Service Procedures for Hydraulic Clutch Release Systems

This article provides instructions on how to service the different types of Clutch Hydraulic Release Systems for Cars and Pickups.

Hydraulic Bleeding of Master Cylinders and External Slave Cylinders with Bleed Screws

1. Carefully clean the top and sides of reservoir before opening to prevent contamination of the system with dirt, water, and other foreign material.

2. Remove the reservoir cap.

3. Remove the reservoir diaphragm when checking or adding fluid.

4. Fill the master cylinder reservoir with new clutch hydraulic fluid or an approved DOT 3 brake fluid. Do not use old fluid or any other types of fluids.

5. Depress the clutch pedal and hold it down.

6. Open the bleed screw on the slave cylinder to let air and clutch fluid escape.

7. Close the bleed screw and release the clutch pedal. Don’t over tighten the bleed screw. Note: Check and refill the reservoir as needed while bleeding the system to prevent air from being drawn into the system.

8. Repeat steps 5 thru 7 until all the air is out and the clean clutch fluid is visible.

9. After bleeding the system, pump clutch pedal several times. If clutch engagement is not satisfactory, repeat the bleeding procedure or bleed the system using the procedure for slave cylinders without bleed screws. Under normal usage, small amounts of air will eventually work their way out of the system.

Hydraulic Bleeding of Master Cylinders and External Slave Cylinders without Bleed Screws

1. Push the slave cylinder pushrod in and disconnect both retaining bands of the retaining strap. Release the push rod and allow it to fully extend. Do not cut or discard the retaining strap.

2. Tip the slave cylinder up at approximately 45 degrees and pour clutch hydraulic fluid into the hydraulic port until all the air has been expelled.

3. With the slave cylinder still tipped up, insert the clutch hydraulic tube in to the slave cylinder hydraulic output port (replace the small rubber seal on the end of the metal tube connector and lubricate it with clutch fluid), insert the retaining pin and drive it in with a drift punch.

4. Hold the slave cylinder vertically with the pushrod facing the ground. Hold the pushrod against the palm of your hand in a position that allows the slave cylinder to be lower than the master cylinder.

5. Slowly depress the pushrod into the slave cylinder bore approximately 25 – 30 mm while watching the master cylinder reservoir for air bubbles. Stroke the slave cylinder in this manner until air bubbles are no longer entering the reservoir, about 10 – 15 strokes.

6. With the master cylinder reservoir cap removed, slowly push the slave cylinder pushrod back in and reconnect the two bands of the retaining strap. The slave cylinder is now ready to be installed in the vehicle.

Master Cylinder – Removal and Installation

1. Disconnect master cylinder pushrod from the clutch pedal. Inspect and replace pedal pin bushing if worn or damaged.

2. If the safety interlock switch is fitted to the pushrod, disconnect the switch connector.
Note: Some Ford Aerostar vans require the master cylinder pushrod to be removed from the master cylinder before the master cylinder can be removed from the vehicle.

3. Using a 3mm (7?64”) diameter punch, drive out the retaining pin that holds the hydraulic tube to the master cylinder. Be careful not to damage the master cylinder body.
Note: On some vehicles the hydraulic line will have an in-line tube connector that can be disconnected using the hydraulic line Quick Connect tool.

4. On master cylinders having a remote reservoir, remove the fasteners holding the reservoir to the front of the dash.

5. Remove the two fasteners retaining the master cylinder assembly to the front dash. Note: On some vehicles a “Twist and Lock” type of attachment is used to secure the master cylinder to the front of the dash. To remove the master cylinder with this type of attachment the master cylinder body must be rotated approximately 45 degrees clockwise except for Saturn vehicles, which require a counterclockwise rotation. The front of the dash or bracket is keyed so the master cylinder can only be reinstalled with the correct body and reservoir orientation. When reinstalling a master cylinder with this type of attachment be careful not to over rotate the master cylinder or damage to the body will occur.

6. Carefully remove the master cylinder from the front of the dash.

7. For reinstallation, complete steps 1 through 6 in reverse order.

8. Bleed the master cylinder per the Hydraulic Bleeding instructions.

Concentric Slave Cylinder – Removal, Installation, and Bleeding

1. Disconnect the hydraulic tube coupling at the transmission with the hydraulic line Quick Connect tool by sliding the white plastic sleeve toward the slave cylinder.

2. Remove the transmission per your vehicle manufacturer’s Shop Manual.

3. Remove the bolts retaining the concentric slave cylinder to the transmission.

4. Remove the concentric slave cylinder from the transmission.

5. Clean the transmission input shaft and install the new concentric slave cylinder. Make sure the slave cylinder is installed flat against the transmission mounting surface.

6. Install the slave cylinder attaching bolts (if required) and tighten to the vehicle manufacturer’s Shop Manual requirements. Check to make sure the slave cylinder is not cocked.

7. Install the transmission per your vehicle manufacturer’s Shop Manual.

8. Inspect the hydraulic tube coupling for damage and contamination, replace the “O” ring and lube with clutch fluid.

9. Reconnect the hydraulic tube by inserting the male coupling into the female coupling on the slave cylinder. Make sure the coupling is secure.

10. Carefully clean the top and sides of the reservoir before opening to prevent contamination of the system with dirt, water, and other foreign material.

11. Remove the reservoir cap.

12. Remove the reservoir diaphragm when checking or adding fluid.

13. Fill the reservoir with new clutch hydraulic fluid or an approved DOT 3 brake fluid. Note: Do not use fluid that has been bled from a system to fill the reservoir, as it may be contaminated. Never use transmission fluid, motor oil, power steering fluids or any mineral oil fluids to fill or lubricate the Clutch Hydraulic System.

14. Pump the clutch pedal 15-20 times making sure the pedal is allowed to return completely between strokes. Note: Check and fill the reservoir as needed while bleeding to prevent air from being drawn into the system.

15. Depress the clutch pedal and hold.

16. Slowly open the bleed screw located on the concentric slave cylinder and allow any trapped air to escape.

17. Close the bleed screw and release the clutch pedal. Do not over tighten the bleed screw.

18. Repeat Step 14 until all the air is pumped out of the concentric slave cylinder and clean, bubble free clutch fluid is visible in the reservoir. Note: During Step #14 the concentric slave cylinder will fill with clutch fluid and the release bearing will begin to move. Continued pedal strokes will bleed the system of all air and the release bearing will move through its entire stroke with each pedal application.

19. If clutch disengagement is not satisfactory, repeat the bleeding procedure. Under normal usage, small amounts of air will eventually work its way out of the system.

External Slave Cylinder - Removal and Installation

Prior to any vehicle service that requires removal of the slave cylinder, the master cylinder pushrod should be disconnected from the clutch pedal. If not disconnected, permanent damage to the slave cylinder will occur if the clutch pedal is depressed while the slave cylinder is disconnected from the transmission.

Some external slave cylinders do not have bleed screws. These cylinders must be filled with clutch hydraulic fluid before they are installed on the transmission. Refer to the Hydraulic Bleeding of External Slave Cylinders without Bleed Screws instructions for this operation.

All slave cylinders are shipped with a plastic pushrod-retaining strap. This strap retains the pushrod during shipping and also provides a nonmetallic end for the pushrod, which helps prevent wear and squeaks when the clutch is actuated. Make sure the pushrod-retaining strap is in place and secure when the slave cylinder is reinstalled to the vehicle. The pushrod retaining strap bands are designed to break during the first clutch application.

1. Using a 3mm (7/64”) diameter punch, drive out the retaining pin that holds the hydraulic tube to the master cylinder. Be careful not to damage the master cylinder body. Note: On some vehicles the hydraulic line will have an in-line tube connector that can be disconnected using the hydraulic line Quick Connect tool.

2. Remove the bolts or retainer holding the slave cylinder to the transmission.

3. Remove the slave cylinder from the transmission.

4. Install the new slave cylinder. Make sure the pushrod is securely seated in the cup end of the clutch release lever.

5. Install the slave cylinder retainer or attaching bolts and tighten per the vehicle manufacturer’s Shop Manual requirements.

6. Inspect the hydraulic tube coupling for damage and contamination, replace the “O” ring and lube with clutch fluid.

7. Insert the tube fitting into the slave cylinder fluid port and replace the retaining pin.
Be careful not to damage the slave cylinder body.

8. If applicable, reconnect the hydraulic tube by inserting the male coupling into the female coupling on the adjoining tube or slave cylinder. Make sure the coupling is secure.

9. Bleed the slave cylinder per the Hydraulic Bleeding instructions.

Clutch Hydraulic Tube – Removal and Installation

1. Before removing the hydraulic tube assembly from the vehicle, carefully inspect the tube and take note of the tubes routing. When reinstalling the new tube it must be routed exactly as the tube being replaced.

2. Using a 3mm (7?64”) diameter punch, drive out the pin that holds the hydraulic tube to the master cylinder and the slave cylinder body. Be careful not to damage the master cylinder or slave cylinder body. Note: On some vehicles the hydraulic line will have an in-line tube connector that can be disconnected using the hydraulic line Quick Connect tool.

3. Lubricate the two small quad seals with the clutch hydraulic fluid and install on the new tube fittings.

4. Reinstall the new tube assembly. Pay careful attention to the tube routing. Do not kink tube or allow the tube to be closer than 4 inches to any engine exhaust manifold.

5. Insert the tube fitting into the master cylinder fluid port and replace the retaining pin. Be careful not to damage the master cylinder body.

6. Insert tube fitting into slave cylinder fluid port and replace the retaining pin. Be careful not to damage the slave cylinder body.

7. Where applicable, reconnect the in-line tube connector.

8. Bleed the system per the applicable Hydraulic Bleeding Procedures.