It helps us to maintain the brake system in our car in good condition, thanks to which the brakes in the car will be in good condition and will not fail in the event of an emergency on the road. This fluid in the car is responsible for transferring pressure from the brake pedal to the brake units in the wheels. In other words, brake fluid makes sure that all components of the brake system work together properly and as a whole. In order to do this job all year round at all ambient temperatures, the brake fluid must withstand extreme temperatures without boiling or freezing. Unfortunately, over time, brake fluid loses its properties and becomes contaminated. Therefore, in any car, it must be periodically replaced with a new one.
If you do not change the brake fluid in time, then many brake components of the car can fail. As a result, this can directly affect your security.
It is important to know:
Accordingly, every driver must (must) regularly check the level of the brake fluid and its condition. Our guide will help you check the brake fluid level in your car. You will also learn whether or not to add new fluid when you need to completely replace the brake fluid and can learn how to identify a potential fluid leak in your vehicle's brake system.
Master brake cylinder
Beware of fluid leakage
What you need to know about brake fluid
Brake fluid is hygroscopic (absorbs moisture) to help protect brake components. * Brake fluid is light yellow in color * Does not shrink when compressed, ideal for automotive braking applications * Lubricates pistons in the brake master cylinder, caliper pistons and wheel brake cylinders * Brake fluid lubricates the rubber seals in the main brake cylinder and in the brake cylinders mounted on the wheels. * Brake fluid has good resistance to temperature changes * Brake fluid DOT 3 has a boiling point of 205 degrees * liquid boiling point DOT 4 230 degrees * After two or three years of use, the moisture content of the brake fluid rises, which eventually leads to the onset of corrosion of the brake elements and loss of fluid properties. * When using brake fluid, it is recommended to use only the fluid specified by the vehicle manufacturer in the vehicle owner's manual.
Master brake cylinder
The master brake cylinder works like a pump that supplies brake fluid under pressure to each wheel where the car's brakes are located. That is, every time you apply the brake pedal, the brake master cylinder pumps fluid, directing it throughout the car's brake line.
The master brake cylinder also has a brake fluid reservoir. Thus, in order to check the brake fluid level, you must find this reservoir under the hood of your car.
As a rule, the main brake cylinder is installed on the vacuum brake booster. The brake booster (large round component under the hood of a car) is usually mounted on the driver's side at the rear of the engine compartment. The brake master cylinder is a small metal cylinder with thin metal tubes coming out of the cylinder, over which a metal or plastic container (reservoir) is mounted. This container is filled with brake fluid.
Checking the brake fluid level
New car models (from the mid-1980s to today) use a translucent container (reservoir) attached to the brake master cylinder. Thanks to the transparency of the container, you do not need to unscrew the cap to check the brake fluid level. When checking the brake fluid level, remember that it must be between the "MIN" mark (minimum mark) and the "MAX" mark (maximum mark).
It is worth noting that some car models (including older ones) have a non-transparent metal reservoir for storing brake fluid. Therefore, to check the liquid level in a metal container, it is necessary to remove the cap.
Before removing the cap from the brake fluid reservoir, be sure to wipe the cap free of dust, oil, dirt, etc. using a clean cloth. This will protect the brake system from contamination before removing the brake fluid reservoir cap.
On older models of cars (and on some modern ones), in order to remove the cover, you may need a screwdriver, which you need to lift the spring clip, or unscrew the bolt at the top of it.
After unscrewing the cap of the brake fluid reservoir, inspect the fluid. If you don't see a solid line marked inside the tank, make sure the fluid level is about 6mm from the top of the tank.
If during the inspection it turned out that the level of the brake fluid is low, then you will have to add it to the optimum level. To do this, use the type of fluid that is recommended by the car manufacturer (usually this is brake fluid DOT 3 or DOT 4).
In some car models, the type of brake fluid used is also indicated under the brake fluid reservoir cap.
If you do not have a manual for the operation of the car, then you can buy or download a manual for the repair and maintenance of your car on the Internet. As a rule, such books contain information about the brand and type of brake fluid used.
You can also contact any auto shop, where the VIN number of your car will determine which brake fluid is used in it.
To get a visual idea of how to check the brake fluid level in a car, you can watch some videos below.
Now that you know how to check the brake fluid level, it's time to check the condition of the fluid, that is, its property.
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Help site: Over time, the brake fluid level may drop, either as a result of fluid leakage from their system, or due to wear on the brake pads, brake discs, or brake drums (if equipped). As a result of the natural wear of the brake components, the gap between the parts increases, resulting in a decrease in the brake fluid level. Thus, a slight decrease in the level of brake fluid is a completely normal process during vehicle operation. If you notice that the level of the brake fluid has dropped sharply in a short time, then there is a high probability that there is a leak in the brake system that must be found. |
7 Reasons Why You Should Check Your Brake Fluid
If you regularly check the level of the brake fluid, this does not mean that you monitor the condition of the brake system. In addition to the level, you should also regularly check the condition of the fluid to determine if the brake fluid has lost its chemical properties.
So if you have never tested the properties of a brake fluid, here are 7 reasons why you should definitely do it:
- - Brake fluid contains some alcohol and absorbs moisture
- - Moisture will interact with the metal parts of your brake system and cause them to corrode over time
- - and the seals of the brake system wear out over time and become contaminated from the brake fluid
- - As a rule, the main brake cylinder wears out first, which begins to flow
- - If, as a result of leakage of brake fluid from the master cylinder, it enters the main brake booster, it will have to be replaced
- - Brake fluid, as a rule, should not be used for more than 2-3 years of vehicle operation (with a mileage of no more than 20,000-30,000 per year). After that, the brake fluid completely loses its properties. As a result, due to bad fluid in your car, they may suddenly fail completely.
- - Also, if you do not change the brake fluid in time, your brake system may fail. Especially if yours is equipped with ABS. In this case, the repair can be several thousand dollars.
How to check the properties of the brake fluid
Some car manufacturers recommend, as we have already said, changing the brake fluid every two years. Some vehicle manufacturers state that the brake fluid change interval should be every five years. But some produced sometimes do not indicate the service life of the brake fluid. But this does not mean that the brake fluid is eternal. We did not advise changing the fluid very infrequently. This is especially true for the operation of a car in our country, where conditions are much more severe than in the same Europe.
Unfortunately, many car owners do not pay due attention to the brake fluid, forgetting to check not only its level in the reservoir, but also change it to a new one after a certain period of operation of the car. As a result, an incorrect fluid change interval leads to contamination and corrosion of the brake system.
Many factors influence the properties of brake fluid. For example, changes in climatic conditions throughout the year, the moisture content in the environment, the condition of the brake system and the removal of the brake fluid reservoir cap directly affect, which eventually begins to corrode the components of the brake system over time.
That is why it is so important to check not only the level of the brake fluid, but its condition. We recommend checking the brake fluid twice a year and replacing it with new fluid every two to three years, even if your car manufacturer recommends that you change your brake fluid at longer intervals of ownership.
Many also mistakenly believe that the condition of the brake fluid can be determined by its color. But in reality, the color of the fluid cannot accurately tell you the actual properties of the brake fluid.
Yes, when the fluid is new it is usually a clear light yellow color which can darken over time. But a change in color is not necessarily an indication of deterioration in the properties of the brake fluid.
On the other hand, contamination of the fluid (with the exception of the accumulation of moisture) can lead to darkening of the brake fluid.
The easiest and most practical way to check the condition of the brake fluid is to use brake fluid test strips. You can buy test strips at a car dealership or order them online.
Testing the property of a liquid will only take 1 minute.
Checking brake fluid with test strips
1. To test the brake fluid, you must clean the fluid reservoir cap from dust, dirt, etc. with a clean cloth and then open it.
2. Then take the test strip out of the package.
3. Dip the test strip partially into the brake fluid reservoir.
4. Install the brake fluid reservoir cap back.
5. Wait 30 to 60 seconds for the liquid to react with the chemicals applied to the test strip.
6. Look at the surface of the test strip, and compare them with the samples indicated on the package (see the description of the test samples on the package or in the instructions for the test strips).
7. If the color of the test strip has changed, then this indicates that the brake fluid in your car is in good condition.
Thanks to these test strips, you will save yourself the question of whether to change the brake fluid to a new one.
In addition, the Russian market also has electronic testers with which you can check the condition of the brake fluid. But, unfortunately, the cost of such devices is justified only for the use of testers or private auto repair shops.
Knowing how to check brake fluid, you can in the easiest way. By changing the brake fluid in time and monitoring its level in the brake system, you contribute to the long service life of the entire brake system. If you do not monitor the brake fluid in the car, this can lead to premature failure of the brake system, the repair of which can be very expensive.
Thus, check the brake fluid level at least once a month or every time you lift the hood of your car. But try not to lift the cap of the brake fluid reservoir frequently to avoid the rapid saturation of the fluid with moisture contained in the air.
Also check the condition (property) of the brake fluid once every two years and, if necessary, replace it with a new one.
Brake fluid is a type of hydraulic fluid that is used in hydraulic brake systems and hydraulic clutch systems on automobiles, motorcycles, light trucks as well as bicycles. The fluid is used to transmit pressure and to increase braking force.
General information about brake fluid
The principle of operation of the brake fluid is its low compressibility. Molecules do not have an internal void, so when compressed, the volume of the liquid does not decrease, and the pressure quickly spreads to the entire volume.
The composition of the brake fluid
Brake fluid comes in many types, but is usually made from a low viscosity solvent, such as alcohol, and a viscous, non-volatile substance, such as glycerin.
Based on polyethylene glycol, brake fluid is produced under the brands DOT 3, DOT 4 and DOT 5.1.
Based on silicone - organosilicon polymer products grade DOT 5.
For vehicles with anti-lock braking systems, DOT 5.1/ABS brake fluids based on silicone and glycols can be used. About brake fluid wiki: link.
Characteristics and properties of brake fluid
In order for the brake system to work properly, the brake fluid must have certain characteristics and meet quality standards.
Boiling temperature. New brake fluid does not contain moisture, so its boiling point is within acceptable limits. But over time, moisture from the surrounding air enters the fluid, usually 1-2% per year of the total volume, but the characteristics of the brake fluid begin to change.
During braking, the working fluid heats up to very high temperatures due to friction. At this point, it is very important that the brake fluid does not boil, as in this case, moisture evaporates from the fluid in the form of vapor. And steam is dangerous because it is easily compressible and the pressure on the brakes will be less during the next braking, since the compressible steam will take away part of the volume.
The boiling point of brake fluid is directly related to the amount of water in it. The more water, the lower the boiling point and the greater the chance of "losing" the brakes.
Hygroscopicity. Some brake brands have minimal hygroscopicity (moisture absorption), for example, DOT 5, and can maintain the necessary characteristics throughout their entire service life. But the most common brands DOT 3, DOT 4 and DOT 5.1 are gradually losing their properties due to the increasing amount of moisture in them.
Viscosity. How the brake fluid will be pumped throughout the system will depend on this characteristic. And it should pump well and at -30 degrees Celsius and at 200 degrees, during braking.
If the liquid freezes completely or in places, then this blocks the operation of the brakes. Too thick fluid will be difficult to pump throughout the system, which will either lead to poor braking or different force on different wheels. Too liquid will cause leaks.
Corrosion protection. The brake fluid itself acts as a corrosion protection inside the brake system. At the same time, protection must be provided even with small amounts of moisture inside the system.
Corrosion protection is provided by special additives. They also provide protection for the sealing elements.
Compressibility. Ideally, the brake fluid should not compress at all, but there are certain tolerances for this characteristic. The main thing is that the liquid works equally well under different temperature conditions.
| "Dry" boiling point, °C | "Wet" boiling point (water 3.5%), °C | Viscosity, mm 2 /s |
Main Components | |
| DOT 2 | 190 | 140 | — | castor oil/alcohol |
| DOT 3 | 205 | 140 | 1500 | Glycol |
| DOT 4 | 230 | 155 | 1800 | Glycol / Boric acid |
| LHM+ | 249 | 249 | 1200 | Mineral oil |
| DOT 5 | 260 | 180 | 900 | Silicone |
| DOT 5.1 | 260 | 180 | 900 | Glycol / Boric acid |
Brake Fluid Compatibility
For topping up, you can use a liquid from the same manufacturer, but subject to the principles:
- only liquid with a higher rating number can be added, that is, DOT 4 can be poured into DOT 3, and DOT 5.1 can be poured into DOT 4.
- Do not mix DOT 5 with other brands - DOT 3, DOT 4, DOT 5.1.
- Do not mix mineral (eg LHM+) and glycol fluids.
If you break the rules, this will lead to a serious change in the characteristics of the liquid for the worse.
How often to change the brake fluid
The question of when to change the brake fluid can be answered unequivocally: once every two years or after 40,000 runs. These are general recommendations.
If the car is operated in severe conditions, then change the brake fluid more often.
Regular topping up cannot fully compensate for changes in the properties of the liquid - the boiling point drops, the chemical composition changes, anti-corrosion additives work worse. You can use the topping up method only when carrying out repairs or in case of a leak, when you just need to get to the service station or garage.
You can identify unsuitable brake fluid:
- Through a complete analysis using special equipment.
- "By eye" - the old liquid is dark in color, while the new one is translucent.
- A device that measures the amount of moisture in a liquid. If less than 3.5 percent, then you can still ride.
It is necessary to fill in the brake fluid in the expansion tank of the brake system. It is usually located above the master brake cylinder and serves to compensate for the brake fluid when it is heated, as well as to prevent air from entering the system.
The fluid level in the tank must be between the "MIN" and "MAX" marks. In modern cars, there is a float with a sensor that will notify the driver that the fluid level in the reservoir has dropped below the minimum mark.
How to change brake fluid
It is best to do this at specialized service stations. Most modern cars have an ABS system, and this leaves its mark on the procedure. Special equipment is needed to bleed the system with new fluid.
If you are told that it is possible to change the brake fluid without bleeding without special equipment, then do not listen to these tips. Yes, on some wheels the pressure from the reservoir can push through the system, but on all it will not work. As a result, air or old fluid will remain in the system. At the service station, the fluid is replaced under pressure, so subsequent pumping is not required.
The replacement procedure itself is as follows. New liquid is poured into the empty expansion tank of the cooling system, after which pumping occurs on each line, during which the new liquid displaces the old one.
The volume of brake fluid averages from 0.75 to 1.3 liters.
Visually replacing the brake fluid without special equipment is described in the video below:
brake fluid prices
Typically, prices for DOT 4 brake fluid fluctuate around 600-700 rubles per 1 liter. Some manufacturers ask for 1,500 rubles for a similar brand.
DOT 5.1 costs from 1,100 rubles, depending on the manufacturer.
Security measures
To prevent the brake fluid from oxidizing, evaporating and absorbing moisture, it must be stored in an airtight container.
They are generally flammable, so keep them away from open flames and high temperatures.
In no case should you drink, even a small amount will lead to poisoning. In case of contact with the eyes, rinse them thoroughly with clean water and consult a doctor.
Brake fluid is an important component of the braking system. Its main purpose is to transfer force from the master brake cylinder to the wheel cylinders.
Since most liquids are practically incompressible, the pressure will be transmitted through the liquid, and after a negligible time will be the same in the entire volume occupied by this liquid. 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, so the liquid must have certain properties in order to be a good conductor of pressure.
In brake systems with a hydraulic drive, the following brake fluids are mainly used: BSK, Neva, Tom, Rosa - in domestic cars, SAE J 1703ISO 4925, DOTZ, DOT4, BOT4 +, DOT5.1, DOT5, Racing Formula DOT 6 - in foreign cars.
Basic properties of brake fluid
1.BOILING POINT
The main parameter of the brake fluid is its boiling point - the higher it is, the better for the brake system. Boiled brake fluid bubbles and the effectiveness of the brake system is reduced.
The higher it is, the less likely it is that a vapor lock will form in the system. When the car brakes, the working cylinders and the fluid in them heat up. If the temperature exceeds the allowable temperature, the TJ will boil and vapor bubbles will form. The incompressible fluid will become “soft”, the pedal will “fall through”, and the car will not stop in time.
brake fluids
Brake fluid is one of the most important operating fluids in a car, the quality of which determines the reliability of the brake system and safety. Its main function is to transfer energy from the brake master to the wheel cylinders, which press the brake linings against the brake discs or drums. 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 (castor), glycol and silicone.
Mineral (castor)- which are various mixtures of castor oil and alcohol, for example, butyl (BSC) or amyl alcohol (ASA) have relatively low viscosity-temperature properties, as they solidify at a temperature of -30 ... -40 degrees and boil at a temperature of +115 degrees.
Such liquids have good lubricating and protective properties, are non-hygroscopic, and are not aggressive to paintwork.
But they do not meet international standards, 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 fluids on a different basis, as swelling of rubber cuffs, components, hydraulic drives and the formation of castor oil clots are possible.
Glycolic brake fluids consisting of an alcohol-glycol mixture, multifunctional additives and a small amount of water. 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). 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 brake fluid "Neva" has a boiling point of at least +195 degrees and is painted light yellow.
Hydrobrake fluids "Tom" and "Rosa" similar in properties and color to "Neva", but have higher boiling points. For the Tom liquid, this temperature is +207 degrees, and for the Rosa liquid, it is +260 degrees. Taking into account hygroscopicity at a moisture content of 3.5%, the actual boiling points for these liquids are +151 and +193 degrees, respectively, which exceeds the same indicator (+145) for the Neva liquid.
In Russia, there is no single state or industry standard that regulates the quality indicators of brake fluids. All domestic manufacturers of TJ work according to their own specifications, focusing on the standards adopted in the United States and Western Europe. (Standards SAE J1703 (SAE - Society of Automotive Engineers (USA), ISO (DIN) 4925 (ISO (DIN) - International Organization for Standardization and FMVSS No. 116 (FMVSS - US Federal Motor Vehicle Safety Standard).
The most popular at the moment are domestic and imported glycol fluids, classified by boiling point and viscosity in accordance with DOT - Department of Transportation (Department of Transportation, USA).
Distinguish between the boiling point of a "dry" liquid (containing no water) and humidified (with a water content of 3.5%). Viscosity is determined at two temperatures: +100°C and -40°C.
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▪ 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.
*Mixing glycol-based brake fluids is possible, but is not recommended as it may degrade fluid performance.
* On vehicles more than twenty years old, the seal rubber may not be compatible with glycol fluids - only mineral brake fluids should be used.
Silicone are 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. But their use is 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").
DOT 5 class fluids are practically not used in conventional vehicles.
In addition to the main indicators - in terms of boiling point and viscosity, brake fluids must meet other requirements.
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.
Impact on metals. 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.
Lubricating properties. The lubricating properties of the brake fluid determine the wear of the working surfaces of brake cylinders, pistons and lip seals.
thermal stability Brake fluids in the temperature range from minus 40 to plus 100°C must retain their original properties (within certain limits), resist oxidation, delamination, and the formation of sediments and deposits.
Hygroscopicity The tendency of polyglycol-based brake fluids to absorb water from the environment. The more water dissolved in TF, the lower its boiling point, TF boils earlier, thickens more at low temperatures, lubricates parts worse, and the metals in it corrode faster.
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. The replacement interval is indicated in the car's operating instructions and usually ranges from 1 to 3 years or 30-40 thousand km.
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. 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.
It is necessary to 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 absorb moisture and does not evaporate, in this case the fluid is stored for up to 5 years.
Brake fluid is a special substance that fills the brake system of the car and plays a crucial role in its operation. It transmits the force from pressing the brake pedal through the hydraulic drive to the brake mechanisms, due to which the vehicle is braked and stopped. Maintaining the correct quantity and quality of brake fluid in the system is the key to safe driving.
Purpose and requirements for brake fluids
The main purpose of brake fluid is to transfer force from the master brake cylinder to the brakes on the wheels.
Brake fluid
The stability of a car's braking is also directly related to the quality of the brake fluid. It must meet all the basic requirements for them. Additionally, you should pay attention to the manufacturer of the liquid.
Basic requirements for brake fluids:
- High boiling point. The higher it is, the less likely the formation of air bubbles in the liquid and, as a result, a decrease in the transmitted force.
- Low freezing point.
- The fluid must maintain the stability of its properties throughout its entire service life.
- Low hygroscopicity (for glycol bases). The presence of moisture in the fluid can lead to corrosion of the elements of the brake system. Therefore, the liquid must have such a property as minimal hygroscopicity. In other words, it should absorb moisture as little as possible. To do this, corrosion inhibitors are added to it, protecting the elements of the system from the latter. This applies to glycol-based fluids.
- Lubricating properties: to reduce wear of parts of the brake system.
- No harmful effect on rubber parts (o-rings, cuffs, etc.).
The composition of the brake fluid
Brake fluid consists of a base and various impurities (additives). The base makes up to 98% of the composition of the liquid and is represented by polyglycol or silicone. In most cases, polyglycol is used.
Ethers act as additives, which prevent the oxidation of the liquid by oxygen in the air and during strong heating. Additives also protect parts from corrosion and have lubricating properties. The combination of the components of the brake fluid determines its properties.
Liquids can only be mixed if they consist of the same base. Otherwise, the main performance characteristics of the substance will deteriorate, which may lead to damage to the elements of the brake system.
Brake fluids are divided into several types. The classification is based on the boiling point of the liquid and its kinematic viscosity according to DOT (Department of Transportation) standards. These standards are adopted by the US Department of Transportation.
Kinematic viscosity is responsible for the ability of the fluid to circulate in the brake line at extreme operating temperatures (from -40 to +100 degrees Celsius).
The boiling point is responsible for preventing the formation of a vapor "plug" that forms at high temperatures. The latter can lead to the fact that the brake pedal does not work at the right time. In terms of temperature, the boiling point of a “dry” (without water impurities) and a “moistened” liquid is usually taken into account. The proportion of water in the "moistened" liquid is up to 4%.
Classification of brake fluids There are four classes of brake fluids: DOT 3, DOT 4, DOT 5, DOT 5.1.
- DOT 3 withstands temperatures: 205 degrees for a “dry” liquid and 140 degrees for a “moistened” one. These fluids are used under normal operating conditions in vehicles with drum or disc brakes.
- DOT 4 is used on vehicles with disc brakes in urban traffic (acceleration-braking mode). The boiling point here will be 230 degrees - for a "dry" liquid and 155 degrees - for a "moistened". This fluid is most common on modern cars.
- DOT 5 is silicone based and is not compatible with other liquids. The boiling point for such a liquid will be 260 and 180 degrees, respectively. This fluid will not corrode paint or absorb water. On production cars, as a rule, it does not apply. It is usually used on special vehicles operating in conditions of extreme temperatures for the brake system.
- DOT 5.1 is used in sports cars and has the same boiling point as DOT 5.
The kinematic viscosity of all types of liquids at a temperature of +100 degrees is no more than 1.5 square meters. mm / s., and at -40 - it varies. For the first type, this value will be 1500 mm^2/s, for the second - 1800 mm^2/s, for the latter - 900 mm^2/s.
As for the advantages and disadvantages of each type of liquid, the following can be distinguished:
- the lower the class, the lower the cost;
- the lower the class, the higher the hygroscopicity;
- impact on rubber parts: DOT 3 corrodes rubber parts, and DOT 1 fluids are already fully compatible with them.
When choosing a brake fluid, the car owner must follow the manufacturer's instructions.
Features of operation and replacement of brake fluid
Brake Fluid Operation How often to change the brake fluid? The service life of the fluid is set by the automaker. Brake fluid must be changed on time. Do not wait until her condition approaches critical.
You can visually determine the state of a substance by its appearance. Brake fluid must be homogeneous, clear and without sediment. In addition, car services evaluate the boiling point of a liquid with special indicators.
The required period for inspecting the condition of the liquid is once a year. Polyglycol fluid needs to be changed every two to three years, and silicone fluid every ten to fifteen years. The latter is distinguished by its durability and chemical composition, resistant to external factors.
