Dual Mass Flywheels

What is a Dual Mass Flywheel?

The flywheel is effectively a weight which is fastened to the end of the crankshaft of the engine. The power from the pistons tends to be created in “pulses” and the weight of the flywheel smoothes out these pulses by providing inertia to the rotating engine.

As well as providing a weight the flywheel has a gear around its circumference on which the starter motor operates and is a convenient means of attaching the clutch which provides a variable connection to the transmission.

Modern diesel and some modern petrol engines generate high torque and as a result they need extra smoothing out or “damping”. To help with this process a DMF (Dual Mass Flywheel) is fitted. This is effectively two flywheels that transmit the drive through a number of springs which cushion the drive of the transmission.

Is DMF failure inevitable?

No, not necessarily. Some vehicles cover very high mileages and do not have any problems.

Whether the DMF fails depends on what kind of duty the vehicle is subjected to and to some extent the way the vehicle is driven.

What happens when the DMF fails?

In practical terms, the first an owner will know is likely to be either a vibration and/or metallic jingling noise. The time these symptoms take to manifest themselves as a complete failure will vary dramatically. A complete failure will probably result in not being able to select any gears or in extreme cases a complete loss of drive.

However, it is recommended that is any of the symptoms described are experienced that the vehicle is taken immediately to a suitably equipped workshop for further investigation. This may avoid the inconvenience of a roadside breakdown and the associated recovery costs.

Can a Dual Mass Flywheel Be Machined?

The surface of a DMF can be successfully machined flat but due to the possibility of worn internals it is NOT recommended.

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