What is a Clutch Hydraulic System Bleed?
Many manual transmission passenger vehicles use the very reliable hydraulic clutch system. At a minimum, the system is composed of a master cylinder, which pumps fluid through a line, a flexible clutch hydraulic line, and a clutch slave cylinder. The fluid used is typically brake fluid, though there are several types in use. In order for the clutch hydraulic system to function properly and reliably, the clutch hydraulic system must be serviced and inspected regularly, including flushing and bleeding the hydraulic fluid to prevent corrosion, air, or water from causing damage in the clutch hydraulic system. Note that this system is not the clutch, it is simply how the clutch pedal in the vehicle is connected to the clutch on the engine flywheel. The advantage to a hydraulic clutch is that they are very easily pressed, and they can increase or decrease the range of motion needed to actuate the clutch.
What does the Clutch Hydraulic System do?
Flushing and bleeding the clutch hydraulic system is performed, most commonly, during normal factory scheduled maintenance. Brake fluid becomes contaminated over time, and will change from a clear, clean fluid, to a dirty, dark fluid. When the clutch hydraulic system fluid is dirty, it acts as a corrosive agent to the many rubber components of the clutch hydraulic system. Also, air or water in the clutch hydraulic system may necessitate component replacement. This will also require the clutch hydraulic system to be flushed and bled. Many technicians use a vacuum bleeder, a specialty tool designed to suck dirty fluid out of the clutch hydraulic system while new fluid is added to the reservoir. This tool attaches to the bleeder valve on the slave cylinder, and when the valve is turned suction pulls the fluid from the clutch hydraulic system system, preventing air from entering. Once the extracted fluid is completely clean, new and free of air, the valve is closed.
When should the Clutch Hydraulic System be Bled?
The prevalent cause necessitating flushing and bleeding clutch hydraulic system fluid is factory scheduled maintenance. However, if the fluid is noted to be extremely old, dirty, and hazardous to rubber clutch hydraulic system components, a flush and bleed service should be completed ahead of schedule. Also, when there is a clutch hydraulic system fluid leak, this service will be completed to remove air from the system once the leak is repaired. Lastly, if the clutch pedal fails to actuate the clutch, the clutch hydraulic system will be bled and flushed to eliminate air from the system. This will be performed after verification and repair of the source of air, and possibly beforehand in order to discover a small leak.