mikemdd

I have a 997.1 GT3 with 6K miles. Zero incidents of rev over run during PPI. When the engine is hot there is a something between a "knock" or "rattle" coming from the rear of the engine on the drivers side. When cold, it sounds a little noisy, but nothing like when the engine/oil is hot. Almost sounds like ball bearings rattling around inside (not nearly that bad, but that kind of sound). It is only at idle, although when off idle, it is hard to hear anything. Also, it is almost more obvious when in the car with the window down, vs. when outiside. I have to say when sitting next to someone at a light, it is a little embarrassing to hear the engine sound like that. Again, I make it sound real severe (it is not), but it is something that someone who is mechanically oriented would notice.

As it is still under warranty, I am taking it to the dealer on Monday. However, I am guessing they will say "they all do that....". In any case, I want to get it on the record now that I had them look at it, in case something happens later. Anyone else have this issue? Any ideas what it could be (even if "normal"), coming from the rear corner of the engine on the drivers side?
(Note: I did a search on multiple forums and did not see my issue for the GT3 engine)
I appreciate any comments. Thanks.

Macster

In spite of where you say the noise is coming from, if the car is equipped with a manual transmission it can be clutch disc/transmission input shaft/gear rattle.

A quick way to tell if this is the case is to when you hear the noise is to fully depress the clutch pedal and see if this has any effect on the noise. If it is the clutch disc/input shaft/gears rattling about then the noise will go away and based on my experience with various cars that exhibit this noise (my 03 Turbo being the latest) it will not reappear when the clutch is released, until the next time the car is brought to a stop and the engine left to idle with the transmission in neutral and with the clutch released.

If the car does not have a manual transmission then...

Possibly a serpentine belt idler roller bearing or even a tensioner roller bearing or even one of the accessory drives, like a water pump.

Depends upon where the noise is coming from and this can only be determined by listening to the car and the engine while the engine is running.

The best thing I can advise is to if you can be there when the car is put on the lift and watch the techs id the source of the noise, the region from where the noise is coming from. Unless the source of the noise is obvious the techs will probably resort to using a mechanic's stethescope to more precisely determine where the noise is *not* coming from and where it is probably coming from.

Knowing where the noise is coming from really cuts down on the possible sources of the noise.

Oh, make sure you get a copy of a work order/invoice/estimate -- some official piece of paper from the dealer/service department with all the blocks are filled out: your name, car details including its VIN, date/time, odometer miles, a sentence or two describing the noise and when it occurs and so on. And get something after the car has been looked at the details what was done and when. It helps if you can be there so if you hear the noise and bring it the tech's attention if you're told they all do that you can at least have something that proves the tech's heard something and dismissed it.

BTW, if you're told they all do that then ask another/similar car be brought in and the same noise demo'd to you.

I don't think it will come to this but ready with a comeback just in case.

Sincerely,

Macster.

mikemdd

Thanks very much for the detailed response. I will check the transmission idea when I get home. It sounds pretty specific to the rear quarter of the engine on the drivers side, but could certainly be somewhere else. I like the idea of asking them "where the noise is coming from", even if they say it is "normal". At least this makes them do something other than send my on my way. Finally, hearing another car and getting documentation that they did something is also a great idea. Again, thanks.

BBMGT3

I recently had the idler bearings changed on my 997.1 gt3 because they were "noisy". I had just tuned out the sound as normal gt3 noise, but when I sent my car in for an oil change my shop swapped them out under warranty on their own accord. So, one of Macasters suggestions :-)

996FLT6

My pressure plate grenaded(driver fault) and sounded much like that rattle/knock at idle or at slow rpm. mike

jrgordonsenior

If not the TO bearing then how about the catalytic converter?....

avader906

check exhaust manifolds as well as exhaust itself for the leaks. if there are leaks there would be a pulse of hot air around that area. if you can borrow a stethoscope and listen for the noise - that would help. another area is one of the tensioner pulleys and/or waterpump. these are most common rattling noises. if it's waterpump - the noise will get louder and "grinder", if its exhaust - its more marbles - and could change if the car is warm/cold. if it's coming from the transmission - you would hear it from under the car. my bet would be on water pump / pulley.

mikemdd

Great feedback from everyone. I ruled out the transmission/clutch idea, as noted in the first post. I think it is significant it is only there when the engine has been driven and fully warmed up. If I put my palm on the oil filter or other parts in the area the sound is coming from, I can "feel" the noise. The fact that it is only there when fully warmed up is a factor, I'm sure. I'm probably beng overly dramatic and overly cautious, but it is not right. I'm taking it in to the dealer on Monday and will see what they say. I also head for Road America over Labor Day and want to make sure they don't say something happened there.

Macster

We can all offer possible causes of the noise and give you somethings to think about, somethings to consider, maybe even a few tests or checks you can do yourself, but unless you are prepared to do the full diagnostics thing and then of course the work to address what you find, almost always the car has to go to the shop for expert/professional evaluation and possible repair.

Hardly any engine noise ever gets better on its own.

I am not suggesting the source of the noise is super serious but only offering reinforcement that you are following the best course of action the only real course of action that makes the best sense for you and the car.

(In a shop today and encountered a 997 Turbo with a noisy engine (the engine was out of the car but I was told it was noisy) and the diagnosis is one intake lifter. Most of the time it is just one but standard operating procedure is to replace all intake lifters in the cylinder bank with the noisy lifter. Seldom is the noise due to a noisy exhaust lifter. The intake lifters are the only ones with the VarioCam Plus variable valve lift system (hydraulic valving) and this is what appears to be what goes bad.)

Anyhow, best of luck and if you can please post a follow up.

Sincerely,

Macster.

mikemdd

Update. Took the car in to the dealer this morning. Nice and warm when I arrived and the noise was there. Technician was called over to listen to it: "I don't hear anything. Sounds like all GT3's" Obviously, I disagreed. While discussing my disagreement, the Service Manager came over. He listened and trumped the Technician: "Something is definitely going on. Could just be exhaust or something in the engine, but needs to be looked at". He said they had two engines out of cars but would get it in when they were completed...maybe a couple of weeks and he would get it scheduled. I told him the warranty is up next month and he asked his guys to check when. They found it is up TOMORROW, not next month. He opened up a work order ticket and confirmed it would be covered by warrenty, if needed, even though they could not get it in now. I really lucked out on the timing. We will see what happens, but so far, I am pleased with the progress. Hopefully, it is something simple....or nothing at all.

avader906

Well - it's great they gonna take a look under the warranty. While there - when did you last changed your drive belt ? probably good idea if they change it now - and at the same time check all pulleys. everything else involves getting the car up on the lift running and some attention.

mikemdd

An update on the engine noise. It is at the dealer and the conclusion is that it is a bad lifter (See Macster's comments above). They have the engine apart waiting for parts. As noted, they will replace all the lifters in the left bank. I had the car up at Road America last weekend and it never missed a beat. However, the noise did seem to get a little louder by the end of the weekend. Anyway, the real proof will be when it is done and the noise is gone. But for now, the dealer has been outstanding in their service and support. Again, just made it under warranty by one day.

Mike