What are the causes of clutch master and slave cylinder faults? How to perform a drain check on the clutch master cylinder and slave cylinder?

The clutch is a component in the automotive transmission system that is directly connected to the engine. It is responsible for disconnecting and engaging the power and transmission systems, thus ensuring a smooth start of the vehicle. The master brake can also guarantee smooth gear shifting and prevent the transmission system from overloading. Below, China Auto Online School will share with you the causes of faults in the master and slave pumps of the clutch and the methods to empty the clutch!

What are the causes of faults in the master and slave pumps of the clutch? How to conduct a drainage check on the master cylinder and slave cylinder of the clutch? 

I. Causes and Solutions of Clutch Master and Slave Pump Faults

The clutch does not disengage completely, making gear shifting difficult. After adjustment, it malfunctions again after being driven for a period of time

Reason: (1) The clutch pedal and the eccentric pin nut connecting the master pump are loose; (2) The nut of the main pump push rod is loose; (3) There are problems with the pressure plate and driven disc of the clutch driven disc assembly.

Solution: (1) Tighten the eccentric pin nut; (2) After adjusting the clearance of the push rod nut, tighten it. (3) Replace the new pressure plate or driven plate.

2. The clutch is heavy, the clutch cannot be separated, and gear shifting is difficult

Reason: (1) The air inside the sub-pump has been completely discharged; (2) The clearance of the push rod of the main pump is too large, resulting in insufficient effective stroke of the sub-pumps. (3) The elastic deformation of the sub-pump bracket is large, which reduces the effective stroke. (4) The welding Angle of the clutch disengagement rocker arm is out of tolerance, resulting in a significant deviation in the center distance between the flange end of the connecting slave pump and the fork hole of the disengagement arm. Additionally, due to the inability to adjust the slave pump push rod, the stroke is insufficient. (5) Excessive clearance of the shift connecting rod mechanism causes resistance; (6) The separation bearing is not lubricated and the inner hole is roughened. (7) The main pump and the sub-pumps do not match.

Solution: (1) Drain the undrained air; (2) Adjust the pump push rod to the optimal effective stroke; (3) Re-reinforce the sub-pump support; (4) Re-weld to reduce the Angle error between the separation arm and the center distance; (5) Replace the shift connecting rod mechanism; (6) Replace the roughened related parts and add lubricating oil. (7) Replace the main pump with one that matches the sub-pump.

3. The clutch pedal becomes heavier and higher the more you press it, causing it to slip

Reason: The push rod of the master pump was adjusted downward too much, causing the check valve of the piston to close. The pressure oil in the slave pump cannot return, and in severe cases, the clutch plate may be burned out.

Solution: Readjust the clearance of the push rod.

4. The clutch pedal is pressed to the bottom and is hard and not in place, making it impossible to disengage

eason: The push rod of the sub-pump was adjusted too much.

Solution: Readjust the clearance of the separation push rod.

5. Air leakage in the sub-pump

Reason: (1) The air path is not clean. The sealing surface of the air valve inside the pump is stuck by foreign objects and cannot be sealed. (2) The working environment is harsh with excessive dust, causing premature wear of the inner ring of the cylinder. (3) The main pump does not return to its original position completely, and the check valves in the sub-pumps are not sealed.

Solution: (1) Clean the foreign objects in the cylinder, add lubricating oil, and replace the damaged seals; (2) Inspect and replace the main pump.

6. There is no feeling when stepping on the clutch, and the release pump has no response

Reason: (1) The oil passage is not clean, and foreign objects get stuck on the sealing surface of the check valve of the master pump, causing the master pump to have no response. (2) Due to pipeline leakage.

Solution: (1) Remove foreign objects and replace the damaged seals; (2) Repair the leaking oil pipe.

7. Clutch slipping caused by other reasons

Reason: (1) Severe overloading, exceeding the friction force of the clutch plate; (2) If the driver keeps his foot on the clutch pedal for a long time or the road conditions are bad, the clutch will wear out prematurely. (3) The clutch plate is defective. After heating, the friction force is insufficient, and the pressure plate force is uneven, resulting in unilateral wear or slippage due to grease contamination.

8. The slave pump returns to its original position slowly and the clutch does not disengage completely

Reason: The diameter of the connecting oil pipes of the main pump and the branch pump is small, and the separation bearing is scratched.

Solution: (1) Replace the hose with a diameter (inner hole) of no less than 6mm; (2) Replace the damaged separation bearing, bearing cover and related damaged parts.