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Ericson38 -- I took your suggestion and got someone to hold the revs at 3900 and 4600 RPM, and got a video of the sound... I think you might be right about the resonance of a metal part. From inside the cabin, it sounded like a hissing or vacuum sound, but from outside the car, it's more like a high pitched rattling or squeaking. AND more data: it's not loudest in the engine compartment, it's loudest in the area around the right exhaust tips/right exhaust.
Here's a video. Sound stops at 0:04, and starts up again at 0:07. It's that squeaking/tapping/rattle noise.
Chicagospeed -- I was on your wavelength about the airbox, and even ordered up a new air filter to replace before I went and shot this video. Imagine my surprise when I shot the video and found out the sound was nowhere near the airbox!
Originally Posted by Ericson38
From the rear, are both exhaust tips at the same height ? Looking for a sagging motor mount that could change a clearance to the chassis in the exhaust system, thinking that it is a resonance of something not in the engine, but connected to it, made out of metal.
Ever get an opportunity to have someone go through that RPM band with their foot in neutral while you listen from the back, possibly under the car (on a rack) ?
Metallic hissing from 997.1 S engine bay at 3900 RPM?
I had mine in for an oil change today, and there was a ticking noise that I thought was lifters, but sure enough my Indy found the hydraulic belt tensioner was toast. The tensioner was covered in oil. Cost was $500 including parts and labor. Now that I'm a little more in tune, but far from an expert, couldn't that sound in your video be your belt flapping? Again, I'm no expert and could be way off.
I'd remove the exhaust tips and see what happened, or with an asbestos glove you might try grabbing the exhaust pipes one at a time and see if you can find what is squeaking, or it could be an exhaust leak mimicking a squeak or, I give up.
Good theory, except the mechanic also had serviced the tensioner and the sound is still there. But an unrelated, annoying creaking was stopped because of the tensioner service! Haha
Originally Posted by rjshar
I had mine in for an oil change today, and there was a ticking noise that I thought was lifters, but sure enough my Indy found the hydraulic belt tensioner was toast. The tensioner was covered in oil. Cost was $500 including parts and labor. Now that I'm a little more in tune, but far from an expert, couldn't that sound in your video be your belt flapping? Again, I'm no expert and could be way off.
I almost absentmindedly grabbed the pipes as I was filming the video... That would have been dumb. But I like your thinking; it does make sense that the exhaust system is making that noise since the sound doesn't occur until the engine (and exhaust) is at operating temperature (which for my car is 225 degrees).
Originally Posted by gpjli2
I'd remove the exhaust tips and see what happened, or with an asbestos glove you might try grabbing the exhaust pipes one at a time and see if you can find what is squeaking, or it could be an exhaust leak mimicking a squeak or, I give up.
This is really good stuff...... my 2009 Technical Introduction manual does not go into that much detail.... it outlines the valve lift but not the cam timing component... which is in the DFI engines. My manual just notes it but does not go into it.
I need to study this a bit as I was blaming the suckout on the valve lift... could be something else. Although the few Porsche techs I talked to about this over the years all say the thing should throw a code if it even burps... which it doesn't.
The rattle is the exhaust tip connection. Is it more pronounced when u turn AC on (more load on engine)? If u search my threads I started, I have thread dedicated to this issue. You will need to find which side/one is cracked. Then need a welder. It's heat changes over time that causes cracking.
Turn the car on and don't rev it. Just put in neutral. Next turn AC on. Is the rattle increased when AC applied? May have to have someone turn AC on off for u while u listen from back. And the car should be warm like after a 10 min drive. Then it should act up. "Exhaust tip rattle" is my thread. Page 2 is most relevant.
Thanks to everyone for their great suggestions... niner niner seven wins the prize for guessing the correct issue! Turns out it was a cracked exhaust bracket, the one welded between the two exhaust pipes on the right side of the car. Put the car on a lift this morning and while I revved to 3900 and 4600 RPM, my mechanic isolated the problem, then he hit it with some welds. BINGO! Noise is now gone.
FYI -- My rattle didn't get worse when the A/C was one, and it seemed to be the same no matter what the engine load. It only came on at exactly 3900 RPM and at 4600 RPM. Hope this helps someone who has this problem in the future.
And now that this is fixed... I can hear more rattles inside the cabin that need hunting down. Haha
Video of the sound as the mechanic was troubleshooting (sound starts at 0:07, a little bit like a radial saw):
Looking forward above the exhaust tips, that is the bracket that broke loose.
Welding the sucker down.
Originally Posted by niner niner seven
The rattle is the exhaust tip connection. Is it more pronounced when u turn AC on (more load on engine)? If u search my threads I started, I have thread dedicated to this issue. You will need to find which side/one is cracked. Then need a welder. It's heat changes over time that causes cracking.
07-30-2015 | 08:21 PM
