Audi A4

since 1994 release

Repair and operation of the car

This liquid, yellowish, poisonous and aggressive in relation to an automobile varnish, does not corrode metal and rubber details. She remains rather zhidkotekuchy at –40 °C and, despite the zhidkotekuchest, about about 260 °C possess extremely high boiling point.

But brake fluid possesses very unpleasant property: it willingly absorbs water, it "is hygroscopic". Water, for example due to humidity of atmospheric air, can really get into brake fluid: through a broad tank or through microscopic not tight sites in brake hoses or in rubber cuffs. Such absorption of water leads not only to corrosion of metal details of brake system, but also causes fast decrease of a boiling point of brake fluid. At the content of water in only 2,5% its boiling point is only at 150 °C. Near the warmed brakes vials of steam in hydraulic liquid can be formed. They contract – the pedal of a brake can deeply fail, sometimes the foot presses simply in emptiness! In this case fast pumping of liquid a brake pedal sometimes helps. This effect is especially dangerous at a car stop after strong load of brakes. Because of a lack of a head wind everything, being in an environment of brakes, is warmed even more strongly. And approximately only in half an hour temperature of brake fluid goes down to the normal.

Therefore the plan of maintenance orders preventive replacement of brake fluid every two years. Brake fluid has to meet the FMVSS 116 DOT 4 specification. All liquids with such designation it is possible without fear to mix.