Clutch Failures

How do you know if your clutch is failing? Since all automotive clutches fitted to manual vehicles perform the same function and work in the same way, the symptoms of failing clutches are also largely the same.
Note however that the severity of one or more of the symptoms listed below may vary between different makes and models of vehicles, as well as between different brands of clutches.
For the most part though, symptoms of failing, failed, defective, malfunctioning, or worn clutches are similar, so here are some examples...

Slipping clutch

A fully functional clutch forms a solid mechanical link between the engine and transmission, and therefore, it transmits all of the engines’ power to the transmission without any slippage, except for a brief moment during clutch engagement.
Provided the clutch is not allowed to slip by the driver though poor pedal control or sloppy driving technique(s), there is no relative movement between the flywheel, driven plate, and pressure plate when the clutch is fully engaged.
However, there are several reasons why a clutch might slip, which causes a hesitation upon take off, or an acrid, burning smell that results from overheating of the friction linings on the driven plate.

Both conditions may or may not be accompanied by an increase in the engine speed that is not matched by corresponding increase in the vehicle’s road speed, depending on the amount of slippage under any given set of operating conditions.

Note that slipping of a clutch can be caused by one or more of the following possible issues:

Difficulty in selecting gears

This is most commonly caused by a failure of the clutch to release fully, which means that the engine is not fully decoupled from the transmission. On most transmissions, the main shaft in the transmission needs to rotate fully independently from the engine to make gearshifts possible without damaging the transmission.

There are several possible reasons why a clutch may not fully decouple the engine from the transmission, including the following: On applications where the transmission input shaft locates into the crankshaft with a bearing or bush, the bearing or the bush may have seized onto the input shaft.
If this happens, the transmission’s main shaft rotates along with the engine, even though the clutch itself is in perfect working condition Some clutch manufacturers still use metal particles in driven plates’ friction linings as both friction modifiers and lubricants.

Unable to depress the clutch pedal

This is most commonly caused when the spring-loaded diaphragm in the pressure plate breaks. When this happens, one or more fragments of the diaphragm may move out of position and wedge themselves into the space between driven plate and the pressure plate’s outer shell in such a way that movement of the rest of the diaphragm is impossible.
Nonetheless, other causes could include the following:

Clutch vibration

Where a multi-plate clutch assembly is used in conjunction with DSG (Double-shift) transmissions.
It should be noted that while vibrations caused by single-clutch assemblies is relatively rare, violent vibrations caused by DSG (Double shift) transmissions, is a fairly common feature of these clutches.
However, clutch assemblies such as this are often used in conjunction with dual mass flywheels, and it is far more common for these types of flywheels to produce a vibration than for a DSG clutch to produce a vibration.
Dual mass flywheels consist of two parts, or masses; one mass is attached to the crankshaft, and the clutch assembly bolts onto the other part, and in practice, the two parts can rotate independently of each other- albeit only for about 60 degrees or so.
Like conventional clutch driven plates that contain cushioning springs in the hub, dual mass flywheels are also fitted with cushioning springs that perform the same function as the springs in conventional clutch driven plates.
As a practical matter though, vibration in dual mass flywheels is caused when the bearing around which the two masses rotate become damaged or worn, which can create huge imbalances.
If the problem is not corrected by replacing the flywheel, the vibrations can sometimes be severe enough to damage the clutch assembly, transmission, and other driveline components such as the differential and drive shaft(s).
It should also be noted that dual mass flywheels cannot be repaired; the only reliable remedy is replacement of the hugely expensive flywheel.

DSG (Double-shift) transmissions

DSG clutch issues could include the following:

In theory, both clutches are designed to be self-adjusting, but the practice is often somewhat different, and the failure of one clutch to adjust itself can affect an entire range of gears (odd-or even) or, in some cases, only some gears in a range.
Nonetheless, it should be borne in mind that a number of DSG clutch issues can also be caused by failures, malfunctions, defects, and faults in the actuators and control/monitoring systems that control the clutches.
As a practical matter, the best thing to do when any problem occurs on any DSG clutch / transmission combination is to seek professional assistance as soon as possible to prevent or reduce the chances of a relatively small problem developing into a potentially ruinously expensive transmission replacement.
If you are experiencing any of these issues, contact your local Repco Authorised Service Centre for advice.