What is the clutch master cylinder?

The clutch master cylinder is an important part of the transmission system in manual vehicles. It holds hydraulic fluid (uses brake fluid) which it pumps to the clutch slave cylinder on your manual transmission system in your vehicle.

The clutch master cylinder acts as a pump for your vehicle’s hydraulically operated clutch system.  When the clutch is engaged, hydraulic fluid is sent from the master cylinder to the slave cylinder so that the manual gearbox clutch plate can be disengaged and the gears can be changed. 


Causes of a failing clutch master cylinder

Your master cylinder has several seals that prevent hydraulic fluid (brake fluid) from leaking. These seals are prone to wear over time. As the seals wear, the clutch master cylinder becomes prone to leaks which can affect the distribution of fluid between your clutch master cylinder and your clutch slave cylinder on your manual transmission system. 

If the vehicle is not used for a long time, the clutch master cylinder seals may harden and be put under a lot of strain when the vehicle is next driven. This can increase the chance of the seals leaking. To avoid this, try to drive the vehicle every few weeks.

Also, the clutch master cylinder uses brake fluid as its hydraulic pressure fluid to the clutch slave cylinder.  Brake fluid is hygroscopic which means it absorbs water moister from the surrounding air over time. This means that over time this moisture in the brake fluid can cause corrosion to the clutch mater and clutch slave cylinders, which damages the internal piston seals. When this happens the clutch master and slave cylinder seals become more prone to leaking brake fluid.


Symptoms of a damaged master cylinder:

Difficulty shifting gears – A leak in the master cylinder will interfere with its ability to pump fluid to the clutch slave cylinder. This will affect its ability to engage and disengage the clutch when the pedal is pressed. For example, you may struggle to get the vehicle into first gear or reverse, and struggle to change gears while driving. 

Low brake fluid – A leak in the clutch master cylinder cause a decrease in your vehicle’s clutch fluid. Low clutch fluid will often cause reduced clutch effectiveness, making your vehicle difficult or impossible to drive.

Noisy clutch – When you press the clutch pedal down, you may hear a loud noise. This is caused by the clutch master or cylinders struggling to release the clutch, and holding too much hydraulic pressure constantly on the clutch lever, clutch trust bearing and clutch pressure plate. This can also be caused by the clutch slave cylinder piston being stuck too far out. 

Clutch pedal stuck down – If the clutch pedal is stuck down,  the hydraulics in your clutch system are not working. This is often caused by a damaged master cylinder.


Clutch Master Cylinder Diagnostics & Replacement in Hamilton

Clutch problems can become worse over time, resulting in more damage to your cars manual transmission / gearbox and ultimtley a higher repair bill. Therefore, it is best to get these problems fixed right away.

At Grimmer Motors, we can provide reliable, effective replacements for all parts of your clutch system, including the master cylinder. For reliable mechanics in Hamilton, contact us today!


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