Clutch Master Cylinder
A clutch master cylinder is actually a container that holds fluid and controls the pressure that is applied to the clutch when a driver steps on the clutch pedal to shift gears. As the clutch master cylinder takes in the pressure from the clutch pedal being compressed by the driver's foot, the slave cylinder boosts the pressure of the fluid in the clutch master cylinder to the point where it can engage or disengage the clutch. In other words, physical pressure from the person's foot is converted into hydraulic pressure to operate the clutch in a hydraulic clutch system. You'll find the clutch master cylinder is typically located on the firewall of the vehicle behind the engine and usually next to the brake master cylinder. These two master cylinders are usually located so close together under the hood of the vehicle because they are located side-by-side on the inside of the vehicle.
If you step on your clutch pedal and it feels spongy or falls to the floor that means that the clutch master cylinder has failed or needs more fluid to keep the hydraulic system working properly. The clutch assembly on a vehicle transmits the power that is produced by the engine to the gearbox. It also disrupts that power flow when the clutch pedal is depressed. The clutch master cylinder is attached directly to the clutch pedal. When the power that is produced by the engine is interrupted by the clutch master cylinder operation, it allows the vehicle to change gears. For instance, if you want to change your gear to neutral at a stoplight, you need to step on your clutch pedal so that the master clutch cylinder will allow you to change gears. If the master cylinder is not working correctly it will be almost impossible for the driver to shift gears unless they are skilled in the process of shifting gears without using a clutch.
If your clutch master cylinder needs to be replaced you will need to disconnect it from the clutch pedal. You will also need to remove the hydraulic lines that carry the fluid to the clutch master cylinder and slave cylinder. It is always a good idea to replace the slave cylinder at the same time you are replacing the master clutch cylinder. This will be a more economical for you in the long run. Also when you replace the master clutch cylinder you should also flush out all of the clutch fluid until it is clean and clear. The reason you should flush your entire clutch fluid system is to prevent water buildup or air pockets from being in the hydraulic lines.
You can always tell when the clutch master cylinder needs to be replaced because the vehicle becomes increasingly more difficult to shift gears. If you continually have low levels of clutch fluid or need to top off the fluid more often than usual, it usually means that there is a problem with the master clutch cylinder also. If you have dirty fluid in your master clutch cylinder that usually means that the internal seals are bad and are allowing dirt into your hydraulic system. Also, if you have fluid leaks from the rods that exit the clutch master cylinder, or if the master cylinder itself is leaking, you should consider replacing it.
Sometimes people don't want to replace their whole master clutch cylinder and will try to use kits to repair it. However these kits do not replace the internal parts of your master clutch cylinder and will not totally solve the problems you are having with your clutch's hydraulic system. It is much easier and less costly in the long run if you just replace the whole entire clutch master cylinder to begin with.
