If your car is fitted with a manual gearbox, it is essentially the driver's responsibility to select the proper gear for the road conditions ahead. In order to do this effectively, you will need to temporarily disconnect the power provided by the engine from the transmission system that turns the wheels. As you may know, this separation occurs when you put your foot on the clutch pedal, but sometimes this part of the system can fail. You may be able to identify what's going on by the specific noise, sound or action. What signs that you need gearbox repairs should you be on the lookout for?
How Does It Work?
A typical clutch system has several different moving parts but is usually made up of a number of disks, placed within a special housing and activated by bearings.
You may notice that the engine noise is rising, but that the car is not moving forward as it should. This is usually caused by the clutch slipping and you may also notice a burning smell at the same time. Usually, something has contaminated one of those internal plates and it's possible that a failure has allowed hydraulic fluid to come into contact where it shouldn't. This "slippery" fluid causes overheating and will not allow the transmission to engage properly according to the speed of the engine.
Conversely, you may notice that the clutch pedal itself feels spongy. In more modern vehicles, this indicates that the hydraulic fluid upon which it relies may have absorbed excess moisture. In the worst case, you will be unable to select any gears or may notice that there is a crunching sound when you try to do so. It's possible that this can be rectified by changing the hydraulic fluid first.
If the clutch pedal fails altogether, it may sink to the floor and stay there. In this case, it's likely that the slave cylinder seal has failed and all the fluid has been lost beneath the vehicle. In doing so, the pressure inside the system is also lost and thus the pedal will not return to its starting place.
Worn Release Bearing
If you depress the clutch pedal and hear a high-pitched screech, it could be that the release bearing has worn. As it is not functioning properly, it will not connect cleanly with the pressure plate inside the clutch and this friction will cause the noise.
Finally, you may notice a significant vibration when you move forward, or a strange "knocking" noise whenever you depress the clutch pedal. This could be due to a fault with the flywheel being out of kilter and will require attention as soon as possible.
What Should You Do?
Pick up the phone and explain what you think is happening to your mechanic so that they can advise you of your options ahead.