2002 996 Turbo Engine "Noise"

[rlcummings]

This is my first post, so I don't know if I am in the right forum for this question. I have a 2002 996 Twin Turbo with 20k or so miles. It has developed a rattling noise at low idle (a little like sheet metal rattling or something loose), though it seems to go away when the engine is rev-ed up. Normally, I would have expected an IMS bearing problem, but I understand that this particular engine isn't the same as the 996s which apparently have problems with their IMS bearings. I removed the serpentine belt, to see if one of the accessories was making the noise, but no luck. I've tried a stethoscope to listen around the engine and transmission, but the noise appears to not come from any particular area. Any ideas for where to look with such a general set of symptoms?

Thanks!

[CKPTAuto]

Is the problem worse when cold? Perhaps a lifter going bad?

[rlcummings]

It's always there when it is cold or warm at idle, but I can't tell if it goes away when I rev the engine because the engine noise drowns it out. Very perplexing for someone new to this model. I wonder if the Durametric tool might be able to point out an internal problem that might help point me to the cause. Haven't used one, so I don't know how effective they are in pinpointing internal engine problems like a bad lifter. Engine seems to run fine, with lots of power (just very noisy an rattlly at idle). Thanks for your help.

[blockhed]

change oil weight, it's normal, yes some of these sound like diesels

[Shadetree930]

It may be the typical turbo rattle that is common to this particular engine. Do a search on turbo rattle over on Rennlist or 6speedonline. More (relatively speaking) 996 traffic over there. This forum is pretty much focused on air-cooled turbos.

[Porschephd]

The noise is normal. The gears on the intermediate shaft are very noisy in this motor. It's a common noise with these motors especially after they are up to temp and sitting at idle. Nothing to worry about.

[rlcummings]

Originally Posted by blockhed

change oil weight, it's normal, yes some of these sound like diesels

Thanks for the feedback. Sorry for the late reply, I've been busy replacing a water pump and water cooled alternator on my BMW 750il since my initial post. I've learned a little more about the noise since the initial post. I did change my Mobil One oil to 10-40 and "watched" the sound as the engine warmed up. It did get quieter when the engine got up to normal operating temperature, but then seemed to come and go each time I rev'ed the engine. I did notice that noise tended to go away when I let the clutch out, so I thought that the cause may have been the new clutch disk rattling on the spines as was suggested (or perhaps the transmission gears simply engaged and quit rattling. In any event, the 3-4 posts that have been provided have really helped relieve some of my initial concerns about so much noise in an engine with only 20k miles on it. Now that I know that these engines can rattle like my F350 diesel truck, I can relax a little. Thanks again for taking the time to help me out.

[rlcummings]

Originally Posted by Shadetree930

It may be the typical turbo rattle that is common to this particular engine. Do a search on turbo rattle over on Rennlist or 6speedonline. More (relatively speaking) 996 traffic over there. This forum is pretty much focused on air-cooled turbos.

Thanks for getting back to me. Glad to know that my "rattle" is probably normal for these engines. I'm not used to this type of noise from a Porsche engine, but I do remember my early 911's really making a racket when the hydraulic timing chain tensioners stated giving up the ghost. Thanks again for pointing me to the other more appropriate forums on water-cooled turbos. I must admit that it's been a long, long wait before I finally got my first turbo, but it was definitely well worth the wait. It's hard to believe it is actually sitting out in my garage as we speak!

Take care.

[rlcummings]

Originally Posted by Porschephd

The noise is normal. The gears on the intermediate shaft are very noisy in this motor. It's a common noise with these motors especially after they are up to temp and sitting at idle. Nothing to worry about.

Stephen:

My apologies for not getting back to you sooner, but I've been busy wrenching on another "troubled vehicle" in need of some new accessories (water pump an water cooled alternator, etc.). My rattle is pretty evident at idle, but seems to go away when the engine is rev'ed and/or the clutch is engaged and the car moves forward in gear. Thanks for taking the time to point me in the right direction regarding its cause. I'd been reluctant to drive it much until I had better idea of what was the case. I initially thought it might have been the IMS bearing (until I found out that the engine in my turbo is not the same engine/case as in the non-turbo Carrera's). That was a relief (but a couple of days of wasted research on how to correct the problem). That said it was a relief to not have to drop the transmission again, after I'd just put a new clutch in just a short time ago. In any event, I intend to continue to "watch" the noise and will go over to the other forums to continue to "study" the nature of these "new rattles" to my experience base.

bought my first Porsche while stationed in Germany in 1970 and have really enjoyed a wide variety of them from my one-owner 55 speeder to my current 2002 Turbo. They never cease to put a smile on my face when I go out into the garage to take the out for a spin.

Take care, and thanks for taking the time to give me a hand.

Bob C.

[rlcummings]

Thanks for getting back to me. I did change the oil as you suggested. Nice to know that my Ford 350 diesel pickup will have some "noise competition" out in the garage. Take care