BMW Repair: E46 Rear Exhaust, bmw 330i, vacuum line

Question
Hi Evan,

I have E46 BMW 330i Auto, 2000 model. There is a flap in the rear right tail pipe of the exhaust. The problem is that its not closeing/opening as it should. Its OPEN ALL the time. I would appreciate your thoughts as to what could be the cause of the problem and what part may need replacing. Also if you could explain what the flap does?

Many Thanks
Harmit.

Answer
Harmit, this flap is for European regulation of exhaust noise. Why they put it on U.S. models I don't know. There is an vacuum line that runs from the engine and applies vacuum to close the valve below around 3000rpm. Check the vacuum line. If the valve is broken you need to replace the muffler if you wish. The valve is sprung open without vacuum. I would put a Golf tee in the vacuum line and tie it back. This devise has no use other than to reduce noise. If it is rattling or causing noise then replace it. Please fill out a follow up survey if this helps you.
-Evan