GENERAL INFORMATION

When you press the brake pedal, the force is transferred by means of a hydraulic drive to the wheel (working) brake mechanisms, which stop the car due to friction forces. If the heat released at the same time heats the brake fluid beyond its permissible limit, it will boil and vapor locks will occur. The mixture of liquid and vapor will become compressible, the brake pedal may "fall through" and brake failure will occur. To eliminate this phenomenon, special brake fluids are used in hydraulic drives. They are usually classified by boiling point and viscosity in accordance with DOT standards - Department of Transportation (Department of Transportation, USA). Distinguish between the boiling point of a "dry" liquid that does not contain water and "moistened" - with a water content of 3.5%. Viscosity is determined at two temperatures: +100°C and -40°C. These indicators, corresponding to the American federal standard for vehicle safety FMVSS No. 116, are presented in the table. Similar requirements are contained in other international and national standards - ISO 4925, SAE J 1703, etc. In Russia, there is no single standard regulating the quality indicators of brake fluids, and domestic manufacturers work according to various technical conditions.

Brake fluids of various classes are mainly used:
- DOT 3 - for relatively slow vehicles with drum brakes or disc front brakes;
- DOT 4 - on modern high-speed vehicles with predominantly disc brakes on all wheels;
- DOT 5.1 - on road sports cars, where the thermal load on the brakes is much higher.
Note. DOT 5 class fluids are practically not used in conventional vehicles.

PERFORMANCE REQUIREMENTS

In addition to the main ones - in terms of boiling point and viscosity, brake fluids must meet other requirements. No negative impact on rubber parts. Rubber cuffs are installed between the cylinders and pistons of the hydraulic drive of the brakes. The tightness of these joints increases if, under the influence of brake fluid, the rubber expands in volume (for imported materials, an expansion of no more than 10% is allowed). During operation, the seals should not swell excessively, shrink, lose elasticity and strength.
Protection of metals from corrosion. Brake hydraulic drive units are made of various metals interconnected, which creates conditions for the development of electrochemical corrosion. To prevent it, corrosion inhibitors are added to brake fluids to protect parts made of steel, cast iron, aluminum, brass and copper.
Lubrication of friction pairs. The lubricating properties of the brake fluid determine the wear of the working surfaces of brake cylinders, pistons and lip seals.
Stability at high and low temperatures. Brake fluids in the temperature range from minus 40 to plus 100°C must retain their original properties (within certain limits), resist oxidation, delamination, as well as the formation of sediments and deposits.

TYPES OF BRAKE FLUIDS AND THEIR COMPATIBILITY

Brake fluids consist of a base (its share is 93-98%) and various additives, additives, sometimes dyes (the remaining 7-2%). According to their composition, they are divided into mineral, glycol and silicone.
Mineral, which are various mixtures in a 1: 1 ratio of castor oil and alcohol, such as butyl (red-orange liquid "BSK"). Such liquids have good lubricating and protective properties, are non-hygroscopic, and are not aggressive to paintwork. But they do not meet international standards in terms of their main indicators - they have a low boiling point (they cannot be used on machines with disc brakes) and become too viscous already at minus 20 ° C.
Mineral fluids must not be mixed with glycol fluids, otherwise the rubber cuffs of the hydraulic drive units may swell and the formation of castor oil clots.
Glycols based on polyglycols and their ethers are groups of chemical compounds based on polyhydric alcohols. They have a high boiling point, good viscosity and satisfactory lubricity. The main disadvantage of glycol fluids is hygroscopicity - the tendency to absorb water from the atmosphere. In operation, this mainly occurs through the compensation hole in the reservoir cap of the master cylinder. The more water dissolved in the brake fluid, the lower its boiling point, the greater the viscosity at low temperatures, the worse the lubricity of parts and the stronger the corrosion of metals. Domestic and imported glycol fluids of DOT 3, DOT 4 and DOT 5.1 classes are interchangeable, but it is undesirable to mix them, since the basic properties may deteriorate in this case.
On vehicles more than twenty years old, the seal rubber may not be compatible with glycol fluids - only mineral brake fluids must be used for them (or all seals will have to be changed).
Silicone, made on the basis of organosilicon polymer products. Their viscosity depends little on temperature, they are inert to various materials, workable in the temperature range from –100 to +350°C and do not adsorb moisture. Their use is particularly limited by insufficient lubricating properties. Silicone-based fluids are incompatible with others.
DOT 5 silicone fluids should be distinguished from DOT 5.1 polyglycol fluids as similar names can lead to confusion. For this, the packaging additionally indicates:
DOT 5 - SBBF ("silicon based brake fluids" - brake fluid based on silicone).
DOT 5.1 - NSBBF ("non silicon based brake fluids" - brake fluid not based on silicone).

CHECK AND REPLACE

On modern cars, due to a number of advantages, glycol brake fluids are mainly used. Unfortunately, in a year they can “absorb” up to 2-3% of moisture and they need to be replaced periodically, without waiting for the condition to approach a dangerous limit (see fig.). The replacement interval is indicated in the car's operating instructions and usually ranges from 1 to 3 years. An objective assessment of the properties of the brake fluid is possible only as a result of laboratory tests. In practice, the state of the brake fluid is assessed visually - in appearance. It should be transparent, homogeneous, without sediment. There are devices for determining the state of the brake fluid by boiling point or degree of moisture. But since the liquid does not circulate in the system, its condition in the tank (test point) may be different than in the wheel cylinders. In the tank, it comes into contact with the atmosphere, gaining moisture, but not in the brake mechanisms. But there the liquid is often very hot, as a result of which its original properties deteriorate.
Adding fresh brake fluid when bleeding the system after repair work does little to improve the situation, since a significant part of its volume does not change.
The fluid in the hydraulic system must be completely replaced. The sequence and features of this operation, for example, pumping with the engine running, depend on the design of the brake system (type of booster, availability of anti-lock devices, etc.). This information is often found in the vehicle owner's manual.

On domestic cars, the brake fluid is replaced in one of the following two ways.
1. Completely drain the old fluid by opening all valves (fittings) for releasing air from the hydraulic brake drive. Then fill the tank with fresh fluid and pump it into the system by pressing the brake pedal. The valves are sequentially closed when liquid appears from them. Then air is removed from each circuit (branch) of the hydraulic drive (“pumping” the brakes). With this method, the new fluid does not mix with the old. Part of the fresh liquid released during pumping can be reused (letting it settle and filtering).

Note. Prior to the start of the operation, a drain hose must be put on each valve, lowering its other end into a suitable container - leaking brake fluid can damage tires and paintwork on suspension parts, brakes, wheels.

2. Each circuit is pumped in turn, constantly adding fresh liquid to the master cylinder reservoir and thus displacing the old one, preventing the system from draining. This is continued until fresh fluid flows from the valve. With this option, air cannot get into the hydraulic actuator and control "pumping" is not required. But it is possible that some of the old fluid will remain in the system. In addition, more fresh fluid will be required than when pumping in the previous way. This is due to the fact that most of it, removed from the hydraulic drive, mixes with the old one and becomes unsuitable for further use.

SECURITY MEASURES

Store any brake fluid only in a hermetically sealed container so that it does not come into contact with air, does not oxidize, does not pick up moisture and does not evaporate.
Brake fluids are generally flammable or flammable. Smoking while working with them is prohibited. Brake fluids are poisonous - even 100 cm3 of it that gets inside the body (some fluids smell like alcohol and can be mistaken for an alcoholic drink) can lead to the death of a person. In case of ingestion of liquid, for example, when trying to pump out part of it from the reservoir of the master cylinder, you must immediately flush the stomach. If the liquid gets into the eyes, rinse them with plenty of water. And in any case, you should consult a doctor.

What is brake fluid? This is a special substance to ensure the braking of the car. It is in a liquid state and presses on the brakes after pressing the pedal. In other words, it provides a link between the driver's commands and the brake mechanism. If there is a violation of this connection, the car simply will not stop. This can happen if the fluid becomes too hot, causing steam to form inside the brake mechanism. It makes the system compressible, and the substance will not be able to associate pressing the pedal with hard deceleration and brake slamming. That is why brake fluid is a small, but very important part of a car. Without it, the driver will not be able to safely move in the stream. In other words, no brake fluid, no brakes.

Brake fluid is divided into several types, which differ in the temperature of its heating. So, the first classification divides this substance into "wet" and "dry" liquid. Naturally, the "dry" liquid includes less water, and in the "moistened" its share is 3-4%. Moreover, these two brake fluids are further divided into four groups: DOT 3, DOT 4, DOT 5 and DOT 5.1. The very first type withstands the lowest temperature: 205 degrees Celsius for "dry" and 140 for "moist". It is followed by DOT 4 (for cars with higher loads, they require more temperature, and therefore the second type of brake fluid is designed for 155 and 230. As for DOT 5.1 fluid, it can be found on sports cars, for example, on the BMW M6, Ferrari F458, and Others. But the penultimate type is almost never used on production cars. Most likely, DOT 5 is also installed on modified modifications of sports cars. By the way, it is quite possible that the most perfect liquid is on. Outstanding characteristics confirm this.

So, we have considered the types, but the question remains "which brake fluid is better?". How to answer it? Of course, DOT 5 will provide the best braking. As for production cars, this is DOT 5.1. Other types of fluids are more suitable for normal conditions and standard cars that are not designed for high speed and

Summing up, I want to pay attention to the components that make up the brake fluid. The composition of this substance is replete with diversity. For example, silicone brake fluid contains polymers, while glycogel fluids are composed of polyglycols. But they have something in common - additives. These include anti-corrosion and lubricants.

What is the main function of brake fluid? Of course, this is to ensure safety while driving. As mentioned above, without this substance there are no brakes. Therefore, it is important to treat it with special attention, because a leak can lead to dangerous consequences. The use of DOT 3 fluid on sports cars will not lead to anything good either, because large overloads lead to its excessive heating.

It should be noted that different liquids can be mixed, as long as they are on the same basis. If there is no relevant information on the label, then it's not worth the risk!

Brake fluid is part of the hydraulic brake system. This is a working fluid that transmits pressure from the master brake cylinder to the wheel cylinders.

That is, a liquid conducts pressure in much the same way that wires conduct electricity. And since the wires are not made from the first material that comes across, but from the one that is suitable, the fluid must have certain properties in order to be a good pressure conductor in the car's braking system.

The main properties of the brake fluid when working in brake systems:

- the brake fluid must remain a liquid, that is, under operating conditions, it must not boil or freeze;

the operating temperature of the brake fluid ranges from - 50 (in severe frost) to + 150 with dynamic acceleration. When the brake fluid boils, vapor bubbles force some of it into the expansion tank of the GTZ and into the piping system. The liquid remains in the system, mixed with vapor bubbles. But if the liquid itself is incompressible, then microscopic gas bubbles are easily compressible. In the presence of gas in the brake system, the transferred pressure will primarily go to compress the bubbles in their entire total volume, and only after that the pressure will be transferred to the liquid. With this outcome, the brake pedal will become soft, a sharp increase in effort will not be felt, and braking will be ineffective.

- the brake fluid must retain its properties for a long time;

according to the regulations for the operation of vehicles, the brake fluid must be replaced every 12 months or more, all this time the brake fluid must be ready for use in emergency situations.

moisture also affects the boiling point of the brake fluid, and as the concentration of water increases, the boiling point decreases. All this is due to the constant volume of dissolved gas in water and water boiling at 100 degrees Celsius, a temperature much lower than the upper limit of the working temperature of the brake fluid. Therefore, the brake fluid must have minimal hygroscopicity (moisture absorption). Moisture in the system contributes to the corrosion of brake cylinders and pistons, and in cold weather, hydrate plugs, obstruction of pipelines and, as a result, failure of the braking system may occur. In addition, at low temperatures, even if the brake fluid is not frozen, viscosity becomes a critical parameter - if it increases, then the brake response time will noticeably increase. So, in particular, in the standard developed by the International Association of Transport Engineers (SAE), it is directly stated that the viscosity of the brake fluid at -40 ° C should not exceed 1800 cSt (mm2 / s). In addition to SAE, brake fluid requirements are covered by US Department of Transportation regulations. Federal Society for Motor Vehicle Safety - U.S. department of transportation. Federal motor carrier safety administration. They have three regulatory classes: DOT-3, DOT-4 and DOT-5.1. but more on that later.

The graph shows the dependence of the boiling point of the Rosa brake fluid on the volumetric water content.

- do not react with RTI - rubber technical products that act as seals in the brake system;

When swelling changes in the shape and properties of rubber, gusts, gaps in seals (rubber rings) and pipelines (rubber hoses) are possible, leading to failure of the brakes.

Lubricate mechanically rubbing pairs to increase service life and prevent scuffing, excessive wear.

The lubricating properties of the fluid provide the longest and most reliable operation of the mechanical systems of the brake system.

Given such complex requirements, modern brake fluid is quite complex in composition.

Basic compositions used in brake fluids

Glycol - base for brake fluid

Most modern products (including Neva, Tom and Rosa) are based on glycol mixtures. Glycols (aka diols) are alcohols that have two OH hydroxyl groups each. The simplest representative of the glycol family is the well-known ethylene glycol used in the production of antifreezes and antifreezes.

Butyl alcohol + oil - brake fluid base

A few decades ago, BSK appeared - red brake fluid. It is made from butyl alcohol and castor oil, mixing them in a 1: 1 ratio (hence the name of the brake fluid - BSK). Today, this is history, since the properties that BSC provides are far from modern requirements for brake fluids. The main disadvantage is the low boiling point - only 115 ° C. In addition, the increased viscosity of BSC at sub-zero temperatures. The only significant plus of this brake fluid is that BSC does not absorb water.

Glycol ether + polyester - brake fluid base

Neva brake fluid is based on glycol ether mixed with polyester. An important ingredient in this fluid is an anti-corrosion additive. This liquid is highly hygroscopic and rapidly lowers its boiling point during use. Today, this liquid is considered obsolete and is not produced.

Figure 1 brake fluids DOT-3, DOT-4, DOT-5.1

Tom - this liquid also includes glycol ether and a package of targeted additives.
Compared to the Neva, Tom's main operational indicators have been improved. Therefore, it is classified as a class that meets the requirements of DOT-3.

The best brake fluid of domestic production

The most perfect mass product of the domestic glycol family is Rosa. This fluid is based on boron polyester with a special additive package. Therefore, it satisfies the DOT-4 class.
Rosa DOT-4 is fully suitable for use in the brake system of a modern car.

Highest brake fluid standard DOT 5.1

DOT 5.1 brake fluid is hygroscopic, non-corrosive and lasts longer than glycol-based DOT-3, DOT-4 brake fluids. The only disadvantage of this brake fluid is its low prevalence and high price.

Parameters of brake fluids depending on the standards.

Brake fluid	Manufacturer	Regulatory document according to which the brake fluid is made	DOT-3 class. Standard Dry / Wet Boiling Temperature (+205 /+ 140)	Class by DOT-4 Standard Dry/Wet Boiling Point (+230 /+ 155)	DOT-5.1 class. Standard Dry / Wet Boiling Temperature (+260 /+ 180)	"Dry" boil temperature	"Humidified" boil temperature
BSC	no information	no information	does not match	does not match	does not match	115	no info
"Neva"	no information	no information	does not match	does not match	does not match	195	138
"Tom"	OAO KHIMPROM, Kemerovo	TU 2451-076-05757618-2000	corresponds	does not match	does not match	220	150
"Dew"	NPP "MAKROMER", Vladimir	TU 2451-354-10488057-99		corresponds	does not match	260	165
ROSDOT	OOO "TOSOL-SINTEZ" Dzerzhinsk	TU 2451-004-36732629-99	performance properties are higher	corresponds	does not match	260	165
HYDRAULAN 408	BASF Germany	TTM 1.97.0738-2000	performance properties are higher	corresponds	does not match	no info	no info
DOT-4	LLC "Lukoil-Permnefteo- orgsintez" Perm	TU 2332-108-00148636-2000	performance properties are higher	corresponds	does not match	230	160
TORSA DOT-4	CJSC "BULGAR-SINTEZ" and CJSC "Bulgar Lada Plus", Kazan	TU 2332-001-49254410-2000	performance properties are higher	corresponds	does not match	230	160

BRAKE LIQUIDS used in VAZ vehicles

Since 1970, the clutch and brake systems of VAZ vehicles have been filled with NEVA brake fluid with a boiling point of 195 0C. In 1983 the "TOM" brake fluid with a boiling point of 215 0C was introduced, and in 1988 the "ROSA" brake fluid with a boiling point of 260 0C was introduced. Since all these liquids are hygroscopic, during operation their boiling point decreases, reaching limits that are dangerous in terms of the formation of vapor locks in the brake system. Such limit values ​​of the boiling point for TZh "NEVA" can be reached already after one year of operation, for TG "TOM" after two years, and for TG "ROSA" after three years.
For this reason, AVTOVAZ excluded the use of TZH "NEVA" from the technical documentation, limited the use of TG "TOM" to cars of the VAZ-2101 ... VAZ-2107 and VAZ-2121, VAZ-21213 models.
Technical requirements for DOT-3 and DOT-4 brake fluids are set out in TTM 1.97.0738-2000. TTM applies to brake fluids intended for hydraulic brake and clutch systems of VAZ vehicles of various models.

You can mix DOT 3, DOT 4 and DOT 5 on a silicone-free basis. All brake fluids listed below are compatible and can be mixed with each other.

1. ROSDOT LLC "TOSOL-SINTEZ", Dzerzhinsk, TU 2451-004-36732629-99
2. ROSA DOT-4 NPP "MAKROMER", Vladimir TU 2451-354-10488057-99
3. TORSA DOT-4 CJSC "BULGAR-SINTEZ" and CJSC "Bulgar Lada Plus", Kazan, TU 2332-001-49254410-2000
4. ROSA-DOT-3 NPP "MAKROMER", Vladimir, TU 2451-333-10488057-97
5. TOM OJSC "KHIMPROM", Kemerovo, TU 2451-076-05757618-2000
6. DOT-4 LLC "Lukoil-Permnefteorgsintez", Perm, TU 2332-108-00148636-2000
7. HYDRAULAN 408 DOT-4 BASF Germany ТТМ 1.97.0738-2000
8. MOTUL Hydraulic DOT 5 (based on polyglycols without silicone).

Do not mix the above brake fluids with mineral based (LHM) and silicone (DOT 5 silicone base) brake fluids.

That is, simply put, you can mix mineral with mineral, silicone with silicone and silicone-free based on polyglycols with similar brake fluids, so find on the bottle and carefully read the name of the brake fluid base and then just add it to the brake system.

Brake fluid used for ABS brake system

For brake systems with ABS, there are no specialized brake fluids and standard fluids with enhanced performance properties, that is, DOT-4 or DOT-5.1, are used for them.

Requirements for compliance with safety measures when working with brake fluids

Store the product in a tightly closed container without moisture.
Aggressive to varnishes, paints and leather.
In case of contact with skin, wash off with water.

Terms of operation and replacement of brake fluid

Replacement is made once every 12 or 24 months in accordance with the recommendations of the designers. AvtoVAZ regulates the terms - in two years or after 100 thousand kilometers.

Standards for brake fluid intended for vehicles.

Unfortunately, according to many industrial, technological procedures and standards, Russia has long lost its weight in the world and the relevance of using internal standards. At the moment, GOSTs are only advisory in nature, and TUs can be issued by anyone, registered at the standardization center and working on it. In this regard, the American DOT (Department of Transport) standard is actively used on the Russian brake fluid market, nothing more than the standard of the US Department of Transportation, this organization was mentioned earlier. It is Standard No. 116 for brake fluid intended for self-propelled vehicles that is currently the most popular and in demand when choosing a brake fluid.

Brake fluid is a very important component of any car. From the name it is clear that it is poured into the brake system and directly contributes to braking, that is, the system works on the hydraulic principle. But pour into the system, do not understand that it is impossible! There are many reasons for this; special compounds with certain properties are used here. Today I want to tell you - what they consist of and why they definitely need to be changed ...

By the way, I received such questions on my blog - “Tell me, is it possible to fill ordinary water into the brake system? And that will be?" It can be seen a young inquisitive mind, as they say - comprehends the world! Read on and you'll understand.

A few words about the brake system

I just want to remind you how it works. In any car there is a brake pedal, if you "roughly exaggerate" it is connected with the brake working cylinder. After you press this pedal, pressure is created in the brake system, it presses on special pistons in the brake calipers (or rear cylinders) that compress (in the case of front-wheel drive) or spread (in the case of rear-wheel drive) brake pads. And already they, in turn, squeeze the brake disc or stop the drum from the inside, I advise you to read -.

I think everyone knows the principle of operation of this system, in our article it is necessary for the next understanding of the material.

System warm-up

When braking, the discs or drums get very hot. Actually, this is a law of physics, friction occurs - brake pads rub against a metal surface, there is a large release of heat. The pads are made of a special “thermo” and “wear-resistant” material, so they can walk for a very long time, this material does not heat up as much when compared to discs or drums.

But their heating can be simply catastrophic (especially near the front axle) there are a lot of videos on the Internet where they heat up to “red”.

And what happens - parts of the brake system, namely pistons, cylinders, and even experience huge temperature loads. At high speeds, temperatures can reach up to 150 degrees Celsius. Do you understand what I mean? Actually now we will start talking about the compositions.

What can and cannot be uploaded

Now I want to answer the reader - let's take a look at ordinary water. Why is it STRICTLY IMPOSSIBLE to FILL. YES, actually, everything is simple - even if you don’t dig deep, water boils and evaporates at high temperatures, and at low temperatures it freezes already at -1 degree. You come in this winter, start the car, but there are no brakes! The system is frozen! Also imagine - the system boils when braking, steam pours out of the system tank, the efficiency is at zero. However, even if freezing and boiling are hypothetically defeated, then water has ONE BIG DEFECT - it oxidizes and provokes rust, after a short period of time, the pistons in the calipers will simply rust, the seals that are designed to walk on a smooth and clean surface will break and water will flow out.

Alcohols (in pure form) are also not suitable, because they boil, and even ignite.

Transmission oils, motor oils - oils may be suitable, but again, not all.

They have really low evaporation, they also resist high temperatures very well (especially motor ones), but at low temperatures they can thicken (this negatively affects fluidity), and they can also negatively affect the rubber of the oil seals! That is, calipers or cylinders can leak.

Different formulations of brake fluid

So what did we understand - that the brake fluid must have high fluidity, lubricate, protect against corrosion, not freeze, withstand temperatures in the range of 150 - 170 degrees Celsius, not boil! THAT is such - "super liquid".

Probably, I won’t surprise anyone by saying that “brakes” are still evolving - WELL, NOW THERE IS NO IDEAL COMPOSITION WHICH WOULD 100% MEETING ALL REQUIREMENTS.

Mineral compositions - it all started with them, I will say that they were used on old cars that did not even have front disc brakes, only drums. YES, and speeds at that time rarely exceeded 60 km / h.

Their composition has long been known - castor oil with the addition of butyl or ethyl alcohol, this is a kind of base, but many manufacturers mixed other minerals and petroleum products of various degrees of purification into the composition. It is difficult to call such a composition ideal, but there are still positive points:

• They lubricate well.
• They practically do not absorb moisture, that is, if we say “scientifically”, they have low hygroscopicity

However, there are more cons:

• At temperatures of 110 - 130 degrees boil
• At -20 degrees they begin to thicken
• In addition, castor oil adversely affects parts made of brass, aluminum, copper
• Also, for a long time they could not find a formula that, over time, would not decompose rubber products - oil seals, cuffs, etc.

For a very long time they fought over the formula with castor oil, added all kinds of additives and other substances, but its time has already passed.

Glycol brake fluids - are now used quite widely, you can know under the abbreviations (DOT3, DOT4, DOT 5.1). They contain polyethylene glycols and polyesters of boric acid, comply with all international standards, and have also passed the Russian GOST certification.

This composition is almost perfect, boils at + 150, + 200 degrees, perfectly lubricates, protects against rust, is almost neutral to rubber elements.

The minus here is one and quite large - high hygroscopicity, they absorb moisture very strongly, so it is MANDATORY to change it every 2-3 years! Otherwise, the calipers begin to turn sour and rust.

Silicone brake fluids (DOT5 and special version DOT-5.1/ABS). The composition here is completely different from the counterparts, based on organosilicon polymers. There are enough pluses - it does not absorb moisture, it is absolutely neutral to rubber and metals, it is always fluid (it does not depend on temperature).

There are also disadvantages, and where without them - the lubricating properties are at a low level, so there is more wear on the seals (when compared with counterparts). Such compositions are rarely used on serial versions of cars; as a rule, they are poured into sports or racing cars, where the heating of the calipers is much higher.

The instructions for the car of any manufacturer always indicate that it is compatible with this machine. Of great importance is the composition of the brake fluid. The chemical components of the fluid can affect the brake system in different ways. Incorrectly selected brake fluid can deform the parts of the system and disrupt its operation, up to brake failure.

What is the composition of the brake fluid?

High-quality brake fluid is the key to the perfect operation of the brake system. The main parameters by which quality is determined are:

Boiling temperature. Brake fluid should not boil at relatively low temperatures, because a lot of heat energy is generated during the operation of the brake system. If the liquid boils easily, the resulting vapor bubbles are compressed and interfere with the braking force. And this means that the brakes may stop working.

Viscosity. At low temperatures, the properties of the brake fluid are also very important. It should circulate well through the system. Frozen liquid blocks work, too viscous slows it down, and excessive liquid increases the possibility of leakage;

The main characteristics of the brake fluid are the boiling point, viscosity and hygroscopicity.

Hygroscopicity. The less moisture the brake fluid can absorb, the better. After all, excess moisture is a rapid boiling of a liquid, thickening at low temperatures and another change in its properties. A liquid with changed properties no longer performs its functions and needs to be replaced.

In addition to these characteristics, the anti-corrosion and lubricating properties of the fluid are important - they provide a long life for pistons, cuffs and cylinders. Also, the liquid should not deform the rubber parts of the system.

Can you mix?

It is possible to mix with each other or fill in a new liquid without first cleaning the system in only one case - when glycolic liquids simply belong to different classes (DOT 3, DOT 4 and DOT 5.1). But still, manufacturers recommend mixing liquids of the same class, and even better - of the same brand.

Mineral and glycol fluids do not combine with each other; if they are mixed, the rubber cuffs of the hydraulic drive are deformed. Liquids in which silicone is present are categorically incompatible with any other. Chemical reactions in the case of mixing such fluids with others are aggressive to the details of the system and completely change the properties of the brake fluid.