Brake fluid (Opel Frontera B)

Brake fluid is a mixture of glycol, polyglycol ether and several other components. This liquid is yellowish in color, very toxic and aggressive for the car's paintwork, however, it does not destroy metal and rubber parts and elements. The operating range in which the liquid retains its properties extends from -40°C to 260°C.

The disadvantages include the fact that brake fluid is hygroscopic, that is, it absorbs moisture from the air, and therefore it is not recommended to use fluid stored for a long time in an open container. Moisture can also enter the brake fluid in the brake system, for example from the air through the reservoir or through microscopic leaks in the brake lines and hoses. Such absorption of moisture not only leads to corrosion of metal parts of the brake system, but also significantly lowers its boiling point. Even with a water content of 2.5%, the brake fluid boils at approximately 150°C. This is especially dangerous during heavy braking, as the brakes can become very hot and steam bubbles can form in the brake fluid near the hot brakes. The bubbles are compressed, causing the brake pedal to travel longer and, in some cases, the pedal may even sink. In this case, quickly pumping up the pressure with the brake pedal may help.

This effect is especially dangerous after intensive braking when stopping the car, since due to the lack of oncoming air flow, the brake mechanisms heat up even more and this highest temperature remains for another 15 minutes of parking. In this case, the brake fluid only reaches its normal temperature after 30 minutes. Therefore, to avoid such an effect, the maintenance regulations require replacing the brake fluid every year. Brake fluid must meet the safety standards of FMVSS §571.116 DOT 4 and also the SAE specification J1703. All fluids that meet these specifications are miscible.