NeilW

My '05 C2S also has the popcorn maker / cement mixer sounds for the first 30 seconds after cold start. I thought it may have been caused by the exhaust fixings having rusted, allowing gas to escape from joints in the system until everything heats up after a short while. But, the air pump mentioned above sounds plausible.

cvtbenhogan

Is this noise from the timing chain before it adjusts? Have the rattle on cold starts only and goes away in 30 seconds.

Racetwin2

I have also heard about the hydraulic valve lifters in other Porsche foras. Some people solved it by running the engine with lower oil viscosity which I think is not the ideal solution since it can have other negative effects since it lubricates less when engine is warm. The air pump I have never heard or read about before.

The only noise I have when cold starting my 997.1 S with permanent sports exhaust is the rattling noise from the exhaust which I assume was from the richer fuel mixture. Almost same effect you get when engine braking with the sports exhaust. There is no noise when engine is started when already warm.

I guess it is less likely but if it is none of the above things - Could it be the timing chain tentioner that is not functioning properly?