Car Brake fluid

How to understand that it's time to change the brake fluid

To check the brake fluid efficiency, consult the service station specialists. They will measure its boiling point and the water percentage in its composition with the help of a special tester.

You may identify that you need to estimate the brake fluid quality by the following signs:

• insufficient brake pedal resistance to pressing;
• decreased braking efficiency;
• car pulling to one side;
• change of the fluid color.

Causes why the brake fluid prematurely loses its service properties

Brake fluid operates in high temperature conditions. At the moment of braking it heats up to an average of 200°C, but can sustain even higher values: from 205°C to 265°C. Since the fluid is hygroscopic, eventually the water percentage in its composition significantly increases, which causes it to boil much earlier than usual. This results in air inleakage and even a complete brakes breakdown. Increase in the water amount by only 2-3% lowers the boiling point by 30-50°C.

Premature loss of the fluid service properties may occur due to unsatisfactory brake lines condition. Rubber hoses have a porous structure. If the micropores size is increased, for instance, under the impact of direct sunlight, or when microcracks appear because of ingress of thawing chemicals, the hoses can no longer provide the proper tightness of the system.

The more water in the brake fluid, the higher is the risk of the unit components corrosion. Their wear products form deposits on the internal surfaces of the components, which can cause the pistons and cylinders to jam.

Often the necessity for the brake fluid early replacement occurs due to its non-compliance with the vehicle specifications or a driving style. In particular, products with a higher boiling point are used in sports cars, but the additives included in them can increase the aeration risk. These fluids are not suitable for vehicles equipped with the ABS system.

In some cases low braking efficiency is caused by the combined use of consumables different in composition. Their ingredients can react chemically, which not only results in deterioration of the fluid performance characteristics, but also leads to destruction of the system sealing and connecting components.

Replacement of brake fluid

The brake fluid replacement in vehicles equipped with integral ABS is best to be entrusted to specialists. In other cases you can fill the brake system on your own. At the same time, it is very significant not to confuse the order of bleeding the mechanisms which is specified in the car technical documents. Adhere to the following procedure:

1. Mount the vehicle on a lift, a pit or a ramp. You can use a jack to unload the required sides of the vehicle one after another.
2. Dismantle the wheels.
3. Remove dirt from the surfaces of the wheel cylinder bleeding valves.
4. Unscrew the expansion tank cap and fill it to the maximum level.
5. Connect the transparent hose to the valve connector, and immerse its second end into a container partially filled with brake fluid.
6. Ask your assistant to press the brake pedal a few times and hold it in this position, and unscrew the bleed valve at the same time.
7. Check the tank for fluid level: the amount of fluid should not be lower the minimum mark.
8. Repeat the procedure a few times until a clean fluid without bubbles flows out from the hose.
9. Disconnect the hose, wipe the valve dry and install a protective cap on it.
10. Repeat the procedure with all brake mechanisms.