Strange exhaust noise when engine is hot

[Adam]

Originally Posted by bmwm750

Correct me if I'm wrong, but aren't the manufacturers required to certify emissions components for 80k? I had both cats replaced on my last BMW at 70k under warranty.

Patrick

Exactly, this should be covererd by warranty if the cats are in fact bad.

[dj1]

The cats aren't technically bad if they pass emissions, even though the rattle indicates they are beginning to break down. The noise is annoying for sure, but it's probably not possible to get the manufacturer to warranty them unless they fail the emissions test. Good luck.

[chaudanova]

I've got a set of brand new Stebro Racing secondary cat bypass pipes available... PM if interested... Thanks