Changing the flywheel is a complicated and time-consuming procedure. It requires disassembling the gearbox and the clutch assembly to gain access to the flywheel. When replacing the flywheel a good idea is also to inspect the bearing supporting the crankshaft and the flywheel seal and to replace them, if necessary. The most common flywheel failure is damage to its gear connected to the starter.
What is the flywheel and what role does it play?
The flywheel is mounted on the engine crankshaft, on the gearbox side. The role of the flywheel is temporary storage of the kinetic energy of the crankshaft in between the piston strokes. The flywheel allows the crankshaft to rotate while none of the pistons is in the stroke position. The flywheel is also equipped with a toothed ring, which catches on the starter motor in order to start the engine.
When should the flywheel be replaced and how is it done?
If damaged, the flywheel needs replacing. To this effect, the gear box and the clutch assembly have to be removed. Some cars are equipped with a dual mass flywheel comprised of two flywheels of a smaller mass, linked together by a torsional vibration damper. The damper damps the vibrations coming from the engine and prevents them from being transmitted to the gearbox and other elements of the drive system. The clutch has to be removed to gain access to the bolts holding the flywheel to the crankshaft.
What else to keep in mind?
When replacing the flywheel a good idea is to replace the bearing supporting the crankshaft and the oil seal located behind the flange. A new crankshaft is fitted in the reverse order. Another reasonable thing to do is replace the clutch in order to avoid having to disassemble the drive system again in the event of a clutch failure. It is difficult to tell the useful life of a flywheel, but the dual mass flywheels fitted on modern cars have a similar useful life as the clutch, i.e. about 100 thousand kilometres.