My car is a 2006 Carrera S with about 47k miles on the odometer. Anyone else have this happen? I get a "ssssssss" metallic hissing sound coming from the engine bay as I'm driving ONLY when the revs are at 3900 RPM exactly. Usually I don't notice as I'm passing through 3900 pretty quickly, but if I hold it at 3900, the hissing comes up and holds steady until I move off 3900 RPM.

No power loss, no warning lights, no other noises or other trouble.

It's not a turbo, so it's not that.

The only other thing I did was an oil change about 50 miles ago, using Motul 8100 5W40.

This just started happening so I haven't had a chance to isolate where in the engine bay it's coming from.

Is it the variocam?

 

Vacuum Leak? Possibly a pulley going or misaligned?

-M

 

If the car has an after market exhaust or headers, a hissing noise is common on all sports cars particularly with headers. If it has aftermarket exhaust/headers there is likely no problem with the car at all..

 

No aftermarket headers or exhaust. Bone stock system with factory Porsche Sport Exhaust (with the orange plug disconnected).

 

Well, i think this has something to do with it. You may have a vacuum leak as Hella-Buggin' stated.

 

Oops sorry, totally typo'd that... I meant "NOT disconnected", meaning fully stock and PSE activated by the Sport button.

I'll check for vacuum leaks, thanks all!

 

How does the Varioram system work and at what RPM is the intake length changed? Seems like it might be right around that 3,900 RPM #. Just putting that out there as a guess.

 

That was my first guess too, but I figure a Variocam problem would sound more like a rattle or clunkiness...

 

Serp belt tensioner pulleys?

 

When you do find out what it is please follow up here so we have a good example if it happens to anyone else. Good luck!

 

Absolutely will follow up on this! So the two possibilities so far are:
1) Vacuum leak
2) Serpentine belt pulley

Will be checking on these things next week. Would anyone think these possibilities are serious enough for me to cancel a morning drive through the canyons over the long weekend?

 

I would suggest you stay below 3800 rpm or above 3800 rpm. Of the choices the latter seems the most fun. JKA

 

[Cue Bon Jovi] Goin' down... in a blaze of glory!

 

Any gear, through accel and deccel ?

How about neutral ? Someone run it up in neutral while you listen both sides, under rear wheel house too.

Maybe heatshield touching muffler, or it not completely secured ?

 

This happens when the engine is at operating temperature, in any gear including neutral, and it happens going up through 3900 RPM during acceleration, as well as down through 3900 RPM the other way during decceleration.