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Discussion Starter · #1 ·
So, I thought my Cayman "strange drivetrain noises" drama was over (see this thread: http://www.planet-9.com/987-cayman-...ngine-noise-my-cayman-s-not-blown-engine.html ) : a few weeks ago, I noticed an intermittent "tapping" or "flapping" sound at idle in my garage right after an oil change. After a day or so, this intermittent noise seemed to turn into a more regular "tapping" noise. Apparently, the more regular, rhythmic noise was a different issue entirely.

Because of all the internet stories about the m96 and m97 engines, I feared the worst. I sent an oil sample to Blackstone and had it towed to my local speciality shop, where they scoped the engine, checked the oil filter and sump for debris, and found nothing wrong. Moreover, the oil analysis came back from Blackstone as being perfectly within specifications; in other words, my car had a clean bill of health. During the scoping of the cylinders, the mechanic noticed that a spark plug was loose; sure enough, tightening down the spark plug caused the rhythmic tapping to go away -- it was just compression escaping from the spark plug hole all along.

Well, it turns out that that didn't solve the initial noise that I heard awhile back. This noise is hard to describe, but I would call it a very intermittent and irregular tapping noise that is totally independent of engine rpms; you'll hear a tap, and then a few seconds would go by and you'll hear two taps in a row. And then there will be a long, quiet stretch, and then another couple taps, etc. When you rev the engine, you no longer hear the tapping; if the car is still making the noise, it is separate from the noise of the engine and can't be heard over the sound of the revving engine.

Moreover, I only hear the noise when the car is WARM but not HOT -- you can start to hear it 30-45 sec after starting the car when it's cold, but if I go out for a long drive, it doesn't make the sound when I pull the car into the garage and let it idle there.

It doesn't sound good, but I'm comforted by the fact that it seems to have nothing to do with the rotation of the engine internals. Part of me wonders if it has something to do with a pulley -- or maybe the water pump?

I also notice that if I push in the clutch, the noise lessens but doesn't go away completely. Then, if I put the car in gear and let it roll in 1st or Reverse, the noise stops completely. Let out the clutch, it comes back. Push the clutch down again and it's gone. So maybe it's a throw-out bearing? Or gear chatter? Or something to do with the clutch disk or flywheel?

Anyhow, if you guys could take a listen and let me know what you think, I would be appreciative. You'll have to listen carefully to the video: you first hear the tap right before 7 seconds, but then it gets more regular, with a couple quick taps at 8-9 seconds. There quiet stretches in between when you won't hear anything other than an otherwise fine-sounding flat six. Near the end of the video, I move the camera closer to where the gearbox meets the engine, and you can hear the tapping much more clearly then.


Thanks, and I eagerly await your thoughts.
 

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Discussion Starter · #2 ·
I've listened to about two dozen video clips of 987s, 986s, 997s, and 996s on YouTube in order to find one that sounds like my car. The only one that seems to have the same issue is this guy, who posted about the same kind of intermittent noise in his Boxster 987 back in 2014.

In his case, the Porsche mechanics just "shrugged" and said it was normal lifter noise (???)

He hasn't posted since this original thread, so either the issue was resolved or he perished in a 987-shaped fireball shortly thereafter.

His first video is the one that sounds like my car's intermittent tapping:

https://rennlist.com/forums/987-981-718-forum/761436-987-newbie-questions-engine-rattle.html
 

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Sounds pretty normal to me. Is this your first Porsche? You seem to be obsessing about it and letting it drive you crazy. These engines have a tendency to be a llittle noisier than your typical American car, mostly because you're practically sitting on the engine. I suggest you start driving it and enjoying it instead of worrying about every different kind of noise you think you hear. :cheers:
 

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Discussion Starter · #4 ·
Sounds pretty normal to me. Is this your first Porsche? You seem to be obsessing about it and letting it drive you crazy. These engines have a tendency to be a llittle noisier than your typical American car, mostly because you're practically sitting on the engine. I suggest you start driving it and enjoying it instead of worrying about every different kind of noise you think you hear. :cheers:
Fourth Porsche. First flat-six.

That irregular tapping sounded normal to you? I agree that the engine rotations sound fine -- none of the ticking or chugging that suggests "lifter problems" (usually a misdiagnosed scoring issue) -- but that tapping seems strange.
 

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Hard to tell from the video, but it does not sound like anything from deep within the bowels. Unless the video is somehow exaggerating the issue, it would drive me nuts. Don't see how that somewhat random tapping could be considered normal. Sounds like something is occasionally hitting something else - I just can't guess what.
 

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Definitely external to the engine. Maybe a heat shield or something. I'd put it up on stands, crawl under there, remove the covers if necessary, and start tapping on things with a rubber mallet. I bet you can find it.
 

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Discussion Starter · #7 ·
UPDATE.

First, thanks to all who responded so far. I'm trying to narrow down possibilities, and so all of your ideas are valuable.

In order to narrow down what might be causing the noise, I ran the car to make sure that it was making the noise, and then took off the drive belt to have a listen, and then replaced the drive belt to listen again.

Start #1 -- Belts On: There's the noise, clear as day.

Start #2 -- Belts Off: I heard literally one "clack" that was definitely the noise I was listening for, but that was it. Other than that, the car didn't seem to be making the noise in question. Take a listen:

https://www.youtube.com/watch?v=6gZ8MwrBFA8

Start #3 -- Belts On: The noise is back, just as in Start #1. Take a listen:

https://www.youtube.com/watch?v=YWKjcccw8JA

The removal of the belts DEFINITELY has an effect on the nature of the noise. Although I have heard single, solitary "clacks" with the belts off, they are very sporatic and not nearly as frequent as when the belt is on, to a noticeable degree. The car definitely runs smoother with the belts on (obviously, since the lack of an alternator with the belts off means that the car literally has less power), so maybe the rhythm of the engine might be a factor here? Thoughts?

Also: I threw a CEL when I ran the car with the belt off. Is that normal? In other words, was it caused by running the car without a belt, or might it have been caused by whatever is causing the noise?
 

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For some strange reason, none of your videos audio play on my PC. Strange.
But I have a suggestion. Try turning off your A/C and see if you hear the clicks.
 

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Discussion Starter · #9 ·
YOU'RE A GENIUS. I had my A/C off the whole time this was going on (it's only in the mid-70s here in CT today).

BREAKTHROUGH!!!

I had the engine running with the belts on, and it was making the noise.

I turned on the air conditioning (which was somewhat noisy with the belt cover removed).

The noise disappeared.

I turned the air conditioning off again.

The noise came back.

I feel suddenly at ease that my engine isn't going to explode... but what does this mean? What's going on? Why would turning on the AC turn OFF the noise?
 

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YOU'RE A GENIUS. I had my A/C off the whole time this was going on (it's only in the mid-70s here in CT today).

BREAKTHROUGH!!!

I had the engine running with the belts on, and it was making the noise.

I turned on the air conditioning (which was somewhat noisy with the belt cover removed).

The noise disappeared.

I turned the air conditioning off again.

The noise came back.

I feel suddenly at ease that my engine isn't going to explode... but what does this mean? What's going on? Why would turning on the AC turn OFF the noise?
As you know, the AC compressor's pulley is always spinning via the belt. But there's an internal clutch or something that cycles on/off electrically from signals from the control unit. So it might be something in the compressor. Or wiring causing the compressor to cycle.

Another thought is that with some cars you never really have the AC completely off. So maybe it is supposed to cycle even when off.
 

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As you know, the AC compressor's pulley is always spinning via the belt. But there's an internal clutch or something that cycles on/off electrically from signals from the control unit. So it might be something in the compressor. Or wiring causing the compressor to cycle.

Another thought is that with some cars you never really have the AC completely off. So maybe it is supposed to cycle even when off.
yeah good idea - since you've got the front engine cover off to remove the belt, you could watch the AC pulley and see if the clutch pulls in when the noise happens.
 

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Discussion Starter · #13 ·
The AC compressor on our cars is clutchless variable compression. You may just be hearing the hydraulically actuated piston swash plate adjusting compression and returning to low.
I'm not really sure I'm following, but I'm interested in what you're saying. So, the failing part might not be a A/C CLUTCH necessarily, but it is clearly part of the A/C system, right? I mean, I heard that very strange sound and the sound went away when the A/C was turned on.

I will say that shutting off the A/C with the belt exposed gave a surprisingly loud "click" -- louder than I was expecting.
 

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So it appears to be switching noise when the AC compressor kicks in/out. Per sjfehr it is not a traditional magnetic clutch, but a hydraulically activated piston. In any case I guess yours is louder than normal and might be a sign of impending failure, or maybe it will live on for years and now that you know what it is, it might not be as annoying.
 

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Most car ac systems are on/off controlled by a 12v magnetic clutch. Ours are not, our compressors are always spinning, and the compression is controlled by a swash plate (like a helicopter) that changes the compression level of a series of pistons. When the ac is off, it's flat. When ac is full blast on a hot day, it's at full displacement/max compression. The computer is constantly adjusting it as rpm changes and disables it completely when you're wot.

A 'click' is probably not the sound of impending doom. So long as it keeps blowing cold air, I wouldn't worry about it. It's a Denso 7SEU if you want to google for more info.
 

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My 06 Cayman S makes the EXACT same noise. I’m glad this thread was revived as it sort of puts my mind at some ease. I thought I had a sticky lifter or bore scoring but like the OP, my car’s intermittent ticking or clacking noise mostly goes away when the a/c is on. I haven’t tried idling with the belt off but that will be next. My car only does it when up to temp and it goes away completely by revving above 1000 rpm. I will be putting in new spark plugs soon so we’ll see if any are loose. I’m wondering if it’s possibly a belt tensioner?

I hope someone figures this out. It’s more than slightly embarrassing sitting at a stoplight and having this clacking sound hammering away.
 
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