Brake Fluid Testing

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Brake Fluid Testing:

Brake fluid is designed to have a high boiling point, to withstand the high temperatures generated during braking. It has one major drawback – due to its chemical composition it absorbs moisture. This can be moisture from the air (via the breather hole in the master cylinder cap) or via the rubber hosing.

The more moisture in the brake fluid, the lower the boiling point. This increases the risk of "brake fade"; under heavy driving conditions, such as towing, or on steep, winding roads or stop-start braking at high speeds, brake fluid boils, turns to vapour, and the brake pedal goes straight to the floor with no braking action. This is known as "vapour-lock". If the police are called to such an accident, unless they test the boiling point of the brake fluid, all will appear normal: the brake fluid will have cooled back down, the brake pedal will feel firm, and the driver, having previously been unable to stop, will be faced with some serious questions.

Brake fluid is a safety-critical item, but how many drivers know or ever ask to get their brake fluid checked? They know about their oil & windscreen washer fluid, but brake fluid has been largely ignored by both the vehicle manufacturers & garages.

So how do you test for moisture in brake fluid? The only approved way is to boil it.

On the back of every bottle of brake fluid is a chart showing the "dry” (uncontaminated), and "wet” (contaminated) boiling points of all the various grades of brake fluid. Brake fluid manufacturers use what’s called an ERBP (Equilibrium Reflux Boiling Point) test to determine the boiling point of brake fluid. In a lab this can take hours to set up & complete.

The Alba tester is designed to test the boiling point of the fluid in the car in less than 30 seconds with digital accuracy. It works on all grades of brake fluid & shows clearly what the fluid has boiled at, and what the DOT minimums are for each, making the fluid change decision easy for the technician & the customer.

Once the brake fluid has been changed, the garage can offer to re-test the brake fluid using the Alba tester, to clearly show the improved results on the new fluid. Consumers should also be aware that new brake fluid from a sealed bottle must be used for every brake change. There have been cases where brake fluid has been left in an opened bottle, effectively making the "new” fluid as contaminated as the old.

It is hoped that at some time in the not too distant future, brake fluid testing will become part of the annual MOT test. As a safety-critical item, it’s surprising that it remains largely ignored by the regulatory authorities.

Alba Diagnostics Ltd

Tel: 01592 774333

Fax 01592 774777


The current written standards for brake fluid are as follows:
SAE J1703 (SAE=Society of Automotive Engineers)
ISO 4295
FMVSS no 116 (FMVSS=Federal Motor Vehicle Safety Standards)

The above are the standards shown on the back of brake fluid bottles & to which all brake fluids are tester. They all state brake fluid must be tested by the boiling point method. No other method is used or approved.

It follows therefore that conductivity meters are NOT considered appropriate or approved for brake fluid testing - or checking.



Click image above to download article, published in Auto-Torque Magazine, Autmn 2014


Click image above to download article, written by Hemal Mistry & published in CAT Magazine, Aug 2014



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