One or maybe more than one of my catalytic converters has started to rattle on 2000 Boxster, real noisy on start up and then quiets down as engine warms up. Is there a way to tell which one it is (the 2000 has 4) or do I have to replace them all? Any ideas on what the dealer would charge for replacing one or all four?

 

I would get underneath with a rubber mallet and hit them a few times. If they are coming apart, they will rattle when you hit them.

 

Porsche Doc,

Appreciate your suggestion, I will try that tonight. Can you think of anything else that could be making that kind of sound coming from the rear of the car? It sounds like a heat shield vibratingand it is worse when engine is cold. Once car warms up, you can still hear it but not as prominent. Am I hurting anything by driving the car with this noise? Again, many thanks for your help. -rPm