A hydraulic clutch not fully disengaging can be caused by a variety of reasons, the following are some common failure points and possible causes:

First, the clutch pedal free travel problem

Excessive free travel: The free travel of the clutch pedal is the distance that the pedal can move without applying force. If the free travel is too large, it will lead to incomplete clutch disengagement.

Second, the problem of release lever and support

Bending and deformation of the release lever, loosening of the support, or dislodging of the support pin: these problems make it difficult to adjust the height of the inner end of the release lever, which in turn affects the disengagement effect of the hydraulic clutch.

The height of the inner end of the release lever is inconsistent or too low: this will also affect the normal separation of the clutch.

III. Release Spring Problems

Individual release springs are fatigued, have insufficient height or are broken: the release spring is an important part of the clutch, and its condition directly affects the clutch's release effect.

Follower disk and friction plate problems

Follower plate warping, friction plate rupture or rivet loosening: these problems will cause the clutch to produce resistance when separating, thus affecting its separating effect.

Newly replaced friction plate is too thick or the follower plate is incorrectly installed: this may also lead to incomplete clutch disengagement.

Clutch friction plate wear: excessive wear of the clutch friction plate will lead to a change in the clutch engagement point, which may make the clutch start to engage early at a certain point of the pedal stroke, thus not being able to completely disengage.

V. Hydraulic maneuvering system problems

1. Air in the hydraulic system: the presence of air in the hydraulic system will cause the clutch pedal to feel “soft” or “empty”, affecting the normal operation of the clutch. The presence of air reduces the efficiency of pressure transfer from the hydraulic fluid, resulting in incomplete clutch disengagement. 2.

2. Insufficient or contaminated hydraulic fluid: A low hydraulic fluid level or poor oil quality (e.g., contamination or discoloration) will affect the performance of the hydraulic system. The cleanliness of the hydraulic fluid is critical to the proper functioning of the clutch.

3. Leaks in the hydraulic system: Leaks in the master cylinder, slave cylinder or in the hydraulic lines can cause a drop in hydraulic oil pressure and

affect the clutch's ability to disengage. Check all connections and seals for signs of leakage.

4. Damaged hydraulic system components: Damage to the master cylinder, slave cylinder or any part of the hydraulic lines, such as piston sticking, damaged seals, etc., will affect the normal operation of the hydraulic system.

Six, the engine and transmission problems

Engine bearing wear or damage: this will lead to the engine crankshaft and transmission input shaft is not the same axis, which in turn affects the clutch release effect.

Seventh, the hydraulic throwout bearing problem: 

Hydraulic throwout bearing internal wear or damage may also lead to the clutch can not be completely disengaged. This may require replacing the hydraulic throwout bearing with a new one.

Other Factors

Loose adjusting shims or set screws between the clutch cover and the flywheel: This can affect the overall working condition of the clutch.

Serious oil, dust and grease between the release bearing sleeve and its conduit: this will cause the release bearing to fail to return, thus affecting clutch disengagement.

Improper adjustment of the clutch pressure plate: Improper adjustment of the clutch pressure plate, such as insufficient spring tension of the pressure plate, may also result in the clutch failing to disengage completely.

Solution

1. Check and adjust the free travel of the clutch pedal: Make sure the free travel is moderate, not too big and not too small.

2. Check and adjust the height and consistency of the release lever: Make sure the height of the inner end of the release lever is consistent and works properly.

3. Check and replace damaged breakaway spring: Make sure the breakaway spring is in good condition.

4. Check and replace damaged follower plate and friction plate: Make sure that the follower plate and friction plate are flat and free from cracks and looseness.

5. Check and repair the engine support: make sure the engine crankshaft is coaxial with the transmission input shaft.

6. Clean and maintain related parts: clean and maintain the clutch and its related parts regularly to ensure that they work properly.

7. Venting: Perform hydraulic system venting to remove air from the system. This usually involves repeatedly depressing the clutch pedal until there are no air bubbles in the hydraulic fluid exiting the hydraulic throw bearing's vent port.  

8. Check Hydraulic Fluid: Check the level and cleanliness of the hydraulic fluid and change the fluid if necessary.

9. Check for leaks: Check all connections and seals of the hydraulic system for leaks, repair or replace damaged parts.  

10. Adjust the clutch pedal: Adjust the free travel of the clutch pedal and the position of the release fork according to the instructions in the vehicle owner's manual.  

11. Professional Inspection: If the above steps do not resolve the problem, it is recommended that the vehicle be taken to a professional repair store for inspection and repair. It may be necessary to replace the hydraulic throwout bearing, clutch friction plate or other damaged parts.

In summary, the reason why the hydraulic clutch cannot be fully disengaged may involve a number of aspects, which need to be investigated and solved one by one according to the specific situation. If the problem is more complicated or cannot be solved by yourself, it is recommended to seek the help of a professional mechanic.

Through the above steps, you can diagnose and solve the problem of hydraulic clutch not fully disengaging to ensure the normal operation of the clutch system and driving safety.