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Maintenance Guide - All about brake fluid and its maintenance.

Snapshot: The article extensively covers everything that you need to know about brake oil maintenance procedure like replacement and refill etc. The different grades of brake oils such as DOT 3, DOT 4, DOT 5 and DOT 5.1. correspond to their boiling points and temperature range within which they would work.

Automobile braking systems depend on hydraulics and lubricating fluids called brake oils to function properly. Brake oils have evolved over the time greatly to ensure better and smooth functioning. There are different types of brake oils including grades such as DOT 3, DOT 4, DOT 5 and DOT 5.1. All these various types of brake oil correspond according to their boiling points as they work in very high temperature as well as pressure environments. The DOT 3 and DOT 4 brake oils are the most commonly used in India as well as globally.

The boiling points of the brake oil require being high to avoid vaporization, as vapor can hinder the efficiency of a hydraulic system. Vapor can also result in pressure differences which can lead to the rupturing of the brake lines. 
Brake oils absorb moisture from atmosphere the DOT 3, DOT 4 and DOT 5.1 are able to absorb water up to a certain extent in normal humidity levels. DOT 5 is silicon based oil and is fully water repellent. DOT 5 brake oil is thus not compatible with anti-lock braking systems. DOT 5 brake oil which is silicone based has additives that deter water retention and keep the oil from becoming sludgy in low temperatures, and is ideal for very cold climates. 

Steps to refill brake fluid

Things you will need: Brake fluid recommended by the car manufacturer, Gloves and Funnel

It's essential that the brake fluid is refilled every time before it drops below the 'Min' or 'Low' level mark because running the master cylinder dry can cause brake to fail. 

1. Open the engine hood and locate the brake fluid reservoir. Generally, the brake oil reservoir is located beside the engine firewall, at the back of the engine bay and close to the driver’s side. The brake oil reservoir is also usually located higher up in the engine bay for easy accessibility.   

2. Most modern cars come with see through brake fluid reservoir that let one to check the level of the brake fluid without opening the cap. The markings (Min and Max) on the brake fluid reservoir indicate the amount of fluid that's present. 

3. Generally, the reservoir cap also has indication printed on it regarding the grade of oil that the brake system is using. Make sure that you use the recommended grade only.  

4. Open the reservoir cap and use a funnel to pour the oil to avoid spill. Brake oil is toxic and hazardous for health and it can also corrode the car paint. Therefore, avoid contact with paint and use gloves during the entire procedure. 

5. Ensure that you close the cap tight to prevent the oil from coming in contact with air. Since most fluids are hydroscopic and absorb water, they can deteriorate on coming in contact with air and can cause brakes to fail.   

Steps for draining and replacing the brake fluid 

Things you will need: Abundant brake fluid, Gloves, Funnel, Car jack, Wheel brace, Bleeding bottle, Frame stands, 100ml syringe and Spanner set

The brake oil must be changed one in every two years as the oils absorb moisture and over the time get saturated. The moisture content can essentially damage the braking system by corroding seals and the metal inside it. Therefore, old brake oil should be flushed out completely and replaced with brand new oil.

Draining and replacing brake fluid is a comparatively more complex task in comparison to refilling. Therefore, before you start this, refer to the manufacturer's service manual and ensure that you have all the tools you would need during the procedure. Also, make sure that you have understood the entire procedure correctly and there's no room for error.

1. Find a solid and flat ground on which you can put the car on stands without any chances of slipping. Put the car on frame stands by successively removing each individual wheel.

2. Open the engine hood and locate the brake fluid reservoir as mentioned above. Open the reservoir cap and remove the old oil from it with the help of a syringe. You would not be able to remove all of it but remove much as you can.

3. Fill the reservoir with new brake fluid and let it go even beyond the 'Max' mark but prevent it from spilling.

4. Subsequently, locate the bleeder valve on each brake calliper, which is generally on the inside end and looks like a nipple and generally has a rubber cap on it. Your car might have drum brakes at rear and disc brakes at front, to find the exact location of the bleeder valves, you can also refer the owner's manual.

​5. The old fluid in the brake lines will be replaced with the new fluid by bleeding the fluid through the bleeder valves located on each individual callipers. Bleeder valves should be bled in a sequence as recommended by the manufacturer, alternatively, you can follow the sequence in the decreasing order of distance from the reservoir. Locate the bleeder valve "Position 1" and open the nut only slightly with a spanner, just 3/4th of a complete turn. Subsequently, open the bleeder screw and connect the bleeding bottle pipe to collect the brake fluid. Have some extra fluid in the bottle and keep the pipe immersed in it at all times this would prevent air from entering into the system from the bleeder valve. 

6. Push the brake pedal repeatedly and do it until the new fluid starts coming out of the tube into the bottle. Without removing the tube, tighten the bleeder screw. Subsequently, remove the rubber tube and replace the rubber cap of the bleeder valve. Ensure that at all times there is sufficient fluid in the brake fluid reservoir and you are never operating the brake pedal without the fluid, since this can cause severe problems. If needed, take help of someone with this.

7. Repeat the steps with other bleeder valves present on each brake calliper.

8. Before finally closing the brake fluid reservoir, make sure that you fill it uptill the 'Max' mark and not any further.

9. Put all wheels back and remove the car from frame stands.        

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