paradigm79

First post here, long time lurker of this and just about every other Porsche forum. I've searched and read just about every thread I can find with similar symptoms but I'm still a bit stumped and hoped one of the many engine experts out there could help with a diagnostic path to take. Sorry for such a long post right off the bat, but hopefully some of this info may be helpful to others regardless of the outcome.

For starters I have a 07 Cayman S, 6spd, 46K miles and have heard this intermittent tapping noise off and on only at idle for some time now. It had to be dead quiet and sometimes hard to hear if outside the car, unless inside the garage or similar. I purchased the car back in the spring but since the weather has turned cold it doesn't appear to idle dead smooth and to me almost seems to stumble or "shiver," for lack of a better term, occasionally while idling. All this is only at idle (it either doesn't exist or I can't hear it even at the elevated cold idle RPM) and otherwise it sounds, feels and pulls fine as far as I can tell.

Here are some sound clips. I know based on the sound it sounds like a lot of IMS (suspected or actual) clips posted, but it really seems like its coming from the other end of the motor...read on.

Inside the car:
Under car, left side, front of engine:
Under car, right side front of engine:
Recently it seemed to be less intermittent so I took it by the dealership to get their opinion. They were a bit stumped too as they couldn't tell where it was coming from... but agreed its not normal. They claimed to have hooked it up to the PIWIS and the cam deviations "looked fine." While there we also cut open the oil filter (I'm using the LN spin on adapter) and it was 100% spotless. So, based on noise alone their guess was a broken valve spring or a stretched timing chain flapping around. In the ~5K miles I've had it, I've never had a CEL and they claim they found no stored codes. They also assured me the idle behavior was fine, but you can hear it hunting slightly in the sound clip recorded inside the car. Since they quoted at least $1K to tear into it and attempt to confirm their diagnosis (and then more to fix it of course) I opted to bring it home as I would instead prefer to invest my time and buying tools if needed.

I started by changing the oil and inspecting the magnetic drain plug, no signs of ferrous debris found on the magnet. Sent off the oil for a UOA and it came back clean, see attachment. I removed the bottom plastic panel, top engine cover, and firewall access panel behind the seats and began probing everywhere with a mechanic's stethoscope. I don't have much experience doing this with a stethoscope, and none on these engines so I may have missed a good spot to check. Long story short I couldn't pin point the sound, but I could best hear it when placing the probe on the lower idler pulley center bolt (the one just to the left of the tensioner pulley), yet not as well if I placed it on the engine case just behind that idler. While you can't see it, I also noticed if you place your finger on the tensioner center bolt or tensioner arm you could feel it vibrate quite a bit. (Is this normal?) I was half way hoping it was the water pump, but when I placed the probe on the water pump housing it seemed pretty quiet.

In any case, I removed the belt and there was no obvious sign of damage or wear. I fired up the engine without the belt, and couldn't hear the noise but it was still cold and I wasn't sure how long it was safe to run without any coolant circulating so I shut it down long before it started to warm up. Interestingly, the only accessory pulley that didn't seem to have any free play or make noise was the water pump. If nothing else, can someone comment whether or not this is "normal" play? Either way, all the accessory pulleys were quiet while turning when the belt was on.

So, I replaced both idler pulleys with new ones and tried again. No dice, sound came back at warm idle. (And by warm, I just mean when the RPM drops, not that the oil temp/pressure has reached steady state warm.) I did not install a new tensioner pulley as the bearings on that one felt ok compared to a new one.

I have read one post in particular that made me think it may be a failing or failed variocam actuator, so I have a durametric cable on order in hopes of testing that.

I have all kinds of questions running through my head, in particular does the evidence so far actually eliminate the IMS? Wouldn't a broken valve spring throw a CEL and even if not, cause symptoms at higher engine loads...not to mention probably crashing the valve into the piston at higher engine speeds when it can't get out of the way fast enough?

And FWIW, It doesn't consume or drip any oil. Averages 21-22 MPG around town, 27-28 MPG interstate, and indicates 14-15 psi oil pressure at fully warm idle based on a high quality OP gauge I installed in the spare port in the head on the 4-6 bank.

I'll stop here in hopes of some advice or plan of attack either through inspection or the durametric in route.

equ

I had an intermittent ching-ching (or tick-tick?) at hot idle with my 06 cayman S. It started at around 14k miles and still had it at 33k miles when I traded it in. It didn't do it every day, but it did it most days and having the engine fully hot made the sound come out. Went to dealer twice for it, over two years. They didn't hear it the first time. Second time, they claimed to check some injectors etc and said all was well. When I asked about lifters, they said that the complaint was noted so would be covered if it got worse after warranty end. I did an oil analysis as well, showed a bit of lead in the report. Could be bearing or remnants of fuel additive said the report (which I also use). It didn't make the sound, already faint, the day I took it to an indie. Another indie, not porsche specific, but someone who does oil changes for me and generally an experienced MB guy thought it was coming from the head, likely lifters. The porsche dealer's driver, the lowest person on the technical totem pole, heard it and thought it might be a pulley. It sounded like your last video's pulley sound superposed onto the idle at 2-a second beat.

Good luck.

Macster

No CEL. No real abnormal engine behavior. UOA came back clean. Cam timing appears ok. Nothing scary in the oil filter.

Have you had your head examined?

Sorry. Cheap shot.

Seriously, the noise doesn't sound that bad. But the dealer did say that it didn't sound normal. However, that may have been said to push you towards spending some money, I'm sorry to say.

Remember these are reciprocating engines. They are full of hardware that is moving back and forth, things rotating like crazy, have miles (it seems) of chain drives, 24 valves each with a lifter and each being opened by a cam lobe pushing down on the lifter top. Injectors are opening/closing every cylinder's intake stroke and a 50K volt spark is being generated every power stroke.

Hot exhaust gases are being shoved from the cylinders to the exhaust manifolds and there to the outside.

If the engine wasn't noisy I'd be surprised.

Really the location of the noise needs to be id'd. Getting the car to the point it makes the noise and getting the car in the air safely and listening at various locations with a mechanic's stethescope until you (and someone else) agree the noise is coming from as specific a location as possible is needed.

Once you have id'd where the noise is coming from then what is causing the noise is maybe easier to guess.

Cold weather makes a car noisier. And our imagination can really make the thing sound like it is at death's door.

Oh, if the car's a manual does the noise change any if you depress the clutch pedal and hold it down? Sometimes a manual equipped car will develop a clutch rattle or even an input shaft rattle that sounds like it is tied/related to engine speed but can vary just enough to drive one crazy.

There could be an exhaust leak too. Generally they are noiser at cold idle then quiet down as things heat up (as the crack in the exhaust closes from heat expansion) but not always. Depends upon where the crack is located.

Or the noise could be a loose heat shield, some exhaust hanger is loose or cracked or a hose flopping about. Really you need to pinpoint where the noise is coming from to have a better chance of id'ing its cause.

The CEL is off, so the cylinders are performing equally well. The engine runs ok otherwise. Oil consumption is ok. Fuel consumption is ok A bit of 'shiver' or stumble at idle from cold can be normal as the weather gets colder.

I am sorry to say I do not recall what kind of play the belt idler roller bearings had on my Boxster nor the tensioner roller. I do recall that when I suspected a water pump the pump puolley had a bit of play, not much. It was only noticeable because the other accessory drive pulleys were so free of play. Also, the belt had a sharp (inside) edge from the belt rubbing on the water pump pulley because of the play the belt was not tracking properly.

If you want, you may consider switching to a different oil. Stay with an approved oil but say instead of running 0w-40 switch to a 5w-40 or even a 5w-50 oil. (Mobil offers an approved 5w-50 and I run it in both my cars in the summer. I might add I couldn't tell you which oil is in either engine based on noise. As best I can tell the engines emit about the same level/types of noise no matter the oil. I do believe that as the oil gains miles -- I change the oil every 5K miles -- the engines get a bit noisier and I've changed the oil often enough that I am sure that upon refilling the engine with fresh oil and even warmed up to operating temp the fresh oil makes the engine quieter. Not oodles but some, enough to notice.)

However, if you live/drive in a place with temps drop to -25C Porsche recommends you stay with 0w-40 oil, but if you live in milder climes a slightly heavier oil may just quiet the engine.

Sincerely,

Macster.

paradigm79

Thanks for your reply and all very good points. It is surprising that reciprocating engines don't make more noise than they do, but that's just it...a properly functioning and tuned engine does purr (and that does include the continuous nature of valvetrain clatter, etc.) Right or wrong Jake Raby and others have made the point many times these motors are no different and are "quiet" when working properly. The noise I hear may very well be benign, which I'm ok with, but I won't know that until I find it.

I have had the car up in the air for a while now with lots of panels removed so I could poke and prod all over with my stethoscope. As I mentioned before, I can hear it best from the lower idler center bolt, but I know sound can transmit in funny ways so its hard to tell where it may really be emanating from.

I have held the clutch in and it does not change the sound. I have had that sort of rattle in the past, but no luck this time. I have also fixed a heat shield rattle on this car already, which in my case sounded more like a buzzing noise around 3k RPM. I am pretty certain this noise is coming from the engine/drivetrain.

With this last oil change I switched to 5W-40 and so far nothing has changed, however I have only idled it on the stands since changing it and have not taken it out for a thrashing. Maybe I should...or maybe that will blow it up

So, assuming my head is not what's broken, can you help in a diagnostic sequence? I will tear into it if I need to, but I would like to eliminate everything on the outside before going inside. Durametric should be here today if anyone has some pointers.

Thanks.

Macster

Well, 'quiet' is a relative term. For instance, these engines have camshaft chain drives and are going to be noisier -- all other things being equal -- than engines with rubber (timing) belt drive to the cams.

Also, the engine is located at a place that is more likely to have the driver hearing engine noises. The engine compartment is a bit more open than say a front engine'd car's engine compartment.

With that out of the way, you've located the noise at the front of the engine around/near the lower idler roller. I haven't taken the time to re-read your posts but have you replaced this idler roller and its bearing?

Or if you do not want to throw money at a suspected noisier idler roller bearing, you can swap the suspected noisy roller for a quieter one and see if the noise follows the suspected roller. Try to swap rollers that are as far apart as possible.

For a diagnostics sequence, if the noise is present at cold or warm engine start you can remove the serpentine belt -- carefully note its routing and direction of rotation so you can reinstall it the same as it was -- and start the engine. A cold or mildly warm engine can idle a bit without any risk. 'course you want to run the engine only as long as it takes you to verify the noise is still present or is absent.

If the noise is not present, an idler may be the source of the noise, though it may not be the one that you think is noisy, or the tensioner or even a water pump (or some other accessory drive, but I have heard a water pump make noise).

If the noise comes from an accessory drive the one with some (any) play at its pulley/shaft is the suspected bad one. You have a couple of accessory drives so feel/test them all going around several times. The one with the play, if there is one, will become evident.

If the noise is still present then the idlers/tensioner/accessory drives are not the source of the noise. Which puts it inside the engine.

If the noise is clearly coming from inside the engine, I am not qualified to advise you beyond this point.

The engine may be healthy just a bit noisier than other engines. Noises are hard enough to classify even when one is at the engine.

Or if the engine is truly noiser than normal, than it should be, the noise might due to some known problem. I vaguely recall in some late model Caymans and maybe Boxsters too the oil pump or oil pressure relief valve could make noise.

Sorry about that having your head examined crack. Obviously it is *my* head needs to be examined.

Sincerely,

Macster.

paradigm79

While I can still hear the noise clearly through the lower idler bolt (to answer your question, I did replace both the idlers to no effect and I've also played with the serpentine belt on vs off, etc...didn't fix it.),

However, I have now found an additional place I can hear it well. If I probe around the engine case right around the oil filter I can hear it very well. I know this is at the opposite side of the engine but noise travels in funny ways sometimes. The quality of the noise is quite a tapping/snapping/whacking noise. I have heard (and replaced) spun crank/big end bearings before, this does not have that heavy knock quality to it. The sound goes away completely as soon as you tip the throttle, I mean just even breathe on it, and does not return until it settles back into a normal idle. As much as I try, so far I can not hear it anywhere around the valve train area. Durametric also showed the cam deviation values to be rock steady, and the actual values less than 1 degree from nominal at idle. I think this in conjunction with the UOA rules out IMS bearing completely.

Based on the new location of the noise, and as you suggested, you may be right about the oil PRV or maybe the oil filter bypass valve. Although I am using the LN spin-on adapter and wonder if this may be playing a role. The only other thing that comes to mind is one of the chains smacking around. Even though the two examples given are tiptronic cars (and mine is 6 spd) Item # 8 in the first post here could be it as well based on the symptoms.

No worries on the head jokes.

No HTwo O

Correct, there was a TSB (ENU #1726) issued by Porsche in February 2006 for the replacement of the control piston in the oil pump (997.107.125.01 and 996.107.123.50 for the seal).

Paradigm, is all of your maintenance up to date, for both mileage and time? Spark plugs and coil packs are A-OK 100%?

No HTwo O

Rob, quick note, you state that you are using M1 5W40 but Blackstone thinks your last oil change was 0W40. Have them make this correction and re-run your report, so they are using the correct database for the viscosity ranges in the bottom portion of your UOA. Blackstone has made this error with my recent report, too (they used 15W50 date and my oil was actually 20W50).

paradigm79

Thanks for the heads up, but the report is correct. It may have been confusing how I wrote it. I drained the M1 0W-40 for that last UOA and then replaced it with Castrol 5W-40.

Macster

If a camchain smacking around is the source of the noise I think you'd see signs of a failed chain tensioner: bits of some kind of o-ring/seal material; or a failed rail/guide: bits of hard composite plastic of either a dark brown or caramel color depending upon which camchain and rail/guide; in the filter elemet and filter housing oil.

Additionally I do not think the cam timing deviation values would be that rock solid.

As for the LN filter I am totally in the dark about its design/construction. About all I can offer is if it has some kind of pressure relief/check valve in it, this might account for the noise.

If you suspect the LN filter, how hard is it to go back to the stock filter, at least temporarily?

Sincerely,

Macster.

No HTwo O

Or give Charles N. a call or e-mail. I have always found him to be very-very helpful and responsive.

paradigm79

So I haven't posted in a while but I have been working on it. I dropped the transmission and the DMF was way out of spec, almost 3 times the free play it is supposed to have so I ordered a new one. I also found tons of black magnetic dust all over the bottom of the bell housing and crank case, reported by others as indicative of a failing DMF. The clutch disc still had plenty of material left, measuring about 1.8mm from the face down to the flared rivet heads. I have read that brand new is about 2mm and the service limit is 0.3mm.

I installed a new DMF, TOB, TOB guide tube and seal, lightly lubed up the various parts and put it all back in. The bad news is the noise came back. As before, it was quiet at the faster cold idle and remained quiet once it warmed and slowly settled to a normal idle speed. So for a few minutes I was thinking all was well, but I learned before that once warm, the real test was revving it up and letting it resettle to idle. The resettle is what would bring out the noise and the slight hunting rpm at idle. This time after the new DMF was installed was no different. At this point I'm not sure what to do next other than just drive it and maybe find a few indy shops to take it by and let them listen. At least the DMF was pretty shot so the work wasn't totally a waste.

What could remain quiet if it settles to idle slowly, but become noisy if it drops to idle quickly? Ideas welcome.

Macster

Have you considered that control piston of the oil pump TSB that _No HTWO O_ referenced in an earlier post?

"TSB (ENU #1726) issued by Porsche in February 2006 for the replacement of the control piston in the oil pump (997.107.125.01 and 996.107.123.50 for the seal)."

Sincerely,

Macster.

paradigm79

Yeah all my maintenance is up to date. As part of all this I removed all the spark plugs and all looked fine, but I replaced them anyways as its about time at 47,000 miles. The coil packs looked ok, no cracks, discoloration, etc, but I did not test them specifically and I reinstalled them. While I had the spark plugs out, I borrowed a bore scope and looked in each cylinder, no scoring that I could see and the piston tops looked ok. Cylinder walls on #6 and 5 showed a few light gray lines on the thrust side (upper) but no real scratches to speak of. While this is less than ideal, apparently its fairly common on the larger displacement M96/97 engines according to Hartech.

I did briefly, but I ruled it out because I read the information below and the symptoms didn't fit my case, nor do the built dates listed (is the info below correct?). I have a M97.21 MY 2007, but I guess there is a chance its still faulty.

"Vehicles/engines affected: 2005 up to 2006 Boxster (987)/Boxster S (987) with M96 engine.

A screeching noise can be heard from the engine at around 2,000 rpm during the engine warm-up phase. In many cases, the noise is an indication that the engine or oil pump has been changed. The noise is caused by the control piston in the oil pump.

Note: In the event of a complaint, a modified control piston must be installed in the oil pump cover.


Date of Introduction:

Engines manufactured since Dec. 5, 2005 as of *engine numbers:

M96.25 61 6 04763
M96.26 62 6 03668"

Marvin the alien

Hi all,
First post but I might have an idea for you. I actually think I have a similar issue on my 997 and have been trying to find somebody with similar symptoms.
The noise doesn't appear immediately, perhaps after 30 seconds or so of running. Tends to go away after 20 or more minutes of running and as you say idle feels a little off but no stalling...
My prime suspect is the purge valve, located on the inlet manifold I believe coming from the fuel tank evap system.
Hope this helps.
Marvin