Clutch: Replace Master Cylinder

The master cylinder is a hydraulic control device that converts physical pressure (commonly from a driver's foot) into hydraulic pressure to operate other device(s) in the hydraulic system. The most common automotive uses of master cylinders are in brake and clutch systems. The operated device in the clutch system is called the slave cylinder. In brake systems, the operated devices are brake calipers and/or wheel cylinders.

How a master cylinder works

A master cylinder is made up of a reservoirs of fluid, a pistons, and a hardened line. When the clutch pedal is depressed, the piston moves in to create pressure in the reservoir. This pressure compresses the fluid through the line to activate the slave cylinder. The increased pressure in the slave cylinder activates the seconday piston, depressing the clutch.

Tools needed to perform removal

• 10mm wrench (and socket)
• 12mm socket
• 10mm flare nut crows foot (MUST HAVE)
• Socket wrench
• 6" socket extension
• Pliers (needle nose or standard)
• Dot 3 or 4 Brake fluid
• Paper towels for cleanup
• Flash-light
• Replacement master cylinder or rebuild kit (typically available from AutoZone - $57)

Steps to remove N/A master cylinder

Replacing the master cylinder in the N/A can be a simple process that should typically take no longer than 30-45 minutes. Limited/Low mechanical skill is required to complete this project. Take care when loosening the nut on the hardline on the clutch master cylinder or this will turn into a much bigger project if you strip it.

• Locate the master cylinder in the engine bay. It is mounted to the firewall on the driver's side. It's small reservoir is co-located with the much larger brake booster.

• Drain fluid out of the master cylinder reservoir
  • This can be done by loosening the bleeder on the slave cylinder a quarter turn then pumping the clutch a few times. You can use a piece of 3/8 hose from the bleeder to an oil change pan to reduce the mess.
    • Tip: On the SOHC engines you can reach the clutch slave cylinder bleeder with a long set of extensions (~1.5 ft) without removing anything else if you're crafty.
  • Don't forget to tighten this back up until you're ready to bleed the system (don't over-torque the bleeder!).

• With a 10mm wrench, loosen the bolt securing the reservoir to the cylinder until the reservoir can be removed.

• Using the 10mm crows foot attached to the 6" socket extension to remove the hardline going in to the master cylinder.

NOTE: Be extremely careful not to crimp this line!!

• Push the drivers seat back and recline it as far as possible. It is easiest to work if you are on your back under the dash.

• Attached to the clutch pedal will be a bracket that secures it to the master cylinder rod that can be seen protruding from the firewall.

• With the 10mm wrench, loosen the nut on the master cylinder rod on the firewall side of the bracket.

• Pull the security pin out of the bolt attaching the master cylinder rod to the clutch pedal bracket.

• Move the bracket/rod assembly aside and turn the bracket counter-clockwise until it is removed.

• Using the 12mm socket undo the bolts above and below the portion of the master cylinder protruding through the firewall.

• From outside the car, the master cylinder can be simply removed after some manipulation.

• The reinstallation process is simple and an exact reverse of these directions.

• Once reassembled, bleed the clutch system to remove any remaining air from the lines and components.