Chris Ferrell

I've read all the posts around similar issues folks have had over the years. And tried most of the fixes people have identified (re-welded muffler clamps, fixed heat shields, replaced belts, accessories, etc over several years) But the noise is still there. I had the PSE unplugged for a few years so I didn't notice it as much. But I'd like to see if I can solve it. If anyone had the exact same noise with the exact same symptoms, I'm curious if you found a resolution.

The rattle is faint, sounds metallic, and starts to be heard as the car warms up. I can't hear it when the car is not warmed up. It's never super loud, but is noticeable. It is only typically heard in first gear at around 3,000 rpm. It may be there in other gears and just harder to hear. Mostly notice at traffic lights and stop signs when taking off from a standstill. It becomes audible when oil is halfway to 200 degrees F and water is around 160 degrees F. Car is a 2006 C2S with no mods.

I recently had the mufflers re-welded. That fixed another noise, but this one is still present. This one sounds consistent, so I'm starting to think it's something to do with the engine or something that happens around 3k rpm. I'm going to change the Oil Pressure Relief Valve to see if that does anything, but I'd be surprised since mine should have the current design.

Petza914

How many miles on the car and have the timing chain tensioners (there are 3 in your engine) ever been replaced? It could be timing chain slap and if it has worn through the plastic paddle that protects the metal guide underneath it that could be the metal on metal sound. Do you check your oil filter at each oil change - you're looking for a hard black or brown plastic. If you've seen any of that, it's time to pull the sump plate and see if there's more of it that has collected in there outside the swirl pot areas or stuck in the pickup screen. If there's a little but not a lot and not larger pieces of it, you may be able to replace the weak tensioners and be OK for a little while. If not, you're talking about a rebuild to get to those inside the motor.

This is just one potential cause, but it could be something metal just rattling like a heat shield that does it at that resonant frequency. An automotive stethescope might help you determine where you hear the noise from if you can recreate those temperature conditions on a lift and then bring the revs up to 3000 rpm while you try to listen to different parts of the motor.

Chris Ferrell

Hi Petza914, thanks for suggestion.

Yeah, oil always looks good. Had the sump out recently and all was well. More of a faint rattle that gets a bit louder as water temps rise. And only around 3k. No noise when the car is cold. Noise doesn't sound like it's timing chain slap. I do have the engine ears, tried that but still hard to pin point. Will prob give that another go sometime soon.

Petza914

When was the water pump last replaced? Maybe as the bearing heats up from the coolant it starts to squeak.

Chris Ferrell

Water pump is 4 years old at this point. But I think I'll check all the auxiliary bearings again, could be what your saying.

Added a vid of the sound too: , that's me holding it at around 3k RPM after it's been warmed up to temp. Rattle starts at about 10 seconds in.

Petza914

I definitely hear it, but haven't heard that sound on a 997 before and don't know what it is. It sounds almost like high pressure air escaping - for lack of a better term, like a "fart" sound (sorry). On your exhaust system is there any evidence of a leak at any joints - like round carbon spots - that's what would happen when condensation from inside the exhaust leaks out there and mixes with the carbon or maybe noise escaping through the AOS diaphram. But if it only does it at at that specific temperature and RPM and doesn't continue to do it either colder or hotter than that, it's very odd.

bgoetz

TheBruce

Yea that's not one of those noises only Porsche owners hear :-)

Personally I wouldn't drive it until its diagnosed. That doesn't sound like a rattle. Its sounds more like a wood chipper, but maybe its just more pronounced in the video.

Doesn't sounds like a bad timing chain tensioner. That would only be heard for a few seconds until oil pressure built up.

Have you inspected all the accessories, the accessory belt and the airbox? Ive heard stories of the oil fill tube and airbox getting chewed up by the belt and accessories.

Where is it coming from?

semicycler

Get one of those cheap mechanic stethoscopes from Harbor Freight or the local auto parts store and start probing around the engine. Start at the top end around the valve covers. Also check the tandem oil/vacuum pump on the lower rear right of the engine. You'll know pretty quickly if it's an engine noise or not.

JW911

I had a very similar issue with my 2005 997. It sounded almost identical. The only difference is that it was not readily replicated like that when the car was parked and revved. But it did follow your general description of when you are hearing it while driving. My dealer struggled to find the sound. They actually replaced a catalytic converter and the engine mounts (under warranty) which had no effect. They finally determined that the sound was coming from the oil pump. They replaced it under warranty and the sound was forever gone after that. I never experienced any problems with oil pressure, just that sound. I imagine the sound is driving you nuts. I would point them to the oil pump and cite my example if they are in disbelief. My dealer had never experienced the issue before. I am lucky they found it.

Chris Ferrell

Thanks all!

I've pulled of the belt and all the auxiliary and bearing feel good. And airbox, etc sits correctly. Traveling for the holidays but will dig in again once I'm back.

The first recording is from the left rear, just behind the back bumper. Def a lot more faint while in the car. And also more faint when listening from top of engine. So I think it's coming from lower down, but always hard to tell with these sounds.

@JW911 - thanks for that, I'll use my engine ears around the oil pump to see if I can hear it more pronounced there.

Another one (left side under headers):

And one from the top (Left side):

TheBruce

I sent that video to my buddy Wells at S-Car-Go. He said it was some sort of resonance, likely with the oil pump, and its not something to be concerned about. He said he's heard it on many Boxsters, 996s and 997s and they never replaced them at the dealership, and strangely never got complaints about it either.

I think thats should make you feel better...but personally I wouldn't sleep until I found that damn gremlin.

Chris Ferrell

@TheBruce thanks for reaching out to S-Car-Go! That's great, I'll focus the engine ear around the oil pump once I'm back under the car.

SonicJLee

Hello, I'm experiencing the same sound/symptom on my 2006 C2S, just more pronounced on the right (passenger) side of the car. I haven't found anything from a visual inspection. Were you able to resolve the issue? If so, how?

Thanks,
Joe

Petza914

Is it exactly at 3,000 or could it be slightly higher. I'm thinking maybe one of the variocam plus solenoids is behaving improperly which it think start moving at around 3,800 rpm. If it's slow, you might hear the noise then have it go away. If you accelerate slowly you can hear in the exhaust note when the solenoids move, as the tone changes. If this is also when the other noise starts, I might look into that.