Clutch replacement & repair made easy

What does a clutch do?

The clutch on a vehicle is a friction plate which, when engaged, transfers the turning force of the engine, through to the gearbox and subsequently, the wheels.

How does a clutch work and what are the components?

When an engine is running, the pistons force a rotation of its crankshaft. At the end of this crankshaft is a flywheel. So all the time the engine is running, the flywheel is turning, like a spinning plate.

The clutch friction plates, when you release the clutch pedal, then press against this flywheel and transfer this turning force through the shaft into the gearbox. When the clutch pedal is pushed down, the clutch disengages from the flywheel and thereby slows or stops the gears from turning, allowing you to select another gear without grinding the gears together.

Whilst it may seem the clutch is a complex unit, it is in fact relatively simple in its base format. The components are a friction plate, a cover and a bearing, with a mechanism to “pull” it away from the turning flywheel. This mechanism can either be cable or hydraulically operated by the clutch pedal.

If you consider it, it works in the opposite way to a brake. Press the brake pedal down and it forces the brake pads onto the disc. Press the clutch pedal down and it releases the pad from the disc.

Clutch’s are replaced as a kit. The kit will comprise of the friction plate, the cover and either a release bearing or a concentric slave cylinder. This latter part, known as a CSC, is an internal slave cylinder on hydraulically operated mechanisms. As it is prone to wear, these are automatically replaced where they are present.

There are of course other, more complex versions, with dual mass flywheels, semi automatic gearboxes (where the manual operation of the clutch is replaced by electrically controlled solenoids), but in essence the actual end way it works is the same.

How do you know there is something wrong with the clutch?

If you drive a vehicle with a manual gearbox, at some point you will experience a clutch starting to wear, the same as you will with brake pads.

The friction material will start to wear thin and it will no longer provide sufficient contact with the flywheel and you will experience the clutch slipping, so here are some tell tale signs of this occurring;

• The engine speed will rise up rapidly, but you do not go any faster, especially up hill or under hard acceleration
• You notice an almost electrical sweet burning smell inside the car

Other symptoms though are prevalent

• You can engage a gear when the engine is off, but not when it is running
• The clutch pedal biting point (this is the point when you feel the vehicle moving from stationary for example) has become much higher up in the pedal travel
• You start to find it harder to move between gears and can often hear a crunch as you do so

When should you consider a clutch replacement?

Lets face it, if something is worn, it is not going to get better. Therefore if you start to experience any of the above symptoms, you are going to have to get the clutch replaced. The longer you leave it, the more likely it is that you could become stranded or, even worse, find yourself in a dangerous position on the road.

How common is a clutch replacement?

As with everything that suffers from wear and tear, it is not going to last forever. A vehicle with a manual gearbox is going to wear its clutch out at least once in its lifetime.

How can I extend the life of my clutch?

This is one area where your driving style and habits can indeed have a considerable effect on the components. By driving with mechanical empathy, not riding the clutch (leaving your foot resting on the pedal), not deliberately slipping the clutch to hold the vehicle on an incline and not using too high engine revs to pull away from a standstill are all ways to extend the life of the friction material.

What happens during a clutch replacement?

A lot of the process to change a clutch is vehicle specific, however there are a few standard steps

The mechanic will

• Raise the vehicle
• Split the gearbox from the engine
• Remove the old clutch unit
• Fit a new clutch kit
• Put everything back together
• Road test the vehicle

Do I have to change the flywheel at the same time?

Most modern cars, especially those with diesel engines, will have what is known as a dual mass flywheel (DMF). This is basically two flywheels held together with springs that reduce the vibration from the engine through the gearbox.

When a clutch is replaced, the DMF will be inspected for any damage or wear and if present, this will also require replacing otherwise the new clutch will not work efficiently and can cause it to wear prematurely. It isn’t actually possible to tell if it needs replacing until the clutch is removed from the vehicle, however, if you hear rattles from the clutch for example, or experience more vibration than normal, then it is a sign to expect this to also need replacing.

If the clutch has been slipping for some time, it may have also caused the rivets that attach the friction material to its backing plate to have been exposed and they will have scored the flywheel surface and that will also mean replacing it. Therefore if your clutch is starting to slip, do not try and delay the inevitable replacement as it could end up costing you nigh on double to have the DMF changed as well.

How much does a clutch replacement cost?

The cost of replacing a clutch depends on your car and what parts your car's manufacturer recommends using for the replacement. Find out what you could save by having your clutch replaced by ClickMechanic, by selecting your car at the top of this page!