Exhaust rattle, leak or whatever it is - it's annoying! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

njbray · 02-08-2015, 10:02 PM

Car sounds like a VW Beetle! Trying to figure out if it is a leak or cat. rattle.
I know it is quite common and would appreciate other peoples ideas, what to check, where to look, etc.
Thanks.

rdass623 · 02-08-2015, 10:07 PM

look around all the seams in your exhaust. if there is a black residue, you have a leak. if you tap on the cats with a rubber faced hammer, you may hear some rattling if the elements in the cats are breaking loose. best bet is to get the back end up on some ramps or stands and go to town checking everything..

bwillia080261 · 02-09-2015, 08:56 AM

Mine does that too. It sounds like a leak at the exhaust manifold gasket but I have had my Indy look at it and so have I. No luck.

nieuwhzn · 02-09-2015, 09:47 PM

Check the heat shields on the cats, they tend to start sliding around. Once in a while I have to hit mine with a hammer.

Nimbus117 · 02-10-2015, 08:28 AM

Both 02 sensors were loose on the LH pipes when I bought the car and rattled on overrun Also one of the hangers had fractured on the back box which wasn't easy to find plus of course, rattling heatshields.

Was fair to say, the exhaust was definitely not the best (unlike the rest of the car).

Jschindler · 02-18-2015, 10:04 AM

My 99 started making an exhaust leak sound under load. I found the leak at the flange before the Cat on the Drivers side. I'm going to try a new flange gasket from Pelican.

If you find that you have the same leak, the Part Number is 996-111-113-02

Jager · 02-18-2015, 06:35 PM

Gravel in the catalytic converter heat shields will cause a rattle sounds at various RPM’s… It’s very annoying. I removed my heat shields, no more rattles.

njbray · 02-18-2015, 07:17 PM

Joints & heatshields seem ok. I think maybe the rattle is coming from one of the cats.
When I whack it with a rubber hammer it rattles. I need to get some ramps so I have more room to look. When I get my wife to rev it it doesn't rattle! BUT when I go to drive out the garage - of course - it rattles!

Jschindler · 03-30-2015, 10:05 AM

Quote:

Originally Posted by Jschindler

My 99 started making an exhaust leak sound under load. I found the leak at the flange before the Cat on the Drivers side. I'm going to try a new flange gasket from Pelican.

If you find that you have the same leak, the Part Number is 996-111-113-02

I hope this helps someone. I replaced the gasket mentioned above, but it did not change the sputtering sound I was getting. I tried smoke testing but found nothing. Started the car on a lift and found that the drivers side pre-cat joint was still leaking very slightly. I let the car cool and laid a bead of silicone window sealant around the leak. Let dry over night and that made all the difference in the world. Car sounds amazing now. When the silicone fails, maybe it won't, I will pull the header and get it welded up right.

Diagram below shows where I put the silicone in white.