Strange exhaust noise when engine is hot - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Compass1 · 06-03-2008, 08:27 PM

Hello all, this is my first time on this site and I need some help. I have a 2003 Boxster S (great car). It makes a buzzing rattling noise coming from the underside of the car on the passenger side. This noise seems to be coming from the exhaust pipes. It is especially worrisome and loud when I back off from the throttle at low speeds. I had the 'heat shield' tightened, but that did not fix the problem. Any incites as to what it is and how I can fix this problem. Regards. Compass1.

Brknbonz · 06-03-2008, 09:21 PM

CHECK ALL YOUR CLAMPS, AND SUPPORTING BRACE TO YOUR MUFFLER. LOTS OF NUTS THAT POTENTIALLY COME LOSE. Also CHECK THE LOOSENESS Of ANY ALUMINUM HEAT protection UNDER THE ENGINE. Does THE NOISE OCCUR UNDER NEUTRAl with just revving the engine? Or is it just when driving?

06-04-2008, 03:51 AM

The cats might be damaged.

Boxtaboy · 06-04-2008, 03:58 AM

I had a rattle from my exhaust area only after the car warmed up. Turned out to be a loose clamp that connected a U-tube from my cat to the muffler. The U-tube would move slightly when I shook it. Tightened it up, and no more rattle.

When the car is cold, grab onto every single exhaust part and shake it to see if anything is loose. That's how I finally found out my problem.

It could be a bad cat converter, but not as likely IMO, because you would also probably get a CEL light if that were the case.

dj1 · 06-04-2008, 06:11 PM

Hate to be cynical, but I'd bet on a bad cat. It can be really difficult to isolate the rattle, I know from experience,and there are lots of ways to temporarily muffle it, but if its the cat the only permanent fix is a new one (and it's worth it). Good luck.

dcporsche99 · 06-06-2008, 01:09 PM

Hey Compass1,

I had two areas of vibration similar to the one that you described. For the first one, I ended up putting a large screw-type hose clamp completely around the heatshield (re: after having tightened all possibilities to no avail) and that was able to do the trick.

The second vibration came from an aftermarket header that was abutting the variocam cover w/c I was able to creatively muffle using exhaust wrap and two screw-type hose clamps.

Good luck and let us know what you find.