gear box noise after engine shut down

Vincent,

It was from your previous post ....


Here's some pics from the 348 dual mass flywheel. the rattle is a tell tale sign of impending failure, then you start having hot start problems. As far as I can tell this was more of a problem for th e348's than the 355's.

I'm trying to understand the connection between the clutch rattling, and the engine firing up (hot start problem).

Regards,

Pete

 

The dual-mass flywheel also serves as the harmonic balancer. When the input shaft seals go bad, leaking gear lube into the flywheel, the internal Kluber grease loses its viscosity and begins to sling out of the bell housing. When the hot engine and flywheel is re-started after the remaining grease/gear lube has pooled with gravity, this supposedly causes vibrations through the crankshaft which in turn fools the rev sensors at the crank. This makes it difficult for the ECUs to establish correct ignition timing and yields difficult starting when hot.

 

Peter: It's a good question. It's hard to believe that there is a relationship between the flywheel and the hot start problem, but it's true. Apparently, when the grease in the flywheel begins to get diluted and leak out (more so when the engine is hot and the viscosity may be reduced), the flywheel begins to go out of balance as the internal parts are no longer "damped" properly. Hence the rattling noise at cranking speed or low RPM, when the flywheel components are not under full load at full travel. The engine timing sensor and the TDC/revs sensors compare notes and send a signal to the Motronic ECU that the engine is out of balance and should not be allowed to start. You have to keep cranking until the sensors detect that engine is within the stated parameters, then it starts.

Someone with more technical knowledge than myself could give you more specific details, but that's the gist of it. Instead of spinning smoothly on the starter, the engine is actually spinning in a series of "jerks" as the play in the flywheel is taken up against the springs and released.

 

I meant impending FW troubles. The clutch may be just fine.

Ditto on what Jeff and Shan have just posted. My hot start problems dissapeared once I repacked the FW.

 

My hot start problem was 100% cured by repacking the flywheel, same as Vincent.

 

This is true and it was a surprise to me as "official" mechanics told me it couldn't be true.

Here was my original question on my 348.

I still would like to know how the design is different on the 355 or if it is/

http://www.ferrarichat.com/discus/messages/256120/252357.html