Overview of hydraulic clutches

Hydraulic clutch definition:

A hydraulic clutch is a type of automotive clutch system whose main function is to connect and disconnect the power transmission between the engine and the transmission. Unlike traditional mechanical clutches, hydraulic clutches control the engagement and disengagement of the clutch through the pressure of hydraulic fluid, and have the advantages of compact structure, smooth operation, and rapid response.

Hydraulic clutch working principle:

1. Depressing the clutch pedal: When the driver depresses the clutch pedal, the pedal pushes the hydraulic oil flow through a small piston.

2. Hydraulic oil transfer: Hydraulic oil is transferred to the large piston in the clutch assembly through a pipe. 

3. Pushing the pressure plate: The large piston pushes the clutch pressure plate to separate it from the clutch disc (friction plate), thus cutting off power transmission.

4. Release the pedal: When the driver releases the pedal, the hydraulic fluid returns, the spring pushes the pressure disc back, the clutch disc re-engages and power transmission resumes.

 Hydraulic Clutch Failure

When the hydraulic clutch malfunctions, the following obvious phenomena may appear:

1. Abnormal clutch pedal:

   - Soft pedal or no resistance: If the clutch pedal feels soft and no resistance when pressed, or if it needs to be pressed very deeply to shift gears, this may mean that there is a problem with the hydraulic system of the clutch, such as fluid leakage or air getting into the hydraulic system, resulting in the clutch not working properly.

   - Longer pedal travel: If the clutch pedal travels longer when pressed down, i.e., it needs to be pressed deeper to disengage the clutch, this may be a sign of a worn clutch disc or insufficient pressure on the clutch pressure plate.

2. Clutch slippage:

   - The engine speed increases but the vehicle speed does not increase: when the clutch pedal is pressed, the engine speed rises rapidly but the vehicle speed does not increase accordingly, which indicates that there may be a slipping phenomenon of the clutch. Slipping is a typical manifestation of serious wear and tear of the clutch disc, which requires timely maintenance and replacement of the clutch disc.

3. Difficulty in shifting gears:

   - Difficulty in shifting gears: If the clutch is damaged, it may not feel smooth when shifting gears, especially when driving at low speeds. This may be caused by worn clutch discs, insufficient pressure on the clutch pressure plate or failure of the hydraulic system.

4. Strange noises:

   - Metal rubbing or rattling sound: If a metal rubbing or rattling sound is heard when the clutch pedal is depressed or released, this may be a sign that the clutch disc is worn out or the internal parts of the clutch are damaged.

5. Clutch Heat:

   - Pedal gets hot or smells burnt: When using the clutch for a long period of time, the pedal becomes hot or even smells burnt. This indicates that excessive frictional heat is generated between the clutch disc and flywheel and the temperature rises. Deformation and burning of the clutch disc, deterioration or rupture of the oil seal, and failure of the hydraulic system may cause the clutch to become hot.

6. Shaky start:

   - Uneven Clutch Plate Wear: Uneven clutch plate wear or hydraulic system problems may cause the vehicle to judder when starting.

7. oil leaks:

   - Poor sealing of the hydraulic system: Poor sealing of the hydraulic system can lead to oil leakage and affect the normal operation of the clutch.

 Maintenance and care of the hydraulic clutch

In order to ensure the normal operation and safety of the hydraulic clutch, regular maintenance and servicing is required as follows:

1. Regular inspection:

   - Hydraulic system: Regularly check the pipelines, cylinders, pressure gauges, etc. of the hydraulic system to ensure the normal work and safety of the hydraulic system.

   - Cardboard status: Check the cardboard status to ensure the sealing and tightness between the cardboard and the hydraulic clutch, as well as the safety and durability of the cardboard.

2. control pressure:

   - Avoid excessive pressure: When operating the hydraulic clutch, care needs to be taken to control the hydraulic pressure transfer and not to apply excessive pressure, which may cause damage to the equipment or injury to the operator.

   - Avoid overloading: Do not allow the hydraulic clutch to exceed the load it can withstand to avoid malfunction.

3. Stop the machine in time:

   - Discovery of abnormalities: In the course of using the hydraulic clutch, if abnormalities are discovered, such as high temperature, unstable pressure, etc., it is necessary to stop the machine in time for inspection and troubleshooting.

4. Cleaning and maintenance:

   - Regular cleaning: after using the hydraulic clutch, it is necessary to clean and maintain it and the related equipment to extend the service life of the equipment and ensure the safety of the equipment.

   - Keep clean: when cleaning, you need to ensure the cleanliness of the clutch and related parts to avoid oil and impurities damage to the clutch.

5. Filing records:

   - Operation records and maintenance records: File and keep the operation records and maintenance records of the hydraulic clutch for future enquiry and reference. This helps to identify potential problems and take appropriate measures to ensure the continued stable operation of the hydraulic clutch.

 How to judge whether the hydraulic clutch needs to be replaced

To judge whether the hydraulic clutch needs to be replaced, the following aspects can be observed and tested:

1. clutch pedal feel:

   - Soft pedal or no resistance: If the clutch pedal feels soft and no resistance when pressed, or if it needs to be pressed very deeply to shift gears, this may mean that there is a problem in the hydraulic system of the clutch, such as fluid leakage or air getting into the hydraulic system, which causes the clutch not to work properly.

   - Longer pedal travel: If the clutch pedal travels longer after it is pressed down, i.e., it needs to be pressed deeper to disengage the clutch, this may be a sign of worn clutch disc or insufficient pressure on the clutch pressure plate.

2. Clutch working performance:

   - Clutch slippage: When the clutch pedal is depressed, the engine speed rises rapidly but the vehicle speed does not increase accordingly, which indicates that the clutch may be slipping. Slipping is a typical sign of serious wear of the clutch disc, which requires timely repair and replacement of the clutch disc.

   - Difficulty in shifting gears: If the clutch is damaged, it may not feel smooth when shifting gears, especially when driving at low speeds. This may be caused by worn clutch discs, insufficient pressure on the clutch pressure plate or failure of the hydraulic system.

   - Strange noises: If you hear a metallic rubbing or crunching sound when depressing or releasing the clutch pedal, this may be a sign of a worn clutch disc or damaged internal clutch parts.

3. Clutch appearance and odour:

   - Burning Clutch Plate: If you smell a burning odour while driving, this could be a sign that the clutch plate is overheating. Prolonged high temperatures can cause the clutch disc material to degrade and affect its performance.

   - Severe clutch disc wear: By observing the wear of the clutch disc, you can determine whether the clutch needs to be replaced. If the clutch disc is badly worn and its thickness is obviously thinned, or if it is cracked or peeled off, it is necessary to replace the clutch disc with a new one.

4. Professional testing and diagnosis:

   - Pressure test: Use a clutch pressure tester to check whether the working pressure of the clutch is normal.

   - Wear test: Use the clutch wear tester to check the wear of the clutch disc.

   - Seal check: Check the seals of the hydraulic system and replace them promptly if they are damaged to prevent oil leakage.

 Initial Diagnostic Steps for Hydraulic Clutch Failures

When a hydraulic clutch malfunctions, the following steps are usually followed for initial diagnosis:

1. Enquiry and observation:

   - Communicate with the driver: find out the specific performance when the clutch is operated, such as the pedal feeling (whether it is too hard, too soft, or changes in travel), and whether it is difficult to shift gears.

   - Observe the free travel of the clutch pedal: Make sure the pedal has enough free travel when fully relaxed; too much or too little needs to be adjusted.

   - Check for signs of leakage: observe for traces of fluid.

2. Function test:

   - Check pedal travel: ensure that the clutch pedal has the proper amount of free travel, too much or too little requires adjustment.

   - Try to shift gears: Try to shift gears in a safe environment and feel if the clutch disengages and engages smoothly.

3. System Pressure Check:

   - Use a pressure gauge: Check the pressure in the hydraulic system, especially when the clutch is engaged, to determine if the pressure is normal. Abnormal pressure may be an indication of pump, line or valve problems.

4. Listen for sounds:

   - Listen for operating sounds: abnormal noises may indicate internal wear or damage to hydraulic components.

5. visual inspection:

   - Check hydraulic fluid cleanliness: contaminated fluid may cause the system to work poorly.

   - Observe leaks: Leaks can lead to insufficient system pressure.

6. Physical Inspection:

   - Check the sub and master pumps: look for abnormalities such as leaks or damage.

   - Check clutch disc wear: this may require disassembly.

7. Troubleshooting:

   - Check connections: make sure pedal connections are not loose.

   - Replenish hydraulic fluid: Try replenishing the hydraulic fluid and see if it improves.

8. Diagnosis without instrument exchange:

   - Temporary replacement parts: In the absence of specialised testing equipment, consider a temporary replacement of a healthy clutch part from the same model to quickly locate the problem.

 Summarise

As an important part of the automotive transmission system, the proper functioning of the hydraulic clutch is crucial to the driving safety of the vehicle. Therefore, we need to maintain and service it regularly to ensure its reliability and safety. Through the above fault performance, maintenance recommendations and preliminary diagnostic steps, you can find and solve hydraulic clutch problems in time to extend its service life and ensure driving safety. If complicated problems are encountered, it is recommended to go to a professional auto repair shop for detailed inspection and necessary repair or replacement work.