What is that sound when killing the engine?

It's probably the flywheel, but it shouldn't make a noise like this unless the Kluber grease inside the flywheel is either very diluted or has lost quite a bit of its volume. If you look under the back of the car, right in the center, you should see a small perforated panel on the underside of the clutch housing. Is there oil dripping from this panel? If so, you'll probably have to repack the flywheel before long, and replace the triple seals on the transmission shaft.

 

I've hear something like that too...at first worried me, but heard it on other 355's too so I figured it must be normal...

 

Mike, That's what mine sounded like when the cats went. I had a chunk of the core stuck in the muffler and it rattled like that. I'd check your cats as well.

Hope that helps.

Cheer's

 

I hear a rattle on my 355 when shutting down too. Always thought it had to do with the high compression ratio. No oil/grease dripping from the clutch inspection cover. Maybe much of it is gone already?? No cats. on my car.

 

Always heard it, and for sure it's not the cats - cats are fine, I inspected them.

 

Push the clutch when shutting off the engine. If the sound goes away, then it's in the tranny, possibly the flywheel ....

 

can you post a vid of this sound occuring?

 

You will need to remove the muffler to see inside the cats.

 

It's the flywheel...common issue in 355's. I push in the clutch when shutting down, so I don't have to hear it...no option for F1 owners...

 

Yep yep, I think so too.

 

Most likely the flywheel. I was tired of hearing mine rattle, so I popped it open, cleaned all the interior parts to the flywheel and re-packed it with Kluber grease in the amount specified in the manual (250g IIRC). Completely fresh, went for a drive - and it still rattled.

I believe what is going on is that as you drive the Kluber grease heats up allowing all the internal parts to move more freely, and on shutdown you hear all the plastic bits and springs rattle around.

As Jeff said, you may also have an issue with gear oil contamination - but I can confirm you may still get the "bag of rocks" experience even with a fresh R&R of the flywheel. Although the triple teflon seals get blamed for everything it is worthwhile checking the seals on the thrust bearing plate and the o-ring seal on the plate underneath it for the shaft bearing while you are in there.

 

My 355 has always make this noise. I have been told its the flywheel and nothing to worry about. I will have to try the clutch in thing to see if it doesnt do it with the clutch in. I was actually concerned once when this rattle disappeared.

 

I sometimes get a similar sound shutting off my 328, but to a lesser extent. No cat., just a plain Jane flywheel with no grease. (and no high compression like my 355 either). Hmmmm.........

 

same of my 355 ...will try depressing the clutch. What about the valves could that be an issue !

 

JH355 told me he suspects the springs in the flywheel are losing some of their tension. He has been thinking about designing some slightly thicker plastic pieces which retain the spring at each end on the flywheel. That additional tension might reduce or eliminate the rattle.

New springs would also eliminate the rattle at least for a time. But figuring a way to add a bit of tension to the old springs might be more permanent, since the old springs have already taken a "set" and unlikely to continue to lose additional tension.

 

Mike, I'm also sure it's your flywheel. If you have oil dripping from the clutch housing, you probably should plan to replace your slave cylinder/throwout bearing (A single unit) with one of the new Hill Engineering units. I just put new seals in my OEM one, and Daniel found the correct sizes I needed. But I plan to replace it with a Hill one, next time I'm in there. Also a couple small O-rings under the housing and triple seals as mentioned. Then repack the flywheel and you should be set! I still do get a little it of rattle once in a while, but not very often.
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I don't buy the cats story. You would know it if they went south. More rpms would make them hum and rattle. Also if you revved the engine, you would hear them vibrate. Depending on the failure, they would hum at different frequencies. Nah, it's something else. You could hope for the flywheel, but I'm with the trannie as the cause.

 

It could be your pilot bearings being really worn.

wait a second mike. did you leave a box of rocks inside the engine bay of your car???