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Brake Fluid Flush Explained

Written by maryp posted on Wednesday, March 30th, 2011

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Why do I need Brake Fluid Flush?

And how do you know my fluid needs to be changed?

Let’s take a look at your Brake Fluid.

The First step is to access the BMW or MINI Brake Fluid reservoir (on some models you will remove the microfilter to get to the reservoir). The level of your Brake Fluid will be checked, and also a visual check for clarity. Next step is the test strip. This chemical reaction indicator will measure copper content of a sample of the fluid, (BTW, not everyone does that extra step).

If the copper exceeds 200 ppm it is suggested that your fluid be changed. The excess copper is indication that the fluid’s active properties are breaking down. The higher the copper content, the more your fluid has deteriorated. A few years ago, I believe it was Brembo who proved the deterioration of your Brake Fluid will diminish the performance properties of stopping your BMW or MINI when the brakes are applied.

Brake Fluid is a Hyrgoscopic (that’s what they call it) fluid which draws water out of the air naturally, absorbing moisture. Your Brake system is vented to the atmosphere because the fluid has to be allowed to expand and contract. Water in brake fluid is not good for the following reasons; when your you put your foot on the brake you are transferring kinetic energy into heat energy, and brake fluid is boiling at a high temp, which (if full of water) is turning into steam affecting your braking and the hydraulic system negatively.

The above scenario can give you spongy brake pedal feel or loss of braking power. Old brake fluid that contains a lot of water can be bad enough to result in complete loss of braking ability, (Dave experienced this himself and it is scary)! Excess water in the brake fluid can also corrode lines and the ABS pump of your BMW, (an expensive part which is about $1800). Excess water in the brake fluid can also result in corrosion of other braking components. There is a certain amount of condensation moisture that accumulates under normal conditions with that “boiling” action go on. Hint: Think of a pot of boiling water with a lid on it, (lots of water at the top of the lid).

Keep in mind that a Brake Fluid Flush recommendation by time can vary depending on the driving conditions, temperatures, weather, etc.. By using the test strips we are doing a chemical analysis of the fluid so there is NO guessing on when it is time to completely replace your Brake Fluid (not really a “flush”, but a complete drain and fill). We use the fluid recommended by BMW for both your beautiful BMW and your MINI, too. You will want to have your fluid changed out every 2 years at minimum.

Happy Motoring!

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