How to replace the clutch slave cylinder

Clutch slave cylinders must be replaced if brake fluid leaks. If the gears are grinding or the clutch won't engage, the clutch pedal may be at fault.

The clutch slave cylinder is the part of the clutch system that assists the clutch fork. The clutch slave cylinder works in the same way as the hydraulic cylinder on the boom lift. The cylinder is connected to the clutch master cylinder, located on the firewall next to the brake master cylinder, through a hose.

When you depress the clutch pedal, brake fluid flows from the clutch master cylinder into the slave cylinder, applying the pressure needed to engage the clutch. When you release the clutch pedal, a return spring located on or inside the slave cylinder directs the brake fluid back to the clutch master cylinder.

Part 1 of 8. Know the Signs of Failure

There are two different ways to determine if the clutch master cylinder is bad. The master chamber seal in the middle of the clutch slave cylinder will crack and leak brake fluid, causing the reservoir in the clutch master cylinder to become low.

When the pedal is depressed, the piston inside the cylinder body causes the brake fluid to slosh out with great force through the seal. When the brake pedal is released, the tension of the return spring pulls the piston back into its housing, causing air to be drawn into the slave cylinder.

The return spring breaks or weakens, then the push rod of the working cylinder remains pressed with full force to the clutch fork. The clutch pedal will press into the floor, but will not return when the clutch pedal is released.

Pascal's law states that all areas containing fluid are incompressible and all pressures are the same anywhere. Applying a larger dimension will have more leverage than a smaller dimension.

Pascal's law plays a big role in the hydraulic clutch system. As long as there is fluid at the proper level in the system, force is applied and all air is bled, then the hydraulic clutch system will work properly. However, when air is forced into the system, the air becomes compressible, allowing the fluid to stop.

If there is little fluid, or if the applied force is minimal, then the force will be low, causing the slave cylinder to operate about half way. This will cause the clutch to slip and not engage any gears as the clutch will not disengage properly.

Part 2 of 8: Preparing for the job of replacing the clutch master cylinder

Necessary materials

• Flash
• Jack
• Jack stands

Step 1: Park your vehicle on a level, firm surface.. Make sure the transmission is in park (for automatic transmission) or 1st gear (for manual transmission).

• Attention: Only for vehicles with AWD or RWD transmission.

Step 2: Install wheel chocks around the rear wheels.. Apply the parking brake to block the rear wheels from moving.

Step 3: Raise the car. Jack up the vehicle at the indicated points until the wheels are completely off the ground.

Step 4: Install Jacks. The jack legs must pass under the jacking point. Then lower the car onto the jack stands.

For most modern cars, the jack stand attachment points are on a weld right under the doors along the bottom of the car.

• Attention: It is best to follow the vehicle owner's manual to determine the correct location for the jack.

Part 3 of 8: Checking the Condition of the Clutch Slave Cylinder

Required material

• flashlight

Step 1: Grab the creeper and get under the car.. Using a flashlight, inspect the clutch slave cylinder for damage and leaks.

If you can't see the fluid coming out, pull back the dust cover. Be sure to place a pan under the slave cylinder so that the brake fluid does not leak out.

Step 2: Open the hood of your car. Locate the clutch master cylinder and remove the reservoir cap.

Check if there is brake fluid in the reservoir.

Part 4 of 8: Removing the Clutch Slave Cylinder

Necessary materials

• Hex key set
• socket wrenches
• brass punch
• Switch
• Drip tray
• Fastener remover
• Pliers with needles
• Ratchet with metric and standard sockets
• Wrench
• Torque bit set
• Vampire pump and bottle

Step 1: Get a Vampire Pump with a Bottle. Remove the reservoir cap from the clutch master cylinder reservoir.

Use the vampire pump and collect all the brake fluid from the reservoir. After removing all the brake fluid, close the reservoir cap.

• A warning: Do not allow brake fluid to come into contact with the paint. This will cause the paint to peel and flake off.

Step 2: Get your tools and get under the car.. Remove the hydraulic line from the clutch slave cylinder.

Be sure to put a plastic bag on the end of the line with a rubber band so that brake fluid does not leak out of the line.

• Attention: Do not bend the hydraulic line as it may crack or break.

Step 3: Remove the bolts. Remove the two bolts or clamp that secure the slave cylinder to the gearbox.

Part 4 of 8: Removing the hydraulic clutch assembly

Necessary materials

• Hex key set
• socket wrenches
• brass punch
• Switch
• Drip tray
• Clasp remove
• Pliers with needles
• Ratchet with metric and standard sockets
• Wrench
• Torque bit set
• Vampire pump and bottle

Step 1: Get a Vampire Pump with a Bottle. Remove the reservoir cap from the cylinder reservoir.

Use the vampire pump and collect all the brake fluid from the reservoir. After removing all the brake fluid, close the reservoir cap.

• A warning: Do not allow brake fluid to come into contact with the paint. This will cause the paint to peel and flake off.

Step 2: Remove the cotter pin. Enter the driver's cab and remove the cotter pin from the anchor pin on the bracket.

It will be attached to the clutch master cylinder push rod with a pair of needle nose pliers.

Step 3: Remove the anchor pin. Remove it from the pusher fork.

Step 4: Remove the fixing nuts. Remove them from the clutch master cylinder.

Step 5: Find the hydraulic line. It connects the clutch master cylinder to the slave cylinder.

Remove all mounting insulated clamps that secure the hydraulic line to the vehicle.

Step 6: Grab the creeper and get under the car.. Remove the two bolts or clamp that secure the slave cylinder to the gearbox.

Step 7: Remove the entire system. Very carefully remove the entire system (clutch master cylinder, hydraulic line and slave cylinder) through the engine compartment.

• A warning: Do not bend the hydraulic line, otherwise it will break.

Part 5 of 8: Prepare the Slave Cylinder and Hydraulic System Assembly.

Necessary materials

• Hex key set
• socket wrenches
• brass punch
• Switch
• Drip tray
• Clasp remove
• Pliers with needles
• Ratchet with metric and standard sockets
• Wrench
• Torque bit set
• Vampire pump and bottle

Step 1: Prepare the clutch slave cylinder.. Remove the clutch slave cylinder from the packaging.

Visually inspect the cylinder and boot for damage. You may need to install a recoil spring, push rod and boot.

Step 2: Prepare hydraulic clutch assembly.. Remove the clutch master cylinder and slave cylinder assembly from the packaging.

Visually inspect the cylinder for damage. Make sure the seal is at the back of the clutch master cylinder housing.

Step 3: Take the clutch master cylinder and place it in a vise.. Clamp until the cylinder stops moving.

Place the slave cylinder on a stool or other support.

Step 4: Remove the bleed screw. Place a pan under the slave cylinder and remove the air bleed screw.

Step 5: Fill the reservoir with brake fluid.. Leave 1/4 inch at the top empty.

Step 6: Use a brass punch as an extension to fill the cylinder.. Slowly bleed the cylinder from the back of the clutch master cylinder.

Make sure that brake fluid does not leak from the slave cylinder. You will have to fill the reservoir approximately three times to fill the entire system. This fills the cylinder and removes most of the air from the cylinder, hydraulic line, and slave cylinder.

When a continuous stream of brake fluid flows out of the bleed hole on the slave cylinder, stop and install the bleed screw.

Step 7: Hire a Helper. Have an assistant use a brass punch and pump up the cylinder.

You will then need to loosen the air bleed screw so the air can escape as the brake fluid flows out.

• Attention: You may need to loosen the bleed screw several times during pumping cycles to remove all air from the hydraulic system.

Step 8: Make sure the bleeder screw is tight. Fill the reservoir with brake fluid up to the fill line and install the reservoir cap.

Part 6 of 8: Installing a New Clutch Slave Cylinder

Necessary materials

• Hex key set
• socket wrenches
• brass punch
• Switch
• Drip tray
• Fastener remover
• Pliers with needles
• Ratchet with metric and standard sockets
• Wrench
• Torque bit set
• Vampire pump and bottle
• Wheel chocks

Step 1: Grab the creeper and get under the car.. Install the clutch slave cylinder to the transmission support.

Tighten the bolts by hand and then tighten them 1/8 turn. If there was a clamp on the slave cylinder, install the clamp and make sure it is tight.

Step 2: Take a pallet and place it under the slave cylinder.. Remove the plastic bag from the clutch hydraulic line.

Install the clutch hydraulic line to the slave cylinder.

• A warning: Do not cross the hydraulic line when installing it. Brake fluid will leak out.

Step 3: Bleed the hydraulic line to the slave cylinder.. Have an assistant press and hold the clutch pedal.

Unscrew the bleed screw and bleed air from the system. Tighten the bleed screw and have an assistant release the clutch pedal.

You may need to perform the bleeding procedure a couple more times to remove all the air. Tighten the bleed screw firmly.

• AttentionA: If not all of the air comes out, you need to bleed the air from the line connected to the clutch master cylinder. Follow the same procedures as with the slave cylinder bleed screw.

Step 4: Add Brake Fluid. Remove the reservoir cap and add brake fluid to the full mark.

Part 7 of 8: Installing the hydraulic clutch assembly

Step 1: Install the whole system. Very carefully install the entire system (clutch master cylinder, hydraulic line and slave cylinder) down through the engine compartment.

• A warning: Do not bend the hydraulic line as it will break.

Step 2: Install the Slave Cylinder. Go under the vehicle and install the slave cylinder by hand-tightening the bolts plus 1/8 turn or by installing a clamp.

Step 3: Install the clutch master cylinder into the firewall..

Step 4: Install Mounting Nuts. Get into the cab of the car and install the mounting nuts on the clutch master cylinder.

Tighten them according to the specifications on the package. If no instructions are available, tighten the bolts by hand plus 1/8 turn.

Step 5: Install the anchor pin into the pusher bracket..

Step 6: Install the new cotter pin. Install it into the anchor pin on the bracket attached to the clutch master cylinder pushrod using a pair of needle nose pliers.

• A warning: Do not use the old cotter pin due to hardening and fatigue. An old cotter pin may break prematurely.

Step 7: Install Insulated Mounting Clamps. Return to the engine bay and install all of the insulated mounting clamps that secure the hydraulic line to the vehicle.

• Attention: Be aware that the hydraulic clutch system assembly is already primed and filled with fluid and all air has been purged from the system.

Step 8: Raise the car. Jack up the vehicle at the indicated points until the wheels are completely off the ground.

Step 9: Remove Jack Stands. Keep them away from the car.

Step 10: Lower the car so that all four wheels are on the ground.. Pull out the jack and set it aside.

Step 11: Remove wheel chocks from rear wheels.. Set them aside.

Part 8 of 8: Checking the New Clutch Slave Cylinder

Step 1: Make sure the transmission is in neutral.. Turn on the ignition key and start the engine.

Step 2: Press the clutch pedal. Move the gear selector to the option of your choice.

The switch should easily enter the selected gear. Turn off the engine when you are done with the test.

Step 3: Drive the car around the block. During the test drive, shift gears alternately from first to higher gear.

Step 4: Press the clutch pedal down. Do this when shifting from the selected gear to neutral.

Step 5: Press the Clutch Pedal Again. Do this when moving from neutral to another gear selection.

This process is called double clutching. This ensures that the transmission draws little to no power from the engine when the clutch is properly disengaged. This process is designed to prevent clutch damage and transmission damage. If you don't hear any grinding noise and shifting from one gear to another feels smooth, then the clutch master cylinder is installed correctly.

If you cannot engage the transmission in any gear without a grinding noise, or if the clutch pedal does not move, this may indicate an additional diagnosis of the clutch pedal assembly or a possible transmission failure. If the problem persists, you should seek the assistance of one of our certified mechanics who can inspect the clutch and transmission and diagnose the problem.