Type_LT

I took a quick video from the rear of my 05' Boxster 2.7L with 39k miles. You can take a look at the video here (select 480p for better sound): http://www.youtube.com/watch?v=rL9_PsYkvow.

The sound has been coming going for the past 6 months. Naturally my first thought is a IMS bearing given all the panic (warranted) around that issue. It could also be the clutch throwout bearing since there seems to be a slight dependance on clutch pedal position. The noise is intermittent, sometimes after I stop the car it doesn't make a peep. Of course last time I took it in to let them diagnose a suspension issue, it was quiet.

Despite the Boxster being such fun to drive, I miss the mechanicals of my 944 Turbo. I never worried about that engine grenade-ing under normal use...

Macster

If the IMS bearing accounted for the noise you'd know it by now.

That the clutch pedal position plays a role of course brings to mind the possibility the clutch friction disc is rattling on the input shaft splines of the transmsision. Both my 02 Boxster (with 231K miles) does this and so does my 03 Turbo (33K miles). Both cars have to be quite warm, fully up to operating temperature, this includes the drive train. The noise is not present all the time even then. And depressing the clutch pedal *always* makes the noise go away and almost all of the time it stays away when I release the clutch pedal until the next time I drive the car.

If not the clutch friction disc then my next thought is the dual mass flywheel. How does the car move off from a standstill? If the clutch take up smooth? Any noises, clunks? What about shifting up or down? Nothing hot and heavy just normal shifting while driving normally.

If you tell me there is no untoward behavior moving the car from a standstill or while shifting then....

I do not know the history of the car. What was last done? Spark plugs? A loose or cracked plug can account for that sound, ignoring that it changes when you depress or release the clutch pedal.

One of the best things you can do is get the noise to appear and take it to a local dealer and have the car lifted in the air with the engine idling and the noise still present and let the technician pinpoint as best as can be done -- and it can be quite accurately pinpointed -- the location/source of the noise.

Once you know the location then this narrows down considerably the possible causes and helps make the next steps towards identifying the possible cause of the noise clearer.

Sincerely,

Macster.

Type_LT

Macster,

Thanks for the excellent reply (they always are!). I'll bet it's the friction disc rattling on the input splines since the clutch operates smoothly without any noises from a standing start.

The car has been serviced regularly at the dealership, no plugs yet, however I'll do them at my 40k service. The tech that works on the car has been there 30+ years and recently took a look at the car when I had a rubber suspension part go bad. At that time the noise wasn't clearly pronounced and we couldn't recreate it.

Thanks again for the reply.

Macster

You're welcome.

Your job is to without beating on the car learn how to cause the noise to appear and how to keep the noise present in order you can let an experienced tech hear the noise and have a chance to pinpoint its location.

Of course this assumes no other symptoms appear while you are doing this. If the noise gets worse, changes in any way, the engine starts running rough, anything, then shut off the engine as soon as it is safe to do so and arrange to have the car flat bedded to a dealer for attention.

I read in another post the car has 1 year remaining on its warranty. It is to your advantage to get this resolved as soon as possible.

Why? Well, to allow you to enjoy the car without worry for one.

Another is that if the problem is addressed under the car's existing warranty the warranty on the parts/labor of the repair only applies as long as the existing warranty is in effect. As soon as it expires, so does the warranty on the parts/labor of the repair.

So you want whatever's wrong id'd and fixed and the sooner the better so you can have some time to drive the car and ensure the problem is fixed once and for all.

BTW, it could still be a plug -- long shot to be sure. Even if they haven't been touched one could loosen or even crack. Another possibility is a crack or split in an exhaust manifold. These can emit a loud noise when cold and then quiet down as the exhaust gets hot or vice versa depending upon where the crack/split is located.

Just mentioning the above to be thorough. However, the clutch pedal affecting the noise I think puts the source of the noise at the clutch.

BTW, a co-worker who's got some movie making experience tells me the best clips/audio comes from having the camera mounted on a tri-pod. The tri-pod can be moved from say the rear of the car to each side in turn and located the same distance away from the car and at the same relative position.

Wherever the tri-pod is placed the placement wants to be symetrical. Center rear. Offset to either side of center by the same distance or angle and always the same distance from the car.

Also, if the gas pedal is used to increase the engine speed or the clutch pedal is operated etc. this wants to be done the same at each camera position.

And so on.

The audio portion of the clip you provided was pretty good though so don't be offended.

Sincerely,

Macster.

Type_LT

Macster,

It shouldn't be too hard to re-create, mostly just making sure it's warm. I have a hunch going in reverse up the hill into my garage has the effect of bringing out that sound.

I will take the advice to get it fixed asap, no need to prolong the process.

Next time around I'll grab my tripod and raise the camera off the ground. It was a bit dangerous to put the camera on the ground at that time anyways since the car was wet. Water and electronics sometimes have trouble mixing

insite

i think you need to drain the oil & look for metallic pieces. that noise doesn't sound like a clutch or throwout bearing. sounds like a rod bearing.

Type_LT

insite,

I'm going to have the oil changed soon and will take a sample before I do that to check for metallic chunks on the magnet.

Given that the noise decreases in intensity when the clutch pedal is depressed, I'm going to guess that it isn't a rod bearing. I do however have a noticeable vibration at 1200-1300 rpm when the engine held at that rpm with the car stopped and in neutral. I'd love to see the over-rev/redline data for my car to see if the PO was pounding it off the rev limiter for the first 32k miles. You'd think if that was the case they wouldn't certify the car, but who knows...

nosnow

I agree in that it doesn't sound like a rod knock, I think it is trans related. If lucky just a throwout bearing, you may want to drain the tranny fluid to see what it looks like as it may be a bearing in the trans.

Macster

There is a slim possibility the noise while affected by depressing/releasing the clutch pedal is not clutch/transmission related but engine related.

This is possible if the pads that limit the crank's linear movement are worn or worse. The noise is the crank moving back and forth and when you depress the clutch pedal and some pressure is added or released and this of course affects the crank's movement and the noise this movement causes.

Very slim possibility to be sure and I'm not 100% convinced my understanding of this possibility is even correct.

I'll see if I can do some more research.

I have no experience with Porsche engines but in other engines one main bearing has a thrust face that matches/mates with a machined face on a crank main bearing shoulder and these two surfaces provide whatever thrust control the crank requires to keep it located. The thrust bearing is well lubricated.

Now I have pics of a the insides of a Carrera engine that show not the thrust bearing face but the pads that serve this same purpose.

As with the thrust bearing, these pads just don't fail/wear out (something else fails long before these do).

If the transmission is removed I believe the mechanic can check the amount of end play the crankshaft has. It should be very little. Generally on the order a a few thousandths of an inch. Of course the mechanic should have references that give a call out of the allowable amount of movement.

Sincerely,

Macster.

Type_LT

Thanks nosnow (lucky guy to have no snow!) and Macster.

I would hope there is no issue with the crank but who knows, thanks for the response on that.

I grab some porsche spec tranny fluid and drain it this weekend when I do the engine oil. Speaking of engine oil, should I be sending the car to the dealer to perform the oil change so it's on the record? I don't enjoy being over-charged. However, in the long run the record may be more valuable if the engine grenades. Heck, if the previous owner followed the 15k mile oil change interval that could be half the problem right there (what are you thinking Porsche?). At least a Porsche has a good 7 liters of oil to last that 15k miles. In an Audi a4 the capacity is much smaller (4.2qt w/filter) and the dealership always recommends a 10k change interval. No wonder so many people had issues with gummed up 1.8t engines... </end rant>

As far as the tranny fluid goes I'll swap that out myself, wouldn't hurt at 40k miles anyways. I know the rear differential oil in the Audi looked like mud after 70k miles so 40k shouldn't be too soon.

nosnow

If the drivetrain is still under warranty I'd fork over the $$$ to have the dealer do both. Obviously something is wrong and it probably won't be cheap to fix. You don't want Porsche to say it was caused by a non-dealer service and therfore not covered.

If the car is out of warranty do it yourself.

Macster

I second what Paul said and I said something similar above:

"I read in another post the car has 1 year remaining on its warranty. It is to your advantage to get this resolved as soon as possible."

You can change the engine oil/filter yourself. When did this I'd tear off the oil filter box lid and write the date and mileage down and toss the lid in the car file with other paper work.

But there is more than just the oil/filter servicing required to keep all of the warranties on the vehicle intact. You need to read the warranty booklet that came with the car.

As for the noise, ixnay on changing the tranny fluid. Why are you bothering to diagnose this yourself. Even if you, I or someone guesses right the noise will not suddenly go away.

The best thing you can do is learn how to recreate the noise and demo the noise to the dealer's service manager and get the noise resolved while the car still has as much warranty remaining as possible.

Remember, if anything fixed under warranty you do not get the usual 2 year, 24K mile warranty in parts/labor but whatever time/miles remain of the car's current warranty.

Thus you want the source of the noise id'd pronto. You want the cause fixed pronto. You want to drive the car as much as reasonably possible after you get the car back after being fixed to give the car a thorough shakedown to make sure the symptom doesn't reappear.

You'll have plenty of chances to diagnose noises from the car after the warranty runs out.

Maybe.

Sincerely,

Macster.

Type_LT

Thanks gentlemen, I'll send her in next week for oil.

The recipe to recreate the noise is to just make sure it's warm, and then reverse for a few meters up a hill. Which is what I do every day when I back in the garage.

Type_LT

The sound in this video was later diagnosed as an IMS failure, sure sounds familiar!

http://www.youtube.com/watch?v=qQ8mN...eature=related

Macster

Nothing in the link.

You posted the noise has been coming and going for 6 months. If it is an IMS bearing it is taking its sweet time failing.

Sorry, ill-advised attempt at humor.

Seriously, the noise could be IMS but no one here can offer anything more than a well-intentioned and possibly educated guess.

Even if someone guesses right that doesn't make the noise go away. Some mechanic will have to at some point have to fix the problem that is causing the noise. And he's going going to want to do his own diagnosis. As it should be. You really don't want to walk in and tell a mechanic do this cause someone on the 'net says that's the problem. If he's worth having as your mechanic he's going to want to make his own diagnosis.

Now it might be, probably is, I hope it is, something relatively minor. But whatever it is it ain't going to fix itself.

And I might end with by continuing to delay taking the car in when you know how to reproduce the noise could be doing more harm than good.

You could see the engine progress from just a bit feverish to very sick or even dead.

No noisy engine ever got better by running the engine.

Sure there are exceptions which I won't cover now but they are very few and far between. And before I did run the engine I'd want an expert's opinion that that was the right thing to do.

You can bet there there are many more cases where by continuing to run the engine things got worse before they got better.

Sincerely,

Macster.