Changing brake fluid is a mandatory vehicle maintenance procedure. Must be done at regular intervals. It involves the complete removal of all old brake fluid and filling with new one. Many neglect this type of service, which often ends in serious trouble. The easiest way to change the brake fluid is to contact a specialist. However, this procedure is easy to do on your own. There are several ways. There are also special devices that allow one person to service the brake system of a car.
Why change brake fluid?
Brake fluid is a type of technical fluid used in hydraulic brake systems to transfer force from the pedal to the pads. For its production, glycol ethers are used, as well as mineral oils and silicone. Compositions based on the last component are practically not saturated with water, due to which the service life is slightly extended and the frequency of replacement is increased. Mineral liquids are practically not used today, although they are cheaper than others. Glycolic brake fluids are the most common.
For any type of brake fluid, the following five parameters are important:
- Boiling point.
- Anti-corrosion properties.
Let's dwell on this for a bit.
The brake fluid must be free of foreign particles and inclusions. It should not be cloudy and inexpressive in color. A good liquid is transparent, has a uniform beautiful color. Cleanliness is important so that nothing gets into the brake calipers, in which pistons that are precisely fitted to them move. To evaluate the appearance of the fluid, look into the expansion tank of the brake system.
For brake fluid to perform its function, its viscosity must be stable over a wide temperature range. The brake system can vary from -30°C to +200°C. This parameter is especially important for cars with installed anti-lock braking system ABS.
When braking, the fluid gets very hot, but should not boil. When this happens, vapor locks form and the efficiency of the system drops dramatically. The reason is very simple. The gas is easily compressed and compacted, the force from the pedal to the pads is transmitted worse, or does not reach at all. The boiling point of the brake fluid decreases over time by itself, as water constantly accumulates in the system. Even though it's sealed. As a result, braking efficiency is also reduced.
Parts of the brake system, especially the pistons in the calipers, are made of metal with microscopic precision, and therefore the slightest rust threatens to jam the mechanism and pinch the pads. Corrosion is provoked by water, which in the brake fluid should not be more than 3.5%. Also, special anti-corrosion additives are added to some fluids, which extends the life of both the fluid itself and the system parts. Over time, they lose their protective properties.
The principle of operation of the hydraulic brake system is based on the ability of fluids not to decrease in volume with increasing pressure. However, this ability may be impaired by critical temperatures. Water in the brake fluid reduces its boiling point, which increases the risk of vapor lock and a sharp decrease in braking performance.
The gradual deterioration of all these parameters is the reason why the brake fluid must be regularly changed to fresh. If this is neglected for a long time, which many do, then over time the braking will become less and less effective. Later, such negligence will end up in nasty brake failure, pad jamming, or premature repairs. All this is much more expensive than a couple of bottles of new brake fluid and 1...3 hours spent on replacement. Yes, even at the service station, a replacement will cost ten times cheaper than just one new caliper.
How often do you need to change the brake fluid in your car?
The frequency of replacement is always indicated in the car's owner's manual, but also depends on a number of factors:
- liquid quality;
- composition and class;
- driving style;
- state of the brake system;
- type and class of car.
If we consider the example of an ordinary car driven by a non-aggressive driver, often does not carry a trailer and does not move along mountain serpentines, it is recommended to change the brake fluid:
- once every 2…4 years;
- every 30...50 thousand kilometers;
- after a major overhaul of the brake system;
- after two years of parking;
- if the liquid is cloudy, dirty, of an incomprehensible color;
- with a water content of more than 3.5%.
The percentage of water content is determined using a special tester. It is not very expensive and extremely easy to use. The working part of the tester is immersed in the brake fluid in the expansion tank, and its serviceability is determined by the indication. If you use high-quality synthetic brake fluid, which is changed every two years, then it is not necessary to buy a tester.
How to choose brake fluid?
When choosing a brake fluid to replace, be guided by the recommendations of the manufacturer of your car. If there is no information, then choose according to the following principle:
- DOT 3 is a car without ABS , drum brakes are installed at the rear and disc brakes at the front.
- DOT 4 is a car with ABS and disc brakes.
- DOT 5 and 5.1 are sports cars and special vehicles that operate in extreme temperature conditions.
Mixing different brake fluids is not recommended. Although there is nothing wrong with that.
How much brake fluid does it take to change?
The brake system has the smallest volume in a car. Even if the car is large, the brake fluid in it is no more than 0.5...0.9 liters. Additionally, this information is recommended to be clarified in the manual for the repair and maintenance of a particular vehicle. When choosing and buying a liquid, the volume of the system must be multiplied by 2. The stock will be needed for a better displacement of the old liquid. Also useful if you accidentally spill some of the liquid on the ground. Later, the stock can be used to bleed the brake system.
Safe handling of brake fluid
Brake fluid is extremely fluid, penetrating everywhere, and an extremely poisonous thing. With careless handling, it is quite possible to end up in intensive care with serious poisoning. To prevent this from happening, when changing the brake fluid, follow these simple safety rules:
- perform replacement either outdoors or in a well-ventilated area;
- wear safety goggles;
- do not neglect rubber gloves;
- do not smoke;
- don't drink;
- do not eat;
- in case of contact with the skin or eyes, rinse under running water for 10 minutes;
- do not allow liquid to come into contact with the vehicle's paintwork and plastic parts.
Please do not pour used brake fluid into sewers, natural water bodies or simply on the ground. Where to put her? In large cities, there are enterprises that accept waste fluids for processing. Find them on the Internet, pack the liquid in glass containers and recycle it.
How to change brake fluid?
There are several ways. Here are three that are suitable for home use. Get a helper to make your job easier. You will also need some tools that you can make yourself or buy in a store. Tools: jack; wrench to remove wheels; wrench for fittings on calipers.
Sequential brake fluid replacement
This is the most correct way to change the brake fluid. You will need: a large medical syringe; homemade device for collecting old fluid and bleeding the system. To assemble such a device, take a transparent 1 liter bottle and a transparent flexible tube.
Why is this method called sequential replacement? You will serve each circuit in turn according to the scheme. The scheme depends on the configuration of the brake system. For example, if the car is left-hand drive, and the main brake cylinder with an expansion tank is on the left, then the rear right circuit will be serviced first. Then the front left, rear left and front right. That is, first the furthest from the main brake cylinder, then the pair to it, and then the remaining ones according to the same principle.
Algorithm for sequential replacement of brake fluid:
- Stop the engine.
- Wait for the brakes to cool down.
- Unscrew the cap of the expansion tank and pump out the liquid (with a syringe).
- Fill the tank with new fluid (as much as you like).
- Raise the primary wheel and remove it.
- Lower the jack a little so that the car is level.
- Put a tube on the caliper fitting.
- Pour some brake fluid into the bottle.
- Lower the tube into the bottle so that it is immersed in the liquid (it should remain in this position until the end of the procedure).
- Give a signal to the assistant to “pump” the brake pedal (he should press it two or three times, and then lock it in the pressed position, continuing to press on it with effort.
- When the assistant gives a signal that the pedal has rested, unscrew the fitting (old liquid will flow into the container.
- When the assistant gives a signal that the pedal has almost reached the floor, screw the fitting back.
- Repeat steps 9-10-11 until new brake fluid flows through the tube without air bubbles.
- Before each pumping, check the fluid level in the expansion tank.
- Repeat steps 4-5-6-7-8-9-10-11-12-13 for all circuits according to the scheme.
- Before servicing the fourth circuit, do not fill too much liquid into the expansion tank.
After changing the brake fluid, start the engine and pump the brake pedal several times. It should “be solid” almost at the very beginning of the turn. If the pedal fails, then there is air in the system. You need to re-bleed the brakes. When driving for the first time, carefully check the operation of the brake system. If there are no brakes or they are “weak”, pump it. There is air left.
Parallel brake fluid change
This way is easier. But he has his shortcomings. There is a chance that air will remain in the brake system, which can only be completely removed over time. The second disadvantage is that in order to change the brake fluid, you must lift the car completely and remove all the wheels. It is difficult to do this at home.
- Stop the engine.
- Unscrew the cap from the expansion tank of the brake system.
- Pump out the old fluid.
- Empty all circuits (use a homemade device from a bottle and a tube).
- Screw all fittings back to their original position.
- Fill the expansion tank with new fluid.
- Pump all circuits according to the standard scheme.
Be aware that air may remain in the system. If the brake pedal fails, then it's there. Reboot the system. In some cases this may not be required. It all depends on how you filled and pumped fluid when replacing. The less rushed, the greater the chance of success.
Replacing the brake fluid with a special tool
To change the brake fluid without an assistant, you can use a special tool.
- container for automatic topping up of brake fluid in the expansion tank;
- a container for collecting old fluid with a pneumatic mechanism;
- transparent tubes;
- adapters and fittings.
It costs $40 and up. If you want to buy a cheap model, pay attention to the pipes - they can be of disgusting quality.
Algorithm for replacing brake fluid with a device:
- Open expansion tank.
- Suck out the old fluid (with a syringe).
- Attach a container to the expansion tank for automatic replenishment of the level (previously pour new brake fluid into it).
- Jack up the first side.
- Remove the wheel.
- Connect a container for collecting old fluid with a pneumatic system and a tube to the caliper fitting.
- Unscrew the fitting.
- Pull the trigger of the tool and pump out the brake fluid from the circuit until new fluid without air appears in the tube.
- Repeat for all circuits according to the diagram.
- Remove tools and add brake fluid to the MAX level .
Carefully check the function of the brakes.
VIDEO: changing brake fluid
Changing brake fluid is as important as changing engine oil. Although performed much less frequently. Ideally, brake fluid should be changed every two years or every 30 thousand kilometers. Choose the brand and class of fluid in accordance with the recommendations of the manufacturer of your car. Or focus on the configuration of the brake system. After replacement, always test the brakes in a safe place with the utmost care.