X51

Anyone else experience this? My dealer's techs say it's normal. I'm not so sure. If I accelerate and let off the gas or engage the clutch to drop the revs, you can hear it. You can also hear it when accelerating through that rpm range. Sounds like a loud buzzing/metallic rattling sound - not a banging sound, just an annoying buzzing. I know it happens in 1st, 2nd and 3rd. I won't load the engine in 4th or higher to see if it does it.

Other experiences, thoughts, ideas welcomed. Thanks.
Kurt

Rocco07

I've had his in another car, not a Porsche. But, I discovered it to be a cracked exhaust heat shield. The buzzing had a "tin like" kind of sound that occurred only in a certain RPM range. May I suggest inspecting the heat shields specifically the more solid sheet metal types that may be around the headers (if we have them). The flexible ones around the exhaust mufflers may not be the culprit, but I'd check those as well to be sure they're not in contact with anything that may produce the buzz. To fix the car I experienced it with, a muffler shop repaired it with a simple weld. It was done with the shield in the car. That may not be the case with the 911.

X51

Rocco07, that is exactly the sound it is making. I had the heat shields off for a muffler upgrade and had the sound before and after the install. I inspected the shields and tightened everything down - still have the sound. I don't recall seeing any stiffer heat shields near the headers.

Rocco07

The stiffer ones may be above the headers protecting components, and may not need to be removed for mods. The crack may not jump out at you. You may have to flex things a bit to expose the defect.

Edgy01

Do you notice this after the engine is hot, or when cold/cool?

I discovered a crack in my exhaust system and it was resolved under warranty. (Do a search)

X51

It's when the water temp is up to operating, but not the oil temp. So, I would say as soon as the engine is "warm" to "hot" it is most noticeable. I can feather the accelerator between 2600 and 3000 and drive myself crazy with the noise.

What part of your exhaust system was cracked, and do we have heat shields around the headers? I did not see any when I was last under my car, but I wasn't directly under the headers - sort of a 45 degree angle to the tops of them.

Thanks.

Edgy01

The area that was broken or cracked were the bands that secure the muffler components together.

X51

Thanks, Dan. Taking it in Friday to have them listen to it and get a diagnosis if possible. Will post what they find.

joeljackson

Ever get any resolution on this?

I'm having the same issue.

J

Renzsport

I had this happen on mine - cracked exhaust brackets/bands. It seems almost common with PSE, although yours doesn't look like it has PSE...
Had them all rewelded and no more tinny buzzing!

X51

No resolution to mine. Dealership put the acoustic ears all over it and couldn't pinpoint it. I spoke with Darin at FD Motorsports about trying a replacement pair of sport mufflers, but I haven't tried that yet - still trying to narrow it down.

holden997

I suspect it is the dual mass flywheel. Porsche had this problem in the 996 and I believe the 997 DMF are similiar.

http://www.pelicanparts.com/techarti...chBulletin.pdf

Papa Fittig

Do you hear the sound if you just rev up to this RPM range in neutral? Or is it only happening while driving? If you can reproduce it in neutral, try to locate the sound source. My first guess would be exhaust, like others suggested. If you can reproduce it while engine is cold, you can try holding exhaust to see if this would change the sound or eliminate it.

X51

Not the DMF issue on mine. No tranny noise, no rattling, no clunking, no knocking. Metallic, raspy buzzing is what mine is about.

That's a good technical bulletin for that issue, however.

MagnusB

Go figure. I have a broken exhaust bracket band in just about the same spot.
This noise has been driving me nuts for a while now.