DesmoSD

This sounds like your cats. This happened to my buddy's 996 after a track day at California Speedway last month. 2003 996 C2 with about 60K miles on it.

This happened when he returned from his second to the last session. Once he pulled into the garage, there was a ticking sound that was echoing inside the garage and enough for him to notice. He immediately shut it down and started to look around for any possible signs, oil, coolant expecting the worst.

He eventually drove it home since there wasn't any performance loss and it went away when he started driving. It was more noticeable at idle and if it was near a wall or parking garage. Back in SD, he brought it to several shops and eventually brought it to Black Forest. That's where they pinpointed the issue to a bad cat. The screen and materials inside broke down from heat and probably time.

mikemessi

It's no GTS but my 2011 997.2 Carrera has the same constant quiet ticking with the sporadic louder ticking similar to yours. It has come and gone since new and now has 45k miles. I always attributed it in my mind to the complex valvetrain of the 9a1. This is a clip from 2009 Porsche press release.

JPM_GTS

I appreciate all the information guys. What a great community we have here!!

ADias

Those ticking sounds are not valve sounds.

nwGTS

agree

gasongasoff

Oh goodness, I had the EXACT same noise and pattern on my 997.2S. I only heard it when the car was idling. It would get a lot worse (louder and more frequent) after driving at least 45 mins, and then listening to the idling engine again (without turning it off). I posted it here, and you can listen to the audio (along with all the engine parts that were replaced until I finally got a replacement motor for Porsche).
https://www.6speedonline.com/forums/...can-t-fix.html

JPM_GTS

[left]did they ever tell you what the issue was on your old engine?

mikemessi

And when they installed your new engine did they use the original cats? I have a hard time believing its the cats as others have suggested.

bhvrdr

You can rule out the cats/exhaust by simply shutting off the engine. If the tinking noise goes away when you shut off the engine its not likely the cats/exhaust as they will continue to make clanking/popping noises with engine off.

mike

JPM_GTS

Just found your previous post about your ticking noise, does it sound the same as mine? Was it different incident? you mentioned EVAP PURGE SOLENOID and not the belt tensioner.

JPM_GTS

You're right as soon as the engine is off the noise is gone.

mikemessi

Exhaust metal expansion and contraction ticking continues after shut down but loose cat cells bouncing around from exhaust pulses does not. Just because it doesn't continue after shut down does not rule out cats. Non the less this does not sound like loose cats to me.

DesmoSD

What else do you think it can be?

That sound that you're describing is normal for a healthy cat. All cars w/cats make that sound after you turn off the engine for several mins.

I showed your video to my buddy with his 996 and he said it sounds similar but not rhythmic as yours. Since CA law is strict with any emission device, the shop couldn't do any aftermarket cat replacement; only OEM. He ended up buying Magnaflow cat and had a muffler shop across the street install it. When he showed me his old cat, the screen was broken and pieces of metal could be heard bouncing around like change in a tin can.

Again, others say it's not the cats but my buddy was driving his 911 at a higher pace, similar to your situation when the cats went out.

Frank996

mikemessi

Hitting the cat with a rubber mallet will usually reproduce the sound of loose metal in a can which sounds different than the sound in video. I have no idea what the sound in the video is. Like I said mine has done this as long as I can remember and I attributed to valvetrain. But an ancillary such as oil pump, hpfp, belt tensioner, etc makes sense too. Interesting mine is heard at the same location (loudest at right rear underside). From what I understand there are multiple electronic oil pumps operated on demand by the ecu. Since the sound comes and goes and seems to be an odd rhythmic, could it be one of these oil pumps going bad? Other thought to me is a chain tensioner losing pressure at idle but I would think that would be more continuous.