If the clutch/brake fluid is murky or muddy, or has not been changed within the last two years, flush the system and change the fluid. Flushing the old fluid from the clutch lines is done using a brake system pressure bleeder.
- Remove brake fluid reservoir cap. Using a clean syringe, remove brake fluid from reservoir. Refill reservoir with clean DOT 4 brake fluid.
- Cooper: remove battery box to gain access to slave cylinder on top of transmission.
- Cooper S: Raise car and remove splash shield to gain access to slave cylinder on front side of transmission
- Remove bolts holding slave cylinder to transmission.
- Compress slave cylinder – special tool available or home make one.
- Attach pressure brake bleeder to fluid reservoir and pump brake bleeder a few times to pressurise system.
- Do not exceed 1 bar (14psi) pressure
- Brake fluid is poisonous, highly corrosive and dangerous to the environment. Wear safety glasses and rubber gloves when working with brake fluid. Do not siphon brake fluid with your mouth. Immediately clean away any fluid spilled on painted surfaces and wash with water, as brake fluid will remove paint.
- Always use new brake fluid from a fresh, unopened container. Brake fluid will absorb moisture from the air. This can lead to corrosion problems in the clutch and brake hydraulic systems, and will also lower the brake fluid boiling point. Dispose of brake fluid properly.
- Connect a hose from clutch slave cylinder bleeder valve to a container.
- Open bleeder valve and allow brake fluid to expel until clean fluid comes out, free of air bubbles.
- Close bleeder valve and disconnect pressure bleeding equipment from fluid reservoir.
- Decompress slave cylinder and install back on transmission.
- Slowly operate clutch pedal about 10 times. Fill reservoir with clean fluid as necessary.
- Check clutch pedal free play. Repeat procedure if free play exceeds 7-10mm.