other problem -- or an accessory drive idler/tensioner roller bearing is bad.

Yet another source of noise from this area can be a noisy accessory drive, noisy due to excessive shaft/bearing play.

Actually my admittedly limited experience in this area is any play is serious grounds for suspicion of an accessory drive. Thankfully one has several to check and the one with the play almost certainly has to be the bad one.

Regardless of which accessory drive is bad a telltale is the belt will develop a sharp edge because it rubs against a pulley wall. The belt is not intended to touch the pulley walls. Unlike a V-belt which relies upon its V-sides to drive the accessories the serpentine belt works strictly by contact of its inner surface against/around the crank pulley and accessory drive pulleys. A serpentine belt with a sharp edge is a sign the belt is not tracking true and this is because of play in accessory drive.

Now, most often the source of the noise is the water pump. Sure there are exceptions: With my Boxster just within the last month or so it started making a noise out of the blue -- not present one minute present the next -- and after some professional (Porsche tech) effort with nothing found wrong the diagnosis was that road debris/trash somehow got caught in the accessory drive system and just as mysteriously got free, probably when the car was on the way to the dealer on the back of a flat bed tow truck. In the case of my Turbo two times now an accessory drive idler roller/tensioner roller bearing became noisy and I had all of these replaced. (The ones on my Boxster are original and with over 309K miles.)

I would have thought the tech when he had a chance would have checked the accessory drives for any signs of play. I mean even as a non-professional shade tree mechanic I can't walk by an engine with its accessory drive belt removed and not give the accessory drives a grope/feel for any play.

Based on the audio in the clip listened to at the office with a noisy A/C vent overhead my guess would be the noise is from the accessory drive system and because all the idler/tensioner rollers have been replaced the noise is from an accessory drive (water pump, power steering pump, A/C compressor) and is due to too much bearing play.

That reminds me: The power steering fluid level has been checked and found OK?

Does the noise depend upon the A/C being on? The snowflake symbol on the LCD control panel being lit?

My advice would be to as quick as you can learn how you can reproduce the noise and arrange to then get the car on a lift with the noise present and so a pro tech can give a listen -- a good one should have at hand a mechanic's stethoscope -- and pinpoint the source of the noise. From this then the tech should be able make the final diagnosis.

If he finds the noise coming from inside the engine that's something different. It doesn't sound like it to me but I'm not the professional and I'm not at the car.

 

Thank you for your insight Macster!

Your absolutely right on the noise not being present at cold engine. The noise appears after the engine is warmed up. Once its warmed up, the noise is consistently heard. The noise is not dependent on A/C being on or off and I will check the power steering fluid level as soon as it is time to leave the office. I can't quite figure out where the noise is coming from but I often see myself leaning more towards the left side of the engine compartment to hear it more clearly.

I am going to go see a local shop that works on Porsche and see if they can lift the car and identify source of the noise. Already sourced out belt/idler pulleys. Thanks for the troubleshooting approach! Is there an easy way to check if your water pump, power steering pump, AC compressor is bad?

 

Additional video for diagnostics! This came from Porsche Dealership.