Brake fluid is hygroscopic — it absorbs water, corrodes cylinders and drops its boiling point. Renew every two years; do not mix DOT 4 and DOT 5 silicone.
Step by step
- 01
Protect the paint and gather kit
Cover paintwork around the master cylinder — brake fluid strips paint on contact. You need fresh fluid, a clear bleed hose, a jar, spanners, and a helper (or a one-man bleed kit).
- 02
Empty the old fluid from the reservoir
Syringe as much old fluid as possible out of the master cylinder reservoir. Refill with fresh fluid of the correct type. Never let the reservoir run dry during bleeding — you will suck in air.
- 03
Bleed in the correct order
Bleed the wheel furthest from the master cylinder first, then work back: typically nearside rear, offside rear, nearside front, offside front. Bleed each wheel until fluid runs clean and clear with no bubbles.
- 04
Keep the reservoir topped up
Check and top up the reservoir every couple of wheels — running it dry means starting over.
- 05
Firm pedal check
With everything closed, the pedal should be firm and hold under sustained pressure. A soft/spongy pedal means air is still in the system — repeat the bleed.
- 06
Dispose of old fluid
Old brake fluid is hazardous waste — take it to a recycling centre.
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This guide is a general introduction and is not a substitute for the official Workshop Manual for your car.