Brake fluid replacement

Why must brake fluid be replaced?

Brake fluid is hygroscopic — it absorbs moisture from the air, even through sealed reservoirs and lines. After 1–2 years moisture content can reach 3–4 %, significantly reducing the boiling point. When you brake hard and continuously, for example down a long descent with a trailer, the fluid can reach its boiling point and form vapour bubbles. Vapour is compressible while liquid isn't — the result is that the pedal sinks to the floor without the brakes biting. Worst case: total brake failure.

When should fluid be replaced?

Most car manufacturers specify a 2-year fluid change regardless of mileage. Some electrified models have stricter intervals (annual) and some Toyota/Lexus hybrids every 3 years. Always check your own vehicle's service book. At the periodic technical inspection (EU-kontroll) brake fluid boiling point is a check point — too low a boiling point can result in a defect note or rejection.

What we do at the workshop

First we test existing fluid with an electronic moisture meter or boiling-point tester. Then we connect vacuum equipment to the caliper bleed nipples (in the correct sequence: furthest from the master cylinder first) and drain the system fully. New fluid of correct specification (typically DOT4, but some cars require DOT5.1 or LV) is filled, and we bleed the system until only clean fluid comes out at each bleed point. On cars with ABS and ESP we run an ABS activation routine via diagnostic equipment to ensure the fluid inside the HCU module is also replaced.

Finally we test the pedal for firm pressure and run a short test drive to verify everything works.

Original or alternative fluids?

Brake fluid must always be the correct DOT class. DOT4 is most common in modern cars, while some high-performance and hybrid vehicles require DOT5.1 or LV specification (Low Viscosity, for cars with electronically controlled brakes). We use quality brands such as ATE, Bosch, Castrol or the manufacturer's own fluid — never the cheapest off-the-shelf product.

What about the warranty?

Replacement at an authorised workshop with correct-specification fluid does not affect the new-car warranty. We document everything in the service book. We give 12 months' guarantee on work and parts.

Book online easily or call us on 41 17 32 24.