Modern brake fluids are quite technologically advanced, they withstand high temperatures, as well as high pressure in the brake system of a modern car. They are not compressible and therefore they are used in the braking system of a car, that is, it will not work to compress - as we say, gas or air. That is why the car's system is liquid, it has proven its reliability (to be fair, it should be noted that there are also pneumatic options). BUT still the hydraulic version has small cons- it can leak out, for example, when it breaks brake hose but you have to go! But what if you don’t have exactly the same composition as you have (the original from the dealer is flooded)? Then a fair question arises - is it possible to mix brake fluid various manufacturers And different classes let's say pour DOT3 into DOT4 - what will happen? As usual, the article will have an extensive + video version at the end, so read on - watch ...
It is worth noting that brake fluid a long period of evolution has passed, as usual, everything was born from mineral compounds, then glycolic (now the most commonly used), then silicone (many write the future for them, but I do not quite agree) appeared. So what caused such a leap in development? YES, everything is simple, the cars are getting faster, the speeds are prohibitive, and therefore the mineral mixtures that used to be trite do not meet these requirements.
Dry and Wet Mix
At the very beginning, I want to talk about the hygroscopicity of brake fluid (for those who do not know, this is the ability to absorb moisture from environment). That is why it is mandatory on average after 2 - 4 years, it all depends on the class (more on that below).
So when you just opened a sealed jar (which had no contact with the surrounding air), and want to pour into the main tank, then such a composition will be called - DRY because there is no moisture at all! After all, they just opened.
But if your car or open jar was in contact with air (the jar could lie open on the shelf for a couple of years). That liquid has already absorbed a large percentage moisture! Moreover, only 3.5% is enough so that it can no longer be used in the brake system! Such a mixture is called - HUMIDIFIED (it is banal that it contains water)!
Classification byDOT
To begin with, what is DOT in general - if you decipher it, it turns out that the Department Of Transportation (Or the Department of Transportation) is located in the jurisdiction of the United States. So this department decided to demarcate various formulations by class - as a result, DOT1 appeared, and then others.
DOT1- DOT2 - these are the very first brake fluids, they were based on mineral substances, now they are practically not used, so we will not bother with them, although I will note them for general development. They were used on low-speed vehicles, speeds up to about 40 - 60 km / h, with heavy loads could boil fairly quickly. Because of this, they quickly lost their characteristics.
Now a small remark - ask, why could it boil? Yes, everything is simple when the car slows down, and the slope is protracted, wheel disks can heat up to 350 - 400 degrees Celsius. Part of the heat is transferred to the calipers, and from them to the “brake” itself. Mineral began to boil already at 140 degrees.
DOT3 - this is the third class, it was kind of innovative. In its composition, a glycol base has already been used. Boiling temperature dry liquid - 230, and wet - 140 degrees .
DOT4 - the fourth grade, do not believe the third was not enough, especially in a state of moisture. The basis is again glycols. The compositions have been slightly improved, and now the characteristics 240 and 155 respectively . Worth noting for most cars on this moment this is enough, but there are cars with powerful motors, heavy bodies and exorbitant speeds.
- for them the next class (why with a dot you will understand later). There is also a glycol component in the base. BUT the temperature threshold is again increased up to 260 and 180 degrees actually . However, these compounds are much more expensive, so they are rarely used on budget cars.
As you understand it, so to speak, is the “glycol branch” of development. Such compositions have many advantages, because not only boiling is important for us, but also lubrication with inside- these are pistons, seals, cylinders, etc. (it should be noted that seals work with glycols very well and for a long time). Also, these brake fluids are quite stable. That is, they do not have any deviations in the characteristics.
Of the minuses - replacement every 2 - 3 years, because hygroscopicity is very high level. It should be noted that this is a really "fat" minus.
DOT5 – fifth generation, there is more ABS In fact, they are very similar. In general, they were made as something revolutionary, they were supposed to supplant the old compositions and become the leader. The thing is that silicones are the basis. Temperature characteristics are approximately the same - it's 260 for dry and 180 for wet . But a big plus is hygroscopicity here it is not as big as that of opponents! You can operate 4 - 5 years without fear, yet silicone does not absorb moisture so much.
It seems to be the perfect long-term composition. But it turned out that there are also significant disadvantages.
Silicones do not have such lubricating properties as the opponent. Because of this, the wear of seals, cylinders, pistons occurs much faster. That is why the manufacturers returned back to the previous formula, and the “5.1” generation appeared. The introduction was long, but it is necessary to understand whether it is possible to mix or not
What happens if you mix brake fluids
Now the fun part, that's what we're here for. Whether it can be mixed or not. As we understood, there are two main subspecies, we will conditionally call them:
GLYCOLS are DOT3, DOT4, . They can be mixed in any ratio, if you want they are interchangeable, nothing bad will happen! HOWEVER, THERE IS ONE BUT (as usual). If we say that DOT3 is poured into the most perfect "brake" DOT5.1, then the final mixture will turn out to be underestimated. That is, the temperature threshold will fall to lower level. And now we think that the fifth generation "5.1" - IS EXPENSIVE, "3" - IS MUCH CHEAPER. Who in their right mind would mix them up?
It's rather emergency measure, let's say you left for another city, the caliper leaked, you restored it, but your DOT5.1 was not there, you can pour DOT4, but upon arrival it is advisable to replace everything with desired level. After all, the manufacturer did not just flood the fifth generation, which means there were reasons for this, for example, powerful or heavy car, when braking great effort to stop it, respectively, a large warm-up.
SILICONES - DOT5 and ABS they CANNOT be filled with other classes DOT3, DOT4, DOT5.1 - THEY DO NOT MIX! Glycol and silicone are not the same formulations! EVEN DOT5 and DOT5.1 / ABS are not recommended for mixing, although they have the same base, but various characteristics and properties.
Mix from different manufacturers
Well, and lastly, is it possible to mix different manufacturers? YES OF COURSE YOU CAN, why not? After all, there is RIGID standardization, so DOT4 is completely various companies interchangeable, because they must have the same basis and temperature characteristics.
The liquid is not compressible. This law is known to us high school, and it is on it that the operation of the brake system of a modern car is based. What happens if there are exceptions to the law? You say it doesn't happen. Sometimes the owner of the car creates them with his own hands, violating the frequency of replacing the brake fluid. Consider typical faults, which may arise due to its untimely replacement and non-compliance with the rules for performing this operation.
Why change brake fluid? She works in enclosed space, and its properties cannot be changed.
Brake fluid works in a space that can be called closed rather conditionally. The system has compensation holes that let air into it when you press the pedal, and release it when it is reversed. As a result, the brake fluid, which contains, among other substances, various alcohols, absorbs moisture from the surrounding air (the brake fluid is hygroscopic). In addition, irreversible chemical reactions take place in it, and the additives that make up the brake fluid lose their properties over time. Therefore, its composition changes over time, and quite significantly.
Modern brake fluids can be mixed in any proportion.
Indeed, brake fluids can be mixed, but not all and not with all! Only those of them that meet the same standards are mixed. But it should be noted that liquids from different manufacturers, as a rule, have different additive formulations, and sometimes they are made on a different basis. In addition, you cannot always be sure of the brand of fluid poured into the brake system. Therefore, it is still better not to mix brake fluids, as if they are incompatible, the brakes may fail.
IN modern cars any brake fluid that meets DOT-4 standards can be used.
This is a misconception. A number of car manufacturers allow the use of specially designed fluids in brake systems. Some of them are based on mineral basis, so it is strictly forbidden to mix them with glycol fluids. The use of glycol fluids in the brake systems of vehicles designed for mineral water is also unacceptable. Leading manufacturers of brake fluids usually warn consumers directly about this.
Therefore, be sure to follow the requirements of the car manufacturer, and carefully read the description of a particular fluid that you want to purchase. It usually lists restrictions on the use of the product, if any.
Even if the brake fluid absorbs water, it is also incompressible. Therefore, there will be no harm.
In this situation, the problem is not that the water can compress. Since the boiling point of water is only 100C, the more it is in the brake fluid, the lower the boiling point. If we take into account that the braking mechanisms become very hot during braking, such a cocktail can boil, vapor locks form in the liquid and the brakes become weak. In other words, the pedal goes to the floor!. Considering that this phenomenon occurs precisely when it is necessary to slow down strongly and often, the danger is obvious. That is why you should strictly adhere to the recommendations for the frequency of replacing the brake fluid.
The liquid darkens due to the fact that it contains detergent additives, so a change in color is not a sign that a replacement is needed.
Unfortunately, this statement is only true for engine oils. In brake fluids, discoloration is a sign of contamination with wear products and dust particles. If the liquid is not changed for a very long time, other irreversible changes occur in it, it becomes viscous and more like diluted bitumen. Dirt particles can cause the brake cylinders to seize and cause brake failure. There are also frequent cases of the appearance of various varnish-like deposits on the inner surfaces of parts of the brake system. Therefore, the darkened liquid must be changed without waiting for the expiration of the established period.
If you change the brake fluid on time, air cannot appear in the system.
The fluid must be changed not only in a timely manner, but also correctly. There is such an operation - pumping the brake system. In the process of pumping the brakes, the old brake fluid is replaced with a new one, without air entering. To pump the brakes, you will need a small supply of fluid, so you need to buy it about one and a half times more than the capacity of the system. A sign of air entering the system is a feeling soft pedal(the brakes are taken from the second or third time). And you need to pump the system until the pedal becomes stiff and stops at the same point in its travel. When performing this operation, it is necessary to follow the recommendations of the vehicle manufacturer, turning Special attention on the sequence of pumping the brake cylinders, since the completeness of removing air from the brake system depends on it.
The type of brake fluid does not affect the speed of the car, so you can fill in any modern fluid.
Brake fluid, of course, does not affect speed, but the speed characteristics of a car may require a different fluid. When moving to high speeds or with frequent braking, brake fluid with a high boiling point is required. Therefore, a number of vehicles require special liquids. For example, Ford and Rover Group recommend fluids with a boiling point of 260°C for factory filling of the brake system. An example of such a product is Texaco Universal Brake Fluid DOT 4, which specifically states the boiling point value and compliance with the requirements of the above manufacturers. And Texaco Brake Fluid HD, which complies with ISO 4925, FMVSS 116 - DOT 3, 4 and 5.1, SAE J 1703, simply states that it has a high boiling point, both dry and wet. .
Summarize
Use only those brake fluids recommended by the vehicle manufacturer. When purchasing brake fluid, carefully follow the exact specifications for your car, be careful about the recommendations of strangers. Follow recommended fluid change intervals. When buying a used car, it is better to change the brake fluid immediately. You will know exactly what was filled and when. This will avoid guessing whether or not you need to replace it, and avoid problems with the brake system. After changing the fluid, do not forget to bleed the brake system in accordance with the regulations.
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Is it possible to pour tormazuha into a diesel?
| Sonya | March 10, 2017, 22:40:43 |
| Dima327 | September 4, 2018, 05:16:49 PM |
it's dumb to drive with an empty tank, it's better to call a tow truck ...
Dynamics of fluids in the brake system of a car
You rush down a long straight, press the brake pedal, but what should happen does not happen, the pedal sluggishly falls to the floor, and the car flies out of control around the corner ... Moments and in best case the car will need repairs, at worst ... I don’t even want to talk. The only question I want to ask the poor fellow who survived a similar ending: When was the last time you changed the brake?
The hydraulic line filled with brake fluid is essential element, an intermediary between your leg and brake pads, and, as a rule, she does her job perfectly. With the "civilian" use of the car, the brake fluid does not lose its properties for several years.
It is a completely different matter when used at more intense speeds. Fans of driving from traffic lights to traffic lights or car owners who have the opportunity to use their iron horses on the track must remember a few important nuances. Modern brake fluid, no matter how high-quality it is, has its vulnerabilities.
Why does brake fluid boil?
Firstly, chemical composition brake fluid changes when overheated under the influence of numerous intense braking. If it is not changed in time, the properties of the liquid will deteriorate many times over and it will no longer be able to perform its important functions.
Also, the liquid is hygroscopic, which means its ability to absorb water vapor from the atmosphere. Water lowers the boiling point of a liquid. Boiling liquid releases gas. If gas bubbles appear in the brake lines, you will lose the brakes, the pedal will go to the floor.
The lifespan of brake fluid depends on what you ride, how you ride, and even where you ride. Powerful, heavy in a hot and humid climate on the track, it can doom the brakes for one race weekend. Whereas MX-5, in dry and cool weather conditions can last much longer. In street racing conditions, the situation is not much better. How many stories have been written about overheated brakes on heavy and powerful sedans, and it's good if these stories did not end tragically.
Each time after riding, refill new brake fluid, pumping the brakes, of course, the brand, and even a visual check expansion tank will lead nowhere, there may not be bubbles, air may accumulate in other parts of the brake system.
How to prevent brake fluid from boiling?
Your car and your driving style will tell you what to fill in. brake line. Standard DOT 3 or 4 is fine for most normal calm drivers. If you test your brakes by pulling the car back high speed to zero, you should look for a liquid with a higher boiling point, such as ATE Typ 200 (190 ° C) or Castrol React SRF Racing (270 ° C). The liquids are really good, but there are a couple of nuances, they are not easy to get in Russia, you may have to order from abroad and they are not cheap at all. Castrol, for example, will cost $78, about 6,000 rubles.
IMPORTANT! Some brake fluids must not be mixed! Example - DOT 5, having a high boiling point, this type of brake fluid should not be mixed with brake fluids that are less resistant to overheating.
Outcome: Top up with good quality brake fluid extreme conditions use, you can avoid unforeseen situations with failed brakes. Carefully study the instructions for use and technical documentation before switching to a more resistant brake fluid, some types of DOT must NOT be mixed! Also those. documentation will help you decide on the intensity of changing the brake fluid.
Do not use liquid from an already opened bottle, remember about its hygroscopicity.
AND . After the driver, this is perhaps one of the most important systems throughout the car.
GENERAL INFORMATION
When you press the brake pedal, the force through hydraulic drive is transmitted to the wheel (working) brake mechanisms that 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 producers operate under various specifications.
brake fluids various classes mainly apply:
- DOT 3 - for relatively low-speed 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 the road sports cars where the thermal loads on the brakes are much higher.
Note. DOT 5 fluids on conventional vehicles are practically not applied.
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, and 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 basic 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.
Glycolic, based on polyglycols and their esters - groups 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, are efficient 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 - by 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, and in brake mechanisms No. 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, practically does not improve the situation, since a significant part of its volume remains unchanged.
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 by one of the following two methods.
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 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. Before starting the operation, a drain hose must be put on each valve, lowering its other end into a suitable container - escaping brake fluid can damage tires and paint coatings 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 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.
From this article you will learn - why do we need brake fluid for a car, its properties. We will tell you when to change and which one to fill.
The function of the brake fluid is to carry out the work of the hydraulic drive, i.e. transfer pressure from the master brake cylinder (subordinate to the brake pedal) to the wheel brake cylinders, which will brake the movement with the help of shoes. But imagine what could happen if these functions were not performed well enough and the car slowed down much later?
No, it's better not to imagine SUCH ... Why is the quality of the brake fluid so important and what should it be? Understanding...
Requirements
- Work in a wide temperature range: -30 to +150 ( working temperature V brake cylinders during heavy braking).
- Non-aggressiveness: both to rubber sealing parts of the hydraulic system, and to metals;
- High lubricating properties - for the inner surfaces of brake cylinders;
- Stability of properties: their independence from operating conditions.
1. Mineral. It is characterized by low aggressiveness to rubber, good lubricating properties and low price. Disadvantages: very viscous at temperatures below -20, low boiling point. It is widely used only on older machines due to its neutrality to rubber gaskets, it is not used in modern ones.
2. Synthetic from a mixture of polyglycols and ethers. The most common base with high operational properties. Main disadvantage- high hygroscopicity - i.e. ability to absorb moisture, which significantly worsens the main parameters of the brake fluid and causes corrosion of the metal parts of the hydraulic drive.
3. Synthetic silicone. The most modern and completely non-hygroscopic. It is used in rare cases due to poor compatibility with standard rubber parts, complete incompatibility with the previous two types, increased requirements for the quality of pumping for complete removal air from the system, high prices.
Basic properties
Boiling Point: The higher the better. When a liquid boils, vapor is released from it, which, unlike a liquid, is compressed. In practice, this will lead to "failure" of the pedal and lack of braking. It manifests itself with frequent braking, when the heat from friction does not have time to be removed from the brake system and general temperature grows in it (for example, when descending from high mountain in summer). Really dangerous and unpredictable phenomenon.Viscosity stability at low and high temperatures Oh. Critical cases - complete thickening at low temperatures or high fluidity at elevated temperatures (lack of lubrication, likelihood of leakage). In standards, it is measured from +100 and -40.
How often to change?
Brake fluid absorbs moisture from the air and condensation due to constantly changing operating temperatures. This leads to its thickening in winter, poor lubrication in summer and constant corrosion of the metal of the hydraulic system. And the worst thing is that only 3% of the water dissolved in it will reduce the temperature of its boiling by about 70 degrees! This main reason that it is recommended to change it every 2-3 years.For example, for 3 years of operation of the machine, an average of about 3.5 percent of water accumulates in the "brake". When compared with “dry” without water, the boiling point decreases from the standard 250 degrees to 160-180 ° C. The difference is huge. A diluted liquid boils before a "dry" one. In real operation, the brake pedal becomes a stake, but the car does not slow down.
During operation, the brake fluid may change color. Because of high heat, corrosion, oxidation, interaction with rubber parts. Color change does not affect operation. It is difficult to objectively check the condition, the liquid in the system practically does not mix. Accordingly, it will have more water in the tank, and in the working cylinders, due to the constant exposure to high temperatures, its properties will be different.
By the way, for this reason, the addition of a fresh “brake” will have practically no effect on the properties of the system as a whole.
What should be filled in? The most important rule: use the manufacturer's requirements, because. they designed the braking system to specific parameters. The manual also specifies replacement intervals. For example, buy DOT fluids 5.1 or DOT 6 is not needed if you do not know if it is compatible. If you don’t know what was previously filled in, it’s better to completely replace the “brake”.
- What to do if you need to bleed the brakes without an assistant?
How to top up? You need to know what is in the tank under the hood. We buy the appropriate one and top it up. You should monitor the level so that it is at the level of the “max” mark. If it has dropped to the “min” level, then you should definitely top it up. As a rule, top up with working system brakes should be done no more than once a year.
How much to replace? Usually brake system contains not a large amount of "brake". You can clarify in the instruction manual, which indicates the total volume in the system. For complete replacement you need about a liter.
