MINI Cooper Dual Mass Flywheel
 

I recently suffered an intermittent rattling noise coming from the clutch assembly in the front, drivers side of the car and was fairly certain that it was the release bearing as it would disappear as soon as you depressed the clutch.

However, it was unusual in so much as once a release bearing becomes noisy it usually stays that way. So the fact that on many days it was completely silent seemed odd. I also occasionally noticed it increasing with engine temperature. It wasn't a deep concern as it was happening with such infrequency and of course it would never misbehave when it was at the dealership for service. Well finally it did and was diagnosed as fitting the exact criteria of a Technical Service Bulletin for 05 vehicles that had faulty dual-mass flywheels.

To me, the flywheel has always been a simple device - a large, flat metal plate about 3/4 of an inch thick that is bolted onto the end of the engine crankshaft. It has a toothed gear around its circumference that the starter motor engages in. Designed to give the engine momentum and to assist with starting, there is a machined surface at the point of contact for the clutch, which is held against the flywheel by way of the clutch assembly. A spring-loaded pressure plate connects the car's gearbox to the flywheel by compressing the clutch plate between the flywheel and the pressure plate, conveying the engine's rotational force to the gearbox and subsequently to the car's drive train and wheels.

The clutch plate itself (the part that wears) is made of a similar material to brake pads and, when your in gear and driving, is pressed hard against the flywheel by the pressure plate. As you depress the clutch, a metal ring assembly that is around the the drive-shaft is pressed up against the clutch assembly and it compresses the springs releasing the pressure on the clutch plate and prevents transfer of power from the engine to the gearbox. You can then change gear, or stop the vehicle, without impacting engine speed. This assembly is called the release, throw-out or thrust bearing. Here is a great diagrammatic example of how this works. (Click on the following link for the complete article.)http://www.minimania.com/MINI_Cooper_Dual_Mass_Flywheel