Clutch: Replace Master Cylinder

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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 crows foot (MUST HAVE)
  • Socket wrench
  • 6" socket extension
  • Pliers (needle nose or standard)
  • Dot 3 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 is a simple process that should typically take no longer than 30-45 minutes. Limited/Low mechanical skill is required to complete this project.

  • 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 (if applicable)
  • 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.
This article originated from a thread or post on 3000GT/Stealth International. (1884)