Hey all,


I own a 2004 996 C2 which I've owner for about 2 years and bought from the original owner. Aside from what I describe below the car has been driven basically everyday.

The car was shipped to Europe last summer so it sat for 3 months at port/on ship. After picking it up from the port and driving ~400 miles, I noticed a loud rattle which I assumed not to be IMS - from what I've read a rattle that loud from IMS means the engine is already toast.

After that it was driven for 2 weeks, then stored again for 4 months. For the last month it has been driven daily and on some long trips. Since the rattle developed, it has been driven roughly 2000 miles, about 1500 of which were in the last month - this is mostly high speed, high load autobahn driving... Last night I changed the oil and both the filter and the oil were completely clean - no metal whatsoever.

The rattle itself is a metallic sort of "marbles in the crankcase" type sound, and its rather inconsistent - it gets louder and softer without changes in RPM. It really sounds like a loose vibration somewhere. I will make a video later, but the closest sound I have heard so far is this:
I don't think this could be IMS given the amount of miles on the car since the rattle developed and the lack of metal shavings. Plus, people say when you hear this rattle the engine is completely trash in a matter of seconds - I have driven a lot of miles.

Any ideas/suggestions? It does not sound like lifter or valvetrain noise... I'll get a video and try to see how RPM dependent is soon.

 

First why are you driving your car around with an unidentified "unusual rattle" happening? Second if you're driving around, you're engine isn't "toast". It's likely not an IMS failure because- it hasn't failed. I would find someone who can tell you whether you have a loose nut or an impending problem - before I drove it any more.

 

Because I am taking the risk that the unusual rattle is something trivial rather than serious. To me it sounds like an exhaust rattle or flywheel chatter.

I am just trying to rule out IMS (90% sure), and then take suggestions from anyone on the boards who might know what it is. Someone suggested it might be loose bits in the mufflers, so I'll whack them around with a mallet later today and see.

It's also a lot easier to post on a forum than find a mechanic in a city you just moved to when you speak almost none of the local language... Back in the US I would just drive the 10 blocks to my indy shop. When abroad it's not quite that easy.

 

Waterpump about to blow?

 

For whatever it's worth, I used to own a 996 and I had a rattle in the rear and it turned out to be the driver's side muffler. It did not sound like the video you posted.

 

The rattle turned out to be the catalytic converter.

 

Was the cat bad or just loose?

 

O2 sensor data from the durametric (and the error code) show the cat is bad.