The temperature of boiling is, perhaps, one of the main parameters of the brake fluid, as in the case of emergency braking liquid in the braking system heats up quickly. In the moment of boiling of a brake liquid it formed air bubbles, whereby the liquid loses the property of incompressibility. What happens when boiling "tomosuke"? The brake pedal is gently utaplivajutsja to the floor, and the reaction of the brake system the pedal will be extremely weak or absent.
In winter, a particularly relevant property of brake fluid is the temperature of its solidification. The fact is that in very cold weather the fluid becomes thick and hardens, plugging the lumen in pipes and hoses of the braking system. In the absence of the circulation of the brake fluid in the system the brake pedal becomes stiff, it is almost impossible to press. In this case, the brake system will remain faulty until then, until the fluid is thawed.
The degree of aggressiveness of a brake liquid will directly depend on the integrity of rubber-technical products, which is equipped with machine and anti-corrosion and lubricating properties "tomosuke" — the life of metal brake system parts.
The hygroscopicity value will indicate how much moisture absorbs the brake fluid in the process. Why is this parameter so important? The fact that gets wet boiling point of brake fluid rapidly decreases, and its operating properties deteriorate. The lower this value is, the longer will be its life.
the basic basics
A mixture of butyl alcohol with castor oil – this is the basis of brake fluids used in cars manufactured before 1985. Based liquid butyl alcohol is characterized by high lubricating properties and lack of aggressiveness towards rubber products. Temperature characteristics of the brake fluid, to put it mildly, do not impress: the temperature of its boiling point is about 1200 C and pour point equal to about -200 C.
Much better things with brake fluids based on glycol or polyglycol. Their boiling point reaches 2600 s, and the pour point increased to -400 C, is enough for everything for the climatic conditions in much of the former Soviet space. However, there they have a significant drawback – the high value of hygroscopicity. For a year of service so brake fluid absorbs moisture, which constitutes 2% of its volume and the same amount of water – for the second year of operation, after which binding needs to be replaced.
Another type of brake fluid is silicone-based. High (up to 3000 C) boiling point, a small indicator of compressibility and absolute negigroskopicny allocates it among others, but because of the rather high cost it is used only in sports cars.
Classification of brake fluids according to DOT
Most brake fluids are classified using the commonly used standard DOT (Department Of Transportation). It is with class definitions for DOT in most cases, and begins selection of fluid in buying it. The number after the abbreviation DOT means the class of admission.
DOT 3 – brake fluid based on glycol, having a boiling temperature of 2200 C to "dry" liquids and 1500 C – for wet, aggressive enough to paint. Service life – 2 years.
DOT 4 fluid for glycol based with the addition of a package of anti-corrosion and lubricating additives, the temperature of boiling "dry" and "wet" fluids is With 2400 and 1600 C, respectively. Can corrode the paint. Service life – 2 years.
4.5 DOT, DOT 4+ or SUPER DOT 4. DOT 4 having a higher boiling point 2600 C and 1800 C. the Other characteristics are identical to brake fluid DOT 4 class.
DOT 5 fluid is made of silicone. The boiling point is 2800 and 1800 (for "dry" and "wet" fluids). Neutral to lacquer coatings and negigroskopicny. Requires replacement every 5 years.
DOT 5.1 is modified and improved DOT 4.5, with operating temperatures of 2700 and 1800 C. the service Life is 1 year.Choosing a brake fluid for the car, be sure to follow the recommendations of the manufacturer of your vehicle.
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