Introduction to clutches and clutch bleeding

 I. What is Clutch

A clutch is a device on a car, tractor or other machine used to connect or disconnect the power transmission between the engine and the transmission. Its main function is to control the combination and separation of engine power and the transmission system, to ensure that the vehicle can start smoothly, shift gears, and interrupt power transmission when necessary to prevent the transmission system from overloading.

 Working Principle of Clutch

The clutch transmits engine torque to the transmission through friction torque. Its core components include:

- Clutch Disc: Located between the engine flywheel and the clutch pressure plate, it is usually composed of friction material and metal structure. The function of the clutch disc is to provide friction between the flywheel and pressure plate to transfer engine power.

- Clutch Pressure Plate (Clutch Pressure Plate): responsible for transmitting power by pressing the clutch disk against the flywheel. The clutch pressure plate presses the disk by spring or hydraulic pressure.

- Flywheel (Flywheel): connected to the engine, the function is to store rotational kinetic energy and provide a smooth power output.

- Slave Cylinder: It controls the release bearing and pressure plate of the clutch through the hydraulic system, so that the clutch can work smoothly.

- Master Cylinder: It works in conjunction with the slave cylinder and controls the clutch action through hydraulic pressure.

 Types of clutches

1. Manual Clutch: The driver controls the disengagement and engagement of the clutch through pedal operation. This is the traditional type of clutch. 

2. Hydraulic Clutch: Uses a hydraulic system instead of a mechanical connection to provide a smoother operating experience and is usually used in modern automobiles.

3. Electronic Clutch: The clutch disengages and engages through an electronic control system, providing more precise control, and is commonly found in self-driving or high-performance vehicles.

Why clutch bleeding is necessary

In a hydraulic clutch system, air may enter the hydraulic system and cause the clutch to work improperly. The presence of air affects the efficiency of hydraulic fluid transfer, leading to the following problems:

- Softening of the clutch pedal: The presence of air prevents the hydraulic system from providing sufficient pressure, resulting in a soft clutch pedal feel and poor operating feel.

- Incomplete clutch disengagement: Air forms air bubbles which can be compressed at high pressures, resulting in inconsistent pressure transfer to the clutch and affecting its disengagement.

- Sluggish response: The presence of air reduces the responsiveness of the clutch, resulting in difficult shifts or uneven starts.

Therefore, the purpose of clutch bleeding is to restore the clutch's normal operating performance by expelling air from the system and ensuring that there is only fluid in the hydraulic system.

 Causes of clutch bleeding

1. System contamination: Over time, air may be mixed into the clutch hydraulic system due to aging, worn seals or leaks.

2. After repair: After replacing the clutch fluid, clutch master cylinder, distributor pump or related lines, air must be removed from the system.

3. Performance degradation: The presence of air will reduce clutch response speed and efficiency, affecting the driving experience.

 C. Clutch Bleeding Methods and Tools

Clutch Bleeding Kit

Clutch Bleeding Kit is a set of tools designed to facilitate the bleeding of the clutch system and usually contains the following components:

- Fitting and adapter: Used to connect to the bleeder screw of the clutch splitter pump to ensure a tight seal.

- Transparent Hose: Used to observe the discharge of air bubbles.

- Reservoir: Used to collect old or drained clutch fluid.

- Operator's Manual: instructs the user on the proper bleeding procedure.

 Bleeding Procedure

1. Prepare Tools: Make sure the clutch bleeder kit is complete and check that all fittings are in good condition.

2. Locate the bleeder screw: Locate the bleeder screw on the clutch master cylinder or distributor pump. This is usually a metal plug with a rubber seal. 3.

3. Attach tool: Attach the clutch bleeder kit adapter to the bleeder screw and connect the reservoir to the adapter with a clear hose.

4. Fill hydraulic fluid: Make sure the hydraulic fluid level in the clutch reservoir is within the normal range. If the level is too low, the hydraulic fluid will need to be replenished.

5. Pump out air: Open the bleeder screw plug and allow air and hydraulic fluid to flow out through the clear hose. Either use a hand vacuum pump or have an assistant repeatedly depress the clutch pedal until the oil coming out of the clear hose is clear and free of air bubbles.

6. Close the bleeder screw: When it is confirmed that there is no air in the system, close the bleeder screw and clean up the work site.

7. CHECK EFFECTIVENESS: After bleeding is complete, test the clutch feel and response to make sure the clutch system is back to normal.

 Precautions

1. Safety first: Before bleeding the clutch, please make sure the vehicle has been stopped and the engine is turned off, and pull up the handbrake to prevent the vehicle from sliding.

2. Professional operation: Clutch bleeding operation requires certain professional knowledge and experience. If you are not familiar with this process, please seek the assistance of a professional technician.

3. Keep clean: Keep the working area clean during operation to avoid impurities and dirt entering the clutch hydraulic system.

4. Regular inspection: In order to ensure the proper functioning of the clutch, it is recommended to check the oil level of the clutch hydraulic system and the condition of the seals on a regular basis. If any abnormality or leakage is found, please repair or replace the relevant parts in time.

Summarize:

The clutch is an important component in the vehicle's power transmission system, which transmits power from the engine to the transmission through friction torque. The entry of air into the hydraulic clutch system can cause the clutch to work improperly, manifesting itself in problems such as soft clutch pedal, incomplete disengagement or sluggish response. Therefore, clutch bleeding (air venting) is an important maintenance operation to ensure the proper functioning of the clutch hydraulic system. It is designed to discharge the air in the system and restore the pressure transfer capability of the hydraulic system, thus ensuring the normal working performance of the clutch.

Through proper bleeding operation, the air problem in the clutch system can be effectively solved to ensure a smoother and more stable driving experience. For vehicle owners, understanding the basic principles of the clutch and the bleeding method will help to better maintain the vehicle and extend the service life of the clutch. If you encounter complicated problems or uncertainties, it is recommended to seek the help of a professional technician.