Brake Fluid Replacement - most important,
yet most overlooked

I doubt that there is an automotive technician who disagrees.

The efficient operation of a vehicle's braking system is the most important consideration before setting the wheels of a motor vehicle in motion.

Just about everything that's on the new car market these days provides the motorist with more than enough power to get them off the mark and take them over that government revenue generating speed limit before they realise!

Now comes the hard part - how to stop that vehicle with the same degree of efficiency and control that the vehicle had when it was new.

The question simply relates to how efficient the braking system on the vehicle is when it's a little older, say about 12 months, and it has travelled some 30,000 kilometres.

Tthe most overlooked component of a vehicle braking system is the brake fluid.

Vehicle manufacturers and brake fluid manufacturers recommend that the brake fluid be changed periodically.

Despite these recommendations, brake fluid replacement can be one of the most difficult service requirements to be understood by the motorist.

How can you see the brake fluid no longer meets its design specifications?

Well, now there's a cost effective way by measuring the boiling point of the brake fluid with a Brake Fluid Safety Meter.

The vehicle owner often asks "Why change brake fluid?"

Brake fluid is hygroscopic.  In layman terms it attracts and absorbs water. This is unavoidable as it is part of brake fluid's chemistry and even though it is in a 'closed' system, the attraction for water is so strong that it is still absorbed. When brake fluid absorbs water, its boiling point is reduced.

A good quality fluid, having a boiling point of say 260 degrees C when new could, over two years, have its boiling point gradually reduced to about 160 degrees C.

This deterioration continues and eventually the heat produced by friction between the brake lining materials and discs or drums will vaporise the fluid. Vapour, unlike liquid, is compressible, so pressing the brake pedal merely compresses vapour instead of operating the brakes (this is known as the vapour lock point and it is slightly lower than boiling point).

This kind of brake failure can only be avoided by changing the brake fluid regularly.

How often should brake fluid be changed?

Unlike engine oil, which should be changed according to the distance driven, brake fluid deteriorates not with distance but with time. It continues to absorb water even when the vehicle is stationary. Most vehicle manufacturers recommend regular brake fluid changes on a time basis, e.g. every year or two.

Unfortunately, such recommendations are not always followed and independent surveys have shown that many vehicles have dangerous brake fluid in them.

Vehicle manufacturers also specify the brake fluid performance required usually by reference to a DOT specification, and brake fluid should therefore always be changed before it 'fails out' of specification. DOT specifications include minimum boiling point requirements and measurement of boiling point is one of the best ways to determine whether or not fluid needs changing.

The vehicle manufacturer usually specifies the required brake fluid performance levels. Specified Fluid minimum 'wet' Boiling Point:

DOT 3 140 Degrees C

DOT 4 155 Degrees C

SUPER DOT 4 180 Degrees C

DOT 5 180 Degrees C

Brake fluid should always be changed if its boiling point is below the minimum requirement, and a change of fluid is recommended if there is less that 10 per cent 'safety margin' left, e.g. if a vehicle requires a DOT 4 fluid and the Brake Fluid Safety Meter indicates a boiling point of less that 171 degrees C (155 degrees C plus 10 per cent) then the fluid should be changed.

Have your brake fluid changed at least every two years. This can be done inexpensively when carried out as part of your service.

. We flush the braking system and refill with manufacturer recommended brake fluid. Bleed air from system and adjust brakes and de-dust and adjust. (Includes up to 1 litre of Dot 4 Brake Fluid)

Note: Additional items found to require attention will be reported. The technician will provide a quote to do any additional work and will complete this at your request.