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Clutches are the workhorse of the modern car. Located between the engine and transmission, the clutch is under ever increasing strain caused by more power, higher torques and weight. Ongoing trends, in particular, toward high-torque diesel vehicles are placing more and more demands on clutches. We, therefore, advise drivers to take their cars to the garage immediately if they notice seemingly minor problems like changes in
setting-off performance.

The average engine output in newly registered passenger cars in Germany has risen from 90 to 103 kW in the last ten years. The torques for more powerful diesel engines rose even higher. Nowadays, 400 Nm is no longer the exception. At the same time, vehicle weight has increased by an average of 50 kilograms over the same period.

All these advancements are placing higher demands on the clutch system which functions as the power transfer between the engine and transmission. We are also observing another phenomenon; Due to increased engine output, many drivers barely feel the tow loads that their vehicles are sometimes pulling. Even though powerful SUVs pulling two tons behind them do a pretty good job on hills, this kind of driving is very hard on the clutch.

Damage to the clutch system is quite common. What often seems to be a harmless problem in the beginning, such as kangarooing when setting off, can quickly turn into an expensive repair. If the clutch is permanently subject to overload for example, when driving a vehicle with a heavy tow load, the clutch can be damaged. Friction between the clutch disc and the clutch cover assembly or flywheel caused by overload can, in turn, cause isolated hot spots. These thermal hot spots increase the risk of cracks on the friction surfaces of the clutch pressure plate and the flywheel as well as damage to the clutch disc facing material. Furthermore, these hot spots can cause a complete failure of the dual-mass flywheel (DMF). Continuous exposure to heat of the special lubricant can cause it to harden. If this happens, the dual-mass flywheel has to be replaced.

In general, when replacing a clutch, it is important to carefully examine adjacent components. This can prevent further damage and a more complex repair, and minimise costs.

For vehicles with a hydraulically-actuated clutch, air in the system can also cause operating problems. Even worn motor bearings or a poor engine adjustment can be possible reasons for a change in the setting-off performance. If the source of the problem cannot be found in the immediate area, the transmission has to be removed and the clutch disassembled.

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