The requirements for brake fluid are quite serious - it should not accumulate water (condensate from the air) in itself, and also have a stable viscosity in the range from -60 to +300 degrees. The brake fluid should be neutral to cuffs, rubber bands and metal.
With prolonged or sharp braking, a very strong heating of the brake pads occurs, and this heat is transferred to the caliper piston, thereby the brake fluid can boil, forming vapor plugs in the system, which makes the brake pedal wadded or falls through, and for effective braking, you have to pump up pressure by rapid pressing the brake pedal. This problem is especially common on Gazelles, since the vehicle's braking system is not designed for the weight they are carrying.
Brakes, like engine oils, are different, but they are united by the Dot3 or Dot4 model.
Dot 3 - quite old brake fluid and the only plus, the cost is slightly lower than Dot4 and it can be mixed with DOT4. This fluid can be used in vehicles in which the braking system is not loaded. Replacing such a fluid every 2 years.
Modern cars in our climatic zone use DOT4 and Dot 3 is no longer on sale. More advanced than DOT3, it has several advantages. Increased boiling point, the composition contains additives that absorb moisture and, accordingly, such a liquid freezes less at low temperatures. The cost of 1 liter is about 300 rubles. Replacement of brake fluid DOT4 every 3 years.
Liquid DOT5 they are not used in our climate, since the composition includes silicone, which simply does not mix with water, and condensate that accumulates in some depression simply freezes and blocks the passage of liquid along the line. DOT5 does not mix with DOT4 or DOT3.
Why you need to change the brake fluid.
Condensation gets into any liquid in the car and the brake is no exception. Water reduces the property of the brake fluid, it begins to freeze, boil and such fluid becomes aggressive to metal, forming corrosion on the cylinders or pistons of the calipers. Severe corrosion of the caliper causes brake fluid to leak. Motorists, who save on timely replacement of brake fluid, pay doubly in the future to replace parts of the brake system, and this is at best.
How to change brake fluid
A brake fluid change can be combined with a seasonal wheel change. You will need an 8 or 10 wrench and a short 5mm tube and a liter of Dot4. In order not to break the lines the pumping nozzle, the connection points are treated with penetrating grease and then we unscrew the socket head with a tight fit, as they unscrewed, you can also drain with an open-end wrench
It is enough to pump out the old liquid from the tank with a syringe and fill in a new one. Then, at the far wheel, unscrew the bleed fitting and drain the liquid about 30 milliliters and so on for each wheel. The last one should be the wheel that is closest to the brake fluid reservoir.
Volume brake fluid reservoir 0.5-0.8 liters, depending on the car brand.
If the brake fluid is leaking - in fact, there is nothing to worry about, as the brake pads wear out and the brake calipers move out more and the fluid level decreases. When installing new pads, the level will return to normal. As a rule, when the brake level is low, the parking brake lamp flashes.
Replacing the brake fluid by replacement
Some car owners believe that a simple replacement of the brake with replacement takes place, since the fluids mix and the brake will gradually push out all the water, but this is not the case. Water is heavier than brake fluid and if it is already present in the tank, then there is even more of it in the brake caliper and it can only be displaced by a complete replacement, unscrew the bleed fitting and drained. Otherwise, the liquid does not change.
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Brake fluid is a type of hydraulic fluid that is used in hydraulic brake systems and hydraulic clutch systems on cars, motorcycles, light trucks, and bicycles. The fluid is used to transmit pressure and to enhance the braking force.
General information about brake fluid
The principle of operation of the brake fluid is its low compressibility. Molecules do not have internal voids, therefore, when compressed, the volume of the liquid does not decrease, and the pressure quickly spreads to the entire volume.
Brake fluid composition
There are different types of brake fluid, but it is usually made from a low-viscosity solvent such as alcohol and a viscous non-volatile substance such as glycerin.
On the basis of polyethylene glycol, brake fluid is produced under the brands DOT 3, DOT 4 and DOT 5.1.
Silicone-based - silicone-organic polymer products DOT 5 grade.
For vehicles with anti-lock braking system, DOT 5.1 / ABS braking fluids based on silicone and glycols can be used. About brake fluids wiki: link.
Characteristics and properties of brake fluid
In order for the braking system to function 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 ambient 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, since in this case moisture evaporates from the fluid in the form of vapor. And steam is dangerous in that it is easily compressed and during the next braking the pressure on the brakes will be less, since part of the volume will be taken away by the compressed steam.
The boiling point of brake fluid directly depends on 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 brands of "brake" have minimal hygroscopicity (moisture absorption), for example, DOT 5 and can maintain the required characteristics throughout the 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 is pumped throughout the system will depend on this characteristic. And it should pump well both at -30 degrees Celsius and at 200 degrees during braking.
If the fluid freezes completely or in places, it will block the brakes. Too thick fluid will be difficult to pump throughout the system, which will lead to either poor braking or different effort on different wheels. And too liquid will lead to leaks.
Corrosion protection... The brake fluid itself acts as a corrosion protection inside the brake system. In this case, protection must be provided even with small amounts of moisture inside the system.
Corrosion protection is ensured 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:
- you can only add liquid with a higher rating figure, that is, DOT 4 can be poured into DOT 4, 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.
- Mineral (eg LHM +) and glycolic fluids must not be mixed.
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 mileage. These are general guidelines.
If the car is operated in harsh conditions, then it is necessary to 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, and anti-corrosion additives work worse. You can use the refilling method only when carrying out repairs or in the event of a leak, when you just need to drive to the service station or garage.
You can determine an unusable brake fluid:
- With a complete analysis using special equipment.
- "By eye" - the old liquid is dark in color, while the new one is translucent.
- Using a device that determines 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 into the expansion tank of the brake system. It is usually located above the brake master cylinder and serves to compensate for brake fluid when it heats up and to prevent air from entering the system.
The fluid level in the reservoir should 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 a specialized service station. Most modern cars have an ABS system, and this leaves its mark on the procedure. Special equipment is required for pumping the system with new fluid.
If you are told that you can perform a brake fluid change without bleeding without special equipment, then do not listen to these tips. Yes, on some wheels the pressure from the reservoir can push the system through, but this will not work on all. 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 average brake fluid volume is 0.75 to 1.3 liters.
A clear change of brake fluid without special equipment is described in the video below:
Brake fluid prices
Usually 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 and should be kept away from open flames and high temperatures.
In no case should you drink, even a small amount will lead to poisoning. If liquid comes into contact with eyes, rinse thoroughly with clean water and consult a doctor.
You already know the main features of brake fluid. You know that this liquid must remain dry, must not boil and freeze. In the second part, we will look at each of the main parameters in detail.
Boiling
Typically, the boiling point is measured separately for "dry" and "wet" liquids. This is done in order to be able to build a temperature graph for the entire period of possible operation of the fluid. For the dough, only 3.5% water is added to the liquid, but this is enough to project the absorption of water from the air. When heating and cooling a liquid, its viscosity is measured, as a rule, an average temperature range from -40 to +100 degrees Celsius is taken for measurements. During this period, almost all modern standards fit: FMVSS No. 116, ISO 4925, SAE J 1703 etc. In real conditions, the working temperature of the TJ can reach the limits from -50 to 150 degrees Celsius.
How will the liquid boil noticeably?
During heating and subsequent boiling, gas bubbles will begin to form in the TZ. Part of the liquid will be squeezed out into the reservoir of the master brake cylinder and gas will take its place. A gas lock will appear in the system. Whoever has pumped the brakes knows what it looks like to the driver. The brake pedal becomes soft and moves effortlessly. The car naturally does not react to your actions and continues to drive as before.
Why does brake fluid boil?
Laziness, forgetfulness, water. Water throughout the rest of the text will be the main enemy, albeit indirectly relative to human folly.
Most cars only have 1000ml of fluid in their brakes. By adding 2% water to it, and this is not much less than 20 ml by volume, we will lower the boiling point by 70 degrees. If we take, for example, DOT-4, then it will boil at 150-160 degrees. You can trust me. In the city you will not notice this, but emergency braking on the highway ... sorry, there are no guarantees. It’s good if it’s winter and TJ freezes. In this case, you can find out about the problem in advance. The viscosity of the fluid will rise sharply and it will be extremely difficult for you to wait until the brakes are applied.
Is the brake fluid frozen?
The reason is the same - water. Not a timely replacement. “I haven't changed it for five years and everything is fine” is an unnecessary and inappropriate philosophy.
But that's not all. The rather harsh operating conditions of the TJ, its inevitable aging, leads to the fact that the components of the liquid begin to oxidize, while releasing not the most quiet compounds. Shells and dents on the working surfaces of the elements of the brake system are not traces of any mechanical action, but the results of chemical reactions. Oxidation products of tAs perfectly corrode metals. Moreover, the longest reaction test is only 120 hours at 100 degrees Celsius. So, under certain conditions, not even a year will pass before the car will require repair - expensive repairs.
After all of the above, you can probably not mention that water is rust, but, nevertheless, it is a fact.
How to avoid problems?
Yes, by and large it is easy. The cost of servicing the braking system is acceptable in the vast majority of cases. I deliberately do not write any prices, because times go by, prices change, and in this matter the problems are the same as 30 years ago.
The operating rules are simple.
If you don't know something about the braking system of your car, change the fluid immediately after buying a car. Then repeat this every couple of years. Under normal conditions, more frequent replacement is not required.
Driving through puddles, etc. Through the cylinders of the brake system, water will not penetrate into the liquid, unless of course you park at night on the rapids in the water. The main affected area is the tank and its lid. As we saw in the first part, there is a hole in the lid. Although it is not large, it is not designed for high pressure washing.
What else can speed up fluid change. Damp areas of operation, large temperature differences, which will inevitably cause the formation of condensation on the walls and lid of the tank. Some issues need to be approached individually.
How to assess the condition of the brake fluid?
Yes, no how! Not. It is clear that it should be clean, transparent and without sediment ... but in most cases the tank itself will not allow you to find out, and even if you find it as such, it will not say anything about how much water it has already absorbed. Good people have made an analyzer instrument with which you can find out everything about the condition of the TJ, but the cost of the device is such that not only does it make no sense to buy it for personal use, but sometimes it will be cheaper to change the liquid than to pay the cost of such a test at the station. Although if offered for a small price, agree, it will definitely not be superfluous.
Features.
It is only possible to mix brake fluid within a class, for example DOT-4.
DOT-4 and DOT-5 must not be mixed.
Adding fluid to the system. Let's do it this way. It makes sense to add liquid to the system only if it starts to go away on the road and you just need to get home. If the liquid leaves, then you need to look for the cause at the first opportunity, because the brakes fail instantly, you can't guess anything.
Top up - refresh. It's not an option at all. TG does not restore its properties when adding fresh liquid. In this case, it is nothing more than a waste of money.
Store liquid only in a sealed container. No air, no temperature difference, no moisture. With its assortment and cost, it is easier not to store. So. Buy on the road just in case, but it's not worth carrying in the trunk all the time.
If you decide to work with TJ on your own, there are a few things you need to keep in mind.
Do not smoke while working with liquid. Forbidden. Dangerous.
TJ is poisonous. It is practically the most dangerous liquid in a car. She is also aggressive. In case of contact with eyes, rinse with plenty of water and immediately seek medical attention without delay.
If the TJ has been swallowed. Induce vomiting immediately, by any means, and immediately go to the nearest hospital. The fact that the legends say that it was drunk during Prohibition will not give you a chance. There is a complex cooking method... In order to endanger the life of an adult, 100 milliliters of liquid is enough. Moreover, it is under threat with resuscitation and all the like.
From the subtleties.
When working with elements of brake systems, cuffs, anthers, seals - do not wash them with gasoline and kerosene. These rubber bands are made of pure rubber and cannot withstand such washing without consequences.
In conclusion, I would like to touch upon one more point.
There is no standard for the production of brake fluids in Russia. There is only a set of technical conditions, applying which everyone does what he wants. Well, or what happens. I do not recommend using domestic fluids in foreign systems. The statistics that come from experience are not comforting. Foreign cars are leaking on our brakes.
When no fluid leaks in the hydraulic brake drive, it would seem that you do not need to pay attention to it. However, braking efficiency and system stability depend on its state. If, for example, poor antifreeze or engine oil only shortens the life of the engine, then poor quality brake fluid can lead to an accident.
General information
Brake fluid (TB) consists of a base (its share is 93-98%) and various additives (the remaining 7-2%).
Obsolete liquids, for example "BSK", are made on a mixture of castor oil and butyl alcohol in a 1: 1 ratio. The basis of modern, most common, including domestic ("Neva", "Tom" and RosDOT, aka "Rosa"), are polyglycols and their ethers one . Much less commonly used silicones 2 .
In the complex of additives, some of them prevent the oxidation of TF by atmospheric oxygen and under strong heating, while others protect metal parts of hydraulic systems from corrosion.
Basic properties any brake fluid depends on the combination of its components.
- Boiling temperature. The higher it is, the less likely a vapor lock will form in the system. When the vehicle is braking, the working cylinders and the fluid in them heat up. If the temperature exceeds the permissible value, the TZ will boil and vapor bubbles will form. The incompressible fluid will become "soft", the pedal will "fail" and the machine will not stop in time.
- The faster the car went, the more heat will be generated during braking. And the more intensive the deceleration, the less time will be left for cooling the wheel cylinders and feed pipes. This is typical for frequent prolonged braking, for example in mountainous areas and even on a flat highway, loaded with traffic, with a sharp "sporty" driving style.
The sudden boiling of TZ is insidious in that the driver cannot predict this moment.
- Viscosity characterizes the ability of the fluid to be pumped through the system. The temperature of the environment and the TZ itself can be from minus 40 ° C in winter in an unheated garage (or on the street) to 100 ° C in the summer in the engine compartment (in the master cylinder and its reservoir), and even up to 200 ° C with intensive deceleration of the car ( in the working cylinders). Under these conditions, the change in the viscosity of the fluid must correspond to the flow sections and clearances in the parts and nodes of the hydraulic system specified by the vehicle designers.
Frozen (all or in some places) TJ can block the operation of the system, thick - it will be difficult to pump through it, increasing the brake response time. And too liquid - increases the likelihood of leaks.
- Impact on rubber parts. Seals should not swell in TZ, reduce their size (shrink), lose elasticity and strength more than is permissible.
Swollen cuffs make it difficult for the pistons to move back in the cylinders, so the vehicle may slow down. With seated seals, the system will be leaky due to leaks, and deceleration will be ineffective (when the pedal is depressed, the fluid flows inside the master cylinder, not transferring force to the brake pads).
- Impact on metals... Parts made of steel, cast iron and aluminum should not corrode in the TJ. Otherwise, the pistons will "sour" or the cuffs working on the damaged surface will quickly wear out, and the fluid will flow out of the cylinders or will be pumped inside them. In any case, the hydraulic drive stops working.
- Lubricating properties. For the cylinders, pistons and cuffs of the system to wear less, the brake fluid must lubricate their working surfaces. Scratches on the mirror of the cylinders provoke TJ leaks.
- Stability - resistance to high temperatures and oxidation by atmospheric oxygen, which occurs faster in a heated liquid. The oxidation products of tAs corrode metals.
- Hygroscopicity - the tendency of polyglycol-based brake fluids to absorb water from the atmosphere. In operation - mainly through the expansion hole in the tank lid.
The more water is dissolved in the TH, the earlier it boils, thickens more strongly at low temperatures, lubricates parts worse, and the metals in it corrode faster.
Brake fluid classes
In Russia, there is no single state or industry standard regulating the quality indicators of brake fluids. Domestic manufacturers work according to their own specifications, focusing on the norms adopted in the USA and Western Europe (standards 3 J1703, ISO (DIN) 4925 and FM VSS N116). Liquids are classified according to boiling point and viscosity, the rest of their properties are similar.
What TJ should be used in a car is decided by its manufacturer. As a rule, fluids of class DOT 3 are intended for relatively slow-moving machines with all drum brakes or disc brakes in front. TZh with improved performance characteristics, corresponding to the requirements of DOT 4, are designed for modern cars with increased dynamic qualities. Such cars allow frequent sharp accelerations and intensive decelerations, and they have predominantly disc brakes on all wheels. Liquids of the DOT 5 class are rarely used, mainly on road sports cars. Thermal loads on TJ are comparable to those arising in the hydraulic systems of special racing cars.
Liquids "BSK" and "Neva" (grades A and B) do not meet modern requirements for boiling points, and "BSK" also does not meet low-temperature properties. It freezes already at minus 20 ° C.
Features of the operation of brake fluids
The absorption of water from the atmosphere is characteristic of polyglycol-based TA. At the same time, their boiling point decreases. FM VSS standardizes it only for "dry", not yet absorbed moisture, and humid, containing 3.5% water, liquids - ie. limits only limit values. The intensity of the absorption process is not regulated. TG can be saturated with moisture at first actively, and then more slowly. Or vice versa. But even if the boiling point values \u200b\u200bfor "dry" liquids of different classes are made close, for example, to DOT 5, when they are moistened this parameter will return to the level characteristic of each class. However, in laboratory tests, TG manufacturers, as a rule, build curves of the boiling point change. They are different for each liquid.
TG needs to be periodically replaced, without waiting for its condition to approach a dangerous limit. The service life of the fluid is assigned by the car plant, having checked its characteristics in relation to the features of the hydraulic systems of its cars.
Checking the condition of the liquid. It is possible to objectively determine the main parameters of TAs only in the laboratory. In operation - only indirectly and not all.
The liquid is independently checked visually - in appearance. It should be transparent, homogeneous, without sediment. In addition, in car services (mainly large, well-equipped, servicing foreign cars), its boiling point is assessed with special indicators. Since the liquid does not circulate in the system, its properties may differ in the tank (test location) and in the wheel cylinders. In the reservoir, it comes into contact with the atmosphere, gaining moisture, but not in the brakes. On the other hand, the liquid there often and strongly heats up, and its stability deteriorates.
However, even such tentative checks should not be neglected, there are no other operational control methods.
Compatibility. TAs with different bases are incompatible with each other, they stratify, sometimes a precipitate appears. The parameters of this mixture will be lower than that of any of the original fluids, and its effect on rubber parts is unpredictable.
The manufacturer, as a rule, indicates the basis of TJ on the packaging. Russian RosDOT, Neva, Tom, as well as other domestic and imported polyglycolic liquids DOT 3, DOT 4 and DOT 5.1, can be mixed in any proportion. TJ class DOT 5 are based on silicone and are incompatible with other 4. Therefore, FM VSS 116 requires "silicone" fluids to be dyed dark red. The rest of modern TJs are usually yellow (shades from light yellow to light brown).
For additional verification, you can mix liquids in a 1: 1 ratio in a glass container. If the mixture is clear and there is no sediment, the TAs are compatible.
Replacement. The addition of fresh fluid during pumping of the system after repair does not restore the properties of the TJ, since almost half of it practically does not change. Therefore, within the time frame set by the car plant, the fluid in the hydraulic system must be completely replaced. The sequence and features of this operation, for example, bleeding with the engine running, depend on the design of the system (such as an amplifier, anti-lock brakes, etc.) and are known to specialists of service stations. Often this information is in the vehicle manual.
On domestic cars, the fluid is replaced in one of the following two ways.
- The old TJ is completely drained by opening all the air release valves (fittings) and draining the system. Then the tank is filled with fresh liquid and pumped in by pressing the pedal. The valves are sequentially closed when TZ appears from them. Then air is removed from each circuit (branch) of the hydraulic drive.
- The disadvantage of this technique is the need for final (control) pumping of the system. In addition, a discharge hose must be put on each valve by lowering its other end into a suitable container5 - the leaking TJ can damage tires and paint on suspension parts, brakes, wheels. But the new liquid is guaranteed not to mix with the old one, and part of the fresh TZ released during pumping, having allowed it to settle to remove air and filtered, can be used again.
- The replaceable TJ is displaced with fresh, constantly refilling it into the tank of the master cylinder and preventing the system from draining. For this, each circuit is pumped in turn until fresh liquid appears from the valve.
- In this case, air does not enter the hydraulic drive, but it is possible that some of the old TJ will remain in it, since it is difficult for an inexperienced person to distinguish it from a new one. In addition, more fluid is needed than when pumping in the previous way. Part of it released from the system is mixed with the old and unusable.
Safety measures when working with TJ
You need to store any liquid only in a hermetically sealed container so that it does not come into contact with air, does not oxidize and does not absorb moisture from it or evaporate.
A WARNING
In hydraulic systems, rubber seals based on natural and synthetic rubber are used. The latter can withstand high temperatures well, but such rubber is destroyed by mineral oils, gasoline and kerosene. Therefore, when repairing system components, flush or lubricate the cuffs, and even metal parts, you only need fresh clean brake fluid.
- Brake fluids "Neva", "Tom" and RosDOT are flammable, and "BSK" is flammable. It is prohibited to smoke while working with them.
- TG is poisonous - even 100 cm3 of it, if it gets inside the body (some liquids smell like alcohol and can be mistaken for an alcoholic drink), can lead to the death of a person. In the case of ingestion of TJ, for example, when trying to pump out part of it from the reservoir of the master cylinder, you must immediately induce vomiting (see our help). If liquid gets into eyes, rinse with water jet. And in any case, consult a doctor.
OUR REFERENCE
You can induce vomiting by drinking (optional):
- as much water as the body will accept (usually 2-2.5 liters);
- 3-4 glasses of soapy water;
- a glass of warm water in which a teaspoon of dry mustard is diluted.
- You need to choose a TJ recommended by the car factory.
- Liquid packaging must be airtight. When lightly squeezed from the sides, it springs.
- The membrane under the lid is preferable from foil - this does not allow water to pass through and indicates the reliability of the manufacturer.
The editors would like to thank Ph.D. E. M. Vizhankova and senior researcher GI Matrosov, specialists of the 25th State Research Institute of the Ministry of Defense of Russia, for their help in preparing the material.
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1 Polyglycols and their ethers are a group of chemical compounds based on polyhydric alcohols. They have a high boiling point and good low temperature properties.
2 Silicon-organic polymer products. Their viscosity depends little on temperature, they are inert to various materials, they are efficient in the temperature range from minus 100 to 350 ° С.
3 SAE - Society of Automotive Engineers (USA), ISO (DIN) - International Organization for Standardization, FM VSS - Safety Precautions Act (USA).
4 Liquids of class DOT 5.1, which do not contain silicone, are sometimes referred to as DOT 5.1 NSBBF, and silicone DOT 5 - DOT 5 SBBF. The abbreviation NSBBF stands for "non silicon based brake fluids" and SBBF stands for "silicon based brake fluids".
5 The same should be done when removing air from the system or its circuit. In addition to damage to parts, fluid escaping from the valve under pressure can splash into the eyes.
Based on site materials www.zr.ru
Before filling the brake system with fluid, it is necessary to thoroughly clean the master cylinder and bypass valves on the wheel cylinders of the brakes and the hydraulic vacuum booster from dirt, check and adjust the clearances between the pusher and the piston of the master cylinder, as well as between the pads and brake drums.
The brake system only needs to be filled with special brake fluid. Mixing of different brands of brake fluids is not allowed. It is strictly forbidden to add to the system even in the smallest amounts mineral oils, gasoline, kerosene or mixtures that cause destruction of rubber parts of the brake system.
How to pour alcohol into the brake system
In the absence of a special brake fluid, a mixture consisting of 50% (by weight) castor oil and 50% butyl alcohol can be poured into the system. Butyl alcohol can be replaced with isobutyl or ethyl alcohol, but keep in mind that ethyl alcohol evaporates more easily and the composition of the mixture can change quickly, especially in hot weather or with prolonged use of the brakes.
You cannot replace castor oil with glycerin, since its viscosity increases greatly with decreasing temperature.
If a different type of brake fluid is poured into the system, then it is necessary to remove the old fluid from it and thoroughly flush the entire brake system with alcohol, acetone or new fluid. When pouring brake fluid into the system, the maximum cleanliness must be observed, since if dirt enters the system, the brakes fail.
To fill the system and remove air from it, proceed as follows:
- Unscrew the filler plug of the master cylinder and fill the cylinder with brake fluid.
- Remove the rubber protective cap of the bypass valve of the wheel cylinder of the right rear brake and replace it with a rubber hose, the other end of which is placed in the brake fluid, poured halfway into a glass vessel with a capacity of at least 0.5 liters.
- Unscrew the bypass valve by 1/2 ... 1/4 turn, then press the brake pedal several times. Press the pedal quickly and release slowly. In this case, the liquid from the master cylinder fills the system and displaces air from it, which exits through the bypass valve, the hose and through the liquid into the vessel in the form of bubbles. During pumping, it is necessary to add fluid to the master cylinder, preventing the bottom from being exposed in its reservoir.
- After the exit of air from the system stops (the bubbles from the hose lowered into the glass vessel will stop), it is necessary to tightly screw the bypass valve with the pedal depressed, remove the hose from the bypass valve and put on a protective cap.
- Bleed the brake system in the same way in the following sequence: front right brake, front left brake, rear left brake, hydraulic booster cylinder (through two bypass valves).
- After bleeding the brake system, add fluid to the master cylinder so that its level is 15-20 mm below the upper edge of the filler hole, and tighten the master cylinder plug tightly.
Before installing the plug, blow air through the vent hole.
If all brakes and actuator are correctly adjusted and there is no air in the system, then the brake pedal should not be depressed more than half the stroke when pressed, after which the pedal should feel "hard". Lowering the pedal more than half the stroke indicates large gaps between the brake pads and drums.
If the resistance of the pedal is insignificant, it can be squeezed almost to the stop on the floor of the cab (“soft” pedal), this indicates that there is air in the system. In this case, it is necessary to continue pumping until the air is completely removed.
Do not press the brake pedal if at least one drum is removed, since the pistons will be squeezed out of the wheel cylinder under the fluid pressure and the fluid will flow out.
The fluid used to bleed the brakes can be reused, allowing it to settle until air bubbles are removed.
Bleeding the system must be carried out not only when the brake system is filled with fluid, but also when disconnecting any part of the hydraulic system for repair or replacement, i.e. when air can somehow enter the system.
