Cayman Strange Noises -- The Saga Continues!
 

So, I thought my Cayman "strange drivetrain noises" drama was over (see this thread: Unpleasant Engine Noise in my Cayman S -- NOT a Blown Engine! , as well as a couple here on Pelican OT) : 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.

https://www.youtube.com/watch?v=UT333r2tV5Y&feature=youtu.be&app=desktop

Thanks, and I eagerly await your thoughts.

Although it is at the wrong end, I had a buddy loose his crankshaft pulley . We don't know if the bolt broke, or if it came loose , then broke, but the end result was his pulley falling off , with a stub of a crankshaft bolt stuck in there Worth a listen, and a quick check anyhow.

The very first time I heard the noise, my first thought was, "hmm, that sounds like a belt slapping around or a pulley out of whack." But I'm not sure why having the car in gear would affect the noise...

Very weird. It almost sounded like you were clicking a pen or something. No idea, but glad the other issue was nothing. Good luck on this one.

My first guess as I read through your description "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." My first thought was maybe a tiny exhaust leak or crack. Those sometimes sound like a high pitched tap and can go away when things get to full temp, but I'd also expect them to be more regular. It also wouldn't surprise me if you didn't hear them when the engine was revved.

Run it without the belt for 30 sec to rule it and pulleys out.

Sounds like exhaust leak or another plug loose? Does it change sound with cold engine vs hot?

The sound only recurs when the engine is warm and at idle. Cold = nothing. Hot, after a long drive = nothing. There seems to be no pattern to the sound itself -- sometimes it's a quiet tap, sometimes a louder one; sometimes it's a single tap, sometimes two in a row.

It's also curious that engaging the clutch and putting the car in gear seems to change its behavior.

Moreover, when you rev the engine a little bit at idle and in neutral -- say, if you rev it to 1500rpm and hold it there -- you can still hear an occasional "tap," but with the same randomness as before; totally independent of what the engine revs are doing.

That noise is weird. It sounds like something is loose and hitting something rotating intermittently.

I agree! The best analogy I can think of is "a pair of jeans in the clothes drier and once in awhile the zipper smacks against the drier's wall."

But here's the question: what would be loose and slapping something but not be affected by engine RPM, but WOULD (presumably) be affected by changing the clutch/gearbox relationships?

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

Have a mechanics stethoscope? That is what I would try to narrow down the location/component.

Lets review the oil change that " may " have started the noise you are hearing . What oil came out of the car ? What went in ? I am NOT suggesting this turn into an oil debate war . Maybe it's as simple as different brand/weight causing this ? Or maybe not .

Going out on a limb here...

Is there any chance it is a fastener or hose clamp either loose or not that may have gotten moved or otherwise placed in close proximity to some other vibrating part? I'm thinking like a heatshield or something... related only to the movement of the engine by the vibrations caused by the engine. Perhaps is comes and goes only when the engine is warm due to thermal expansion... when cold, it can't contact and when it is hot, it moves beyond being able to contact.

What is the condition of the engine and transaxle mounts? If they are worn or loose, that may explain how engaging/disengaging the clutch may be affecting it.

This may be completely off base but it may be worth looking at everything around the engine and not just the engine, itself.

To me, that noise is something free and being intermittently flung about in a confined space such as the crankcase. Is it louder on one side of the car than the other? If so, it could be in a head. If not, crankcase or bellhousing.

That noise could be as described above, something rattling around, but it also sounds like thermal expansion in sheet metal. Exhaust components often make ticking sounds as they change temperature. You most often hear it as an exhaust system is cooling down after shutting an engine off, but it can make noise while warming up, too.

Of course, complicating matters, this was an oil change that has a few factors. Up to this oil change, I had been using 0W-40 Mobil1 and the stock filter, but for more protection I changed the oil to Joe Gibbs' Driven D40 5W-40 AND switched to the LN Engineering spin-on filter adapter (with a strong magnet element to trap debris).

At first, since I heard the noise right after the oil change, I thought the oil change must have something to do with it. But then, I reasoned that I might be hearing it right after the oil change simply because I don't let the car idle in the echo-y garage all that often and the sound is difficult to hear when idling in the driveway or out in the world.

But then I came across this post on Rennlinst: https://rennlist.com/forums/987-981-718-forum/675830-engine-tapping-flapping-noise-only-at-idle.html

He also had a new noise develop after installing the LN Engineering filter, and proceeded to spend thousands of dollars tearing his engine apart trying to find it. Finally, after month$ spent trying to track it down, one day he sacrificed the quarter-gallon of oil in the filter housing and just put his stock filter back on... and the noise went away.

Of course, even though his sound seems to be different than mine, I tried this. I also put the stock filter assembly back on (with a new paper filter). Didn't work for me. But I still wonder if the switch from Mobil1 0W-40 to Driven 5W-40 might be affecting something differently (especially if the culprit ends up being a lifter or a part that is involved with oil delivery)?

The noise is a little like the ticking of exhaust after the car is turned off, but a bit louder and more insistent. It also seems to be loudest near where the engine and gearbox meet... although I suppose that's near where the exhaust is as well. Doesn't explain why the noise would be affected by clutch/gear changes, but I'm not ruling your idea out, either.

Pelican definitely gets the award for "most helpful forum" this time around. The only response I got on Rennlist suggested it might be "Neutral Rollover" in the transmission, which is "benign but annoying." I'm not really sure what any of that means. I listened to a couple of YouTube videos of "neutral rollover," and it sounded nothing like my noise.

I'll throw in my 2 cents of usually wrong input.


Have you been under the car yet looking for stuff?

To me, It sounds like a heat shield or something going through thermal expansion. I am unfamiliar with the cayman underbelly, and tried looking up google pics of the area, but couldn't find much.

Is there any chance there is some thermal shielding in the area of the slave cylinder for the throwout bearing, that is being compressed/ affected with clutch actuation, ever so slightly. The piece of metal is clicking as it expands, the act of engaging the clutch is moving something ever so slightly to brace the metal so it can't cause a racket?

http://forums.pelicanparts.com/uploa...1502456929.jpg

The closest pic I could find was this- and I didn't draw that arrow, but the shielding above it is the type of shielding I could envision making that noise, especially if it isn't secured to the car right. It would be on the light weight side of noise casusers- compared to the exhaust. I don't know if that is what yours looks like, but I would be under the car examining the area, tightening all bolts around slave cylinder, making sure no shielding is contacting anything/ and flexing it to make sure it isn't loos either, perhaps even bending it a little to try to see if by changing the set of the heat shields affects the noise.

If it was my car, my head would be spinning with the pia possibilities that one of the clutch plates bolts was slightly loose or something like the throwout bearing, but my guy instinct this is an easy fix.

edit :)
Never mind- now that I think about it the exhaust fits better- but I'd still check that area esp. closer to the engine.

Good luck
ron

That's really weird. Have you pulled the access panel and checked the belt? I wonder if your tensioner is getting weak and the belt is intermittently slapping?