How to Change a Clutch Master Cylinder

by Don Bowman

The master cylinder for the clutch works very similar to the brake master cylinder. It uses Dot 111 brake fluid. Some of the clutch master cylinders have a reservoir on the master, and some are closed with a remote reservoir that is always located close to the master cylinder. They are all bolted to the firewall and have a rod that runs through the firewall and attaches to the brake pedal.

Raise the hood of the vehicle. Attach the vise grips to the remote reservoir hose close to the master cylinder (if there is one). Make it just tight enough to compress the hose so that it will not leak. Remove the hose from the master cylinder to the reservoir. Use the common screwdriver to loosen the clamp.

Place the drain pan under the master cylinder to catch the brake fluid. Brake fluid is not good for paint, so clean up any leaks with a cloth. Using a wrench, remove the hydraulic line from the master to the slave cylinder. On some cars the hydraulic line is not screwed on with a cap. It uses a plastic line that has a small O-ring on the end and is inserted into the master cylinder and held in with a roll pin. If this is the case, the plastic line will have a round, flat land on the end that is in the master cylinder and has an O-ring above the land. Use the center punch and small hammer to tap the roll pin out very gently. Once the pin is out, pull the plastic line out and watch for the small O-ring on the end of the line; do not loosen this.

Remove the master cylinder's push rod from under the dash. Look up from under the dash and locate a rod coming from the master cylinder where it comes through the firewall to the top of the clutch arm. The rod is attached to the top of the clutch arm with the use of a drift pin that travels through a hole in the flat part of the rod, then through the clutch arm. A spring clip keeps the pin from coming out. Use the needle-nose pliers to pull the spring clip out of the end of the drift pin and push the drift pin out of the hole. This will release the rod from the clutch arm.

Remove the two nuts on the engine side of the firewall that are holding the clutch master cylinder to the firewall. Pull the master cylinder straight out toward the front of the vehicle; it and the rod will come off.

Install the new master cylinder in reverse order of removal, leaving the hydraulic line off.

Fill the master cylinder with brake fluid. Bleeding the master cylinder will require a helper. Hold a finger over the hole for the hydraulic line so it does not leak. Have the helper push the clutch pedal all the way to the floor and hold it there. As the helper pushes the clutch pedal down, remove the finger from over the hole for the hydraulic line. As soon as the pedal is on the floor, place the finger back over the hole. Allow the helper to let the pedal back up again. Repeat this process until steady fluid is coming out of the master cylinder (no air). Once this is done, replace the hydraulic line.

Items you will need

About the Author

Don Bowman has been writing for various websites and several online magazines since 2008. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam).