Porsche-O-Phile

Weird noise - car has been doing it for a while. Here are the symptoms as I can best describe them:

Intermittantly I'll get a rattling noise (sounds an AWFUL lot like a heat shield, but I checked and they all appear to be tight). It seems to happen only when the car is warm (operating temperature, running a while) not when cold. It also is much more prevalent when the car is juuuuuust starting to build boost - as I'm building it, the noise will happen just as the boost gauge swings through the 1.0 - 1.2 ish range, then usually disappear.

I don't think it's really hurting anything (seems to be running okay - no other symptoms).

It's just annoying as the noise is one that can occur with some regularity even with "normal" street driving - I don't have to be really romping on it to have it happen.

I got under the car and shook the heat shields and pipes - nothing obvious. Maybe it's that enormous catylitic heat shield, but all the bolts are there and it seems pretty secure - maybe it's heating up and expanding or something?

lart951

I had a car with almost the same symptoms and the headers were cracked.

TRP951

same thing happened to me and the starter heat shield cracked the bolts were tight but it had a huge crack in it.

Charlotte944

Are you sure the engine is not leaning out (running lean) as boost builds? That "rattle" could be detonation (ping, knock).

Porsche-O-Phile

Pretty sure it's not leaning out. If anything I suspect it's a little on the rich side. People on drives behind me say that I shoot a little bit of black soot under heavy load, so I'm fairly certain that's not it.

How would I check the headers? I inspected them visually but see nothing wrong.

I'll check all the heat shields again.

R.B.

Check your engine oil for metal shavings. My "rattle" came at a certain RPM and turned out to be rod bearings a couple of years ago.
-R.B.

Porsche-O-Phile

Scary thought. . .

Nope I'm fairly certain it isn't that. I just changed the oil last week and although it was dirty (I'd waited a bit too long) there was no metal in it (thankfully).

Scootin159

A catalytic converter that's breaking apart (due to age) will sound like a rattle. In my case though it's heard more at idle than at a specific power band, but I certainly could see an increase in exhaust gasses causing some type of harmonic turbulance in there.