A clutch master cylinder is a part of the clutch system that provides leverage assistance to the operator. The clutch master cylinder operates just like the master cylinder of a brake system. A clutch master cylinder contains a reservoir that stores brake fluid, only dot 3 type. The cylinder is connected to the clutch slave cylinder located on the transmission through hoses.
When you push the clutch pedal, brake fluid flows from the clutch master cylinder to the slave cylinder, applying the pressure necessary to engage the clutch. When you release the clutch pedal, a return spring located on the slave cylinder will force the brake fluid back to the clutch master cylinder.
Part 1 of 10 : Know the signs of failure
There are three different ways to determine if the clutch master cylinder is failing or has failed. The main chamber seal in the back of the clutch master cylinder will split and leak out brake fluid causing the reservoir to become low. As the pedal is pushed down the piston cup inside the cylinder housing will create a suction and draw in air causing a loss of pressure.
The reservoir bushing will become dry and cracked causing the brake fluid to drain out. When the brake fluid is too low in the reservoir and the bushing has cracks, air will draw in and cause a loss of pressure.
The piston cup seal spits inside the clutch master cylinder causing the brake fluid to move back and forth. This eliminates the fluid travel to the slave cylinder causing a loss of application.
Pascal’s law states that all areas that have confined fluid in them are not compressible and all pressure is equal in every location. The application of a larger dimension will have more leverage than a smaller dimension.
Pascal’s law plays a large role in the clutch hydraulic system. As long as the system has fluid at the proper level, applied force, and all of the air bled out, then the clutch hydraulic system will work correctly.
However, when air is induced into the system the air becomes compressible allowing the fluid to create a standstill. If the fluid is low or if the applied force is minimal, then the force will be low causing the slave cylinder to operate at about half way. This will cause the clutch to slip and not engage any gears and the clutch will not release properly.
Part 2 of 10: Verifying the clutch master cylinder condition
Step 1: Open your hood up. Look at the firewall of the vehicle and locate where the brake master cylinder is.
The clutch master cylinder will be right next to it.
Step 2: Visually look at the clutch master cylinder for any leaking brake fluid. If brake fluid is present, pop or unscrew the reservoir cap and check the fluid level.
If the level is at the top of the reservoir, then the clutch hydraulic system was over full. If the reservoir was low, then there was an external leak in the clutch hydraulic system.
Step 3: Check the mounting hardware for the clutch master cylinder. Visually see if all locking nuts are present.
Try to move the clutch master cylinder by hand. It should be hard and not able to move.
Part 3 of 10: Preparing the vehicle
Materials Needed
Step 1: Park your vehicle on a flat, hard surface. Make sure that the transmission is in park (for automatics) or in 1st gear (for manuals).
- Note: This is only for vehicles with all wheel drive transmissions or rear wheel drive transmissions.
Step 2: Place wheel chocks around the rear tires. These will be remaining on the ground.
Engage the parking brake to the lock the rear tires from moving.
Step 3: Raise the vehicle. Using a floor jack, lift under the vehicle at its specified jacking points until the wheels are completely off the ground.
Step 4: Place the jack stands. The jack stands should go under the jacking point locations then lower the vehicle onto the jack stands.
For most modern cars, the jacking points for jack stands will be on the pinch weld just under the doors along the bottom of the car.
Part 4 of 10: Removing the integrated clutch master cylinder
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
- Vampire pump and bottle
Step 1: Grab your vampire pump with a bottle. Remove the reservoir cap from the cylinder’s reservoir.
Use the vampire pump and retrieve all of the brake fluid from the reservoir. When done removing all brake fluid, put the reservoir cap back on.
- Warning: Do not get brake fluid on any paint. This will cause the paint to peel and chip away.
Step 2: Remove the hydraulic line from the clutch master cylinder. Be sure to put a plastic bag on the end of the line with the rubber band to keep brake fluid from leaking.
- Note: Do not bend the hydraulic line as it may crack or break.
Step 3: Remove the cotter pin. Go in the driver’s compartment of the vehicle and remove the cotter pin from the anchor pin.
This will be found on the clevis attached to the clutch master cylinder push rod with a pair of needle nose plyers.
Step 4: Remove the anchor pin from the clevis of the push rod.
Step 5: Remove the mounting nuts from the clutch master cylinder.
Step 6: Remove the clutch master cylinder from the firewall. Be sure to keep the cable mounting side facing up to prevent dripping of brake fluid.
Place the clutch master cylinder in a bag.
Part 5 of 10: Removing the the clutch hydraulic system assembly
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Drip pan
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
- Vampire pump
Step 1: Remove all brake fluid. Remove the reservoir cap from the cylinder’s reservoir.
Use the vampire pump and retrieve all of the brake fluid from the reservoir. When done removing all brake fluid, put the reservoir cap back on.
- Warning: Do not get brake fluid on any paint. This will cause the paint to peel and chip away.
Step 2: Remove the cotter pin. Go in the driver’s compartment of the vehicle and remove the cotter pin from the anchor pin on the clevis.
This will be attached to the clutch master cylinder push rod with a pair of needle nose plyers.
Step 3: Remove the anchor pin from the clevis of the push rod.
Step 4: Remove the mounting nuts from the clutch master cylinder.
Step 5: Locate the hydraulic line linking clutch master cylinder to the slave cylinder. Remove all mounting insulated clamps that mount the hydraulic line to the vehicle.
Step 6: Grab your creeper and go under the vehicle. Remove the two bolts or clamp that secures the slave cylinder to the transmission.
Step 7: Remove the entire system. Very carefully, remove the entire system (clutch master cylinder, hydraulic line, and slave cylinder) up through the engine compartment.
- Warning: Do not bend the hydraulic line for it will break.
Part 6 of 10: Prepare the integrated clutch master cylinder
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
Step 1: Remove the clutch master cylinder from its package. Visually check to see if there are any damages to the cylinder.
Make sure that the seal is in the back of the cylinder housing.
Step 2: Take the master clutch cylinder and put it into a vise. Clamp down until the cylinder will not move.
Step 3: Install the hydraulic line for the tube. Install the tube into the hole where the hydraulic line would thread into.
Remove the reservoir cap and place the tub into the reservoir.
Step 4: Fill the reservoir up with brake fluid. Leave 1/4 inch from the top empty.
Step 5: Use the brass punch as an extension to prime the cylinder. Slowly pump the cylinder from the back of the clutch master cylinder.
Watch for the brake fluid to go from the clear tube to the reservoir. This primes the cylinder and removes all of the air inside the cylinder.
Part 7 of 10: Prepare the clutch hydraulic system assembly
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
Step 1: Remove the clutch master cylinder from its package. Visually check to see if there are any damages to the cylinder.
Make sure that the seal is in the back of the cylinder housing.
Step 2: Put the clutch master cylinder and slave cylinder assemble into a vise. Clamp down until the clutch master cylinder will not move.
Place the slave cylinder on a stool or something to support it.
Step 3: Remove the bleeder screw. Place a drip pan underneath the slave cylinder and remove the bleeder screw.
Step 4: Fill the reservoir up with brake fluid. Leave 1/4 inch from the top empty.
Step 5: Use the brass punch as an extension to prime the cylinder. Slowly pump the cylinder from the back of the clutch master cylinder.
Watch for the brake fluid to drip out of the slave cylinder. You will have to fill the reservoir about three times to fill the entire system. This primes the cylinder and removes most of the air inside the cylinder, hydraulic line, and slave cylinder.
When there is a solid stream of brake fluid coming out of the bleeder hole on the slave cylinder, stop and install the bleeder screw.
Step 6: Get a helper. Have the helper use the brass punch and pump the cylinder.
You then would need to loosen the bleeder screw to allow air to escape as brake fluid runs out.
- Note: You may need to loosen the bleeder screw up a few times during pumping cycles to remove all air in the hydraulic system.
Step 7: Make sure that the bleeder screw is tight. Fill up the reservoir with brake fluid to the fill line and install the reservoir cap.
Part 8 of 10: Installing the integrated clutch master cylinder
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Drip pan
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
Step 1: Install the clutch master cylinder into the firewall. Be sure to keep the clear tube on to prevent dripping of brake fluid.
Step 2: Install the mounting nuts. Go in the driver’s compartment of the vehicle and install the mounting nuts onto the clutch master cylinder.
Torque them down to the specifications that will be given in the package. If there is no instructions, then tighten the bolts by hand then an 1/8 turn.
Step 3: Install the anchor pin. Install it into the clevis of the push rod.
- Note: Do not push on the clutch pedal. The force can cause the clear tube to come out of the clutch master cylinder and begin to leak brake fluid out.
Step 4: Install a new cotter pin. It should be installed in the anchor pin on the clevis attached to the clutch master cylinder push rod with a pair of needle nose pliers.
-
Warning: Do not use the old cotter pin due to work harden and fatigue. The old cotter pin could break prematurely.
Step 5: Get your drip pan and place it under the clutch master cylinder. Remove the clear tube and install the clutch hydraulic line.
- Warning: Do not cross thread the hydraulic line as you install it. Brake fluid will leak out.
Step 6: Bleed the hydraulic line to cylinder. Have a helper press the clutch pedal and hold it. Loosen the line up and let the air out of the system.
You may need to perform the bleeding procedure a couple more time to remove all air. Tighten up the line tight.
Step 7: Remove the reservoir cap. Top brake fluid off to the full line.
Part 9 of 10: Installing the clutch hydraulic system assembly
Materials Needed
- Allen wrench set
- Boxed end wrenches
- Brass punch
- Breaker bar
- Drip pan
- Fastener remove
- Ratchet with metric and standard sockets
- Needle nose pliers
- Torques bit set
- Torque wrench
- Vampire pump and bottle
Step 1: Install the entire system. Very carefully, install the entire system (clutch master cylinder, hydraulic line, slave cylinder) down through the engine compartment.
- Warning: Do not bend the hydraulic line since it will break.
Step 2: Install the slave cylinder. Go underneath the vehicle and install the slave cylinder by screwing in the bolts finger tight then 1/8 turn to tighten the clamp.
Step 3: Install the clutch master cylinder into the firewall.
Step 4: Install the mounting nuts. Go in the driver’s compartment of the vehicle and install the mounting nuts onto the clutch master cylinder.
Torque them down to the specifications that will be given in the package. If there is no instructions, then tighten the bolts by hand then an 1/8 turn.
Step 5: Install the anchor pin into the clevis of the push rod.
Step 6: Install a new cotter pin. Do this in the anchor pin on the clevis attached to the clutch master cylinder push rod with a pair of needle nose plyers.
- Warning: Do not use the old cotter pin due to work harden and fatigue. The old cotter pin could break prematurely.
Step 7: Install all mounting insulated clamps. Go back to the engine compartment and install all mounting insulated clamps that mount the hydraulic line to the vehicle.
- Note: Keep in mind, the clutch hydraulic system assembly is already primed and full of fluid with all of the air out of the system.
Step 8: Raise the vehicle. Lift under the vehicle at its specified jacking points until the wheels are completely off the ground.
Step 9: Remove the jack stands. Move them far away from the vehicle.
Step 10: Lower the vehicle to where all four wheels are on the ground. Pull out the jack and put it aside.
Step 11: Remove the wheel chocks from the rear wheels. Put them aside.
Part 10 of 10: Testing the new clutch master cylinder
Step 1: Make sure that the transmission is in neutral. Turn on the ignition key and start the engine.
Step 2: Press down on the clutch pedal. Move the gear shifter to a selection of your choice.
The shifter should slide easily into the gear selected. Shut the engine off when you are done with the test.
Step 3: Test drive the vehicle. Drive the vehicle around the block.
- Note: During the test drive change gears from first gear to the top gear one at a time.
Step 4: Press the clutch pedal down. Do this when moving from the selected gear to neutral.
Step 5: Press the clutch pedal down. Do this when moving from the neutral position to another gear selection.
This is process is called double clutching. This insures that the transmission has little to no power from the engine with the clutch disengaged properly. The process is to prevent clutch damage and transmission gear damage.
If you do not hear any grinding and the shifting feels smooth from one gear to another, then the clutch master cylinder has been fixed correctly.
If you cannot engage the transmission into any gear without grinding or if the clutch pedal will not move, then there may be further diagnosis of the clutch pedal assembly or a possible transmission failure. If the problem persists, then you should seek out help from one of our certified mechanic that can inspect the clutch and transmission and diagnosis the problem.
