Every car driver who places safety above everything else, should know how to carry out brake bleeding. If you do not want to face the nightmarish situation of a brake failure, it is absolutely essential that you know this procedure and implement it periodically. Here, I talk about the standard procedure for hydraulic systems.
About the Procedure
Modern cars are equipped with hydraulic braking systems that are controlled by fluid pressure. Bleeding a brake is getting rid of air bubbles that have entered or gotten trapped inside brake lines (that hold hydraulic fluid), which cause a substantial decrease in efficiency.
Normally, hydraulic fluid, which is packed inside brake lines (due to its incompressible nature), leads to the development and maintenance of adequate amount of pressure required for braking. Presence of air bubbles (due to their compressible nature) reduces hydraulic pressure on brakes, thereby reducing braking efficiency of the whole system. That is why, it's necessary that the lines are bled once in a while and the brake fluid is replaced.
How it's Done
In this article, generic instructions for bleeding are provided. Going into specific instructions is not possible, as there may be certain differences in the braking system design of different cars. Consider this to be a rough guide, as you may need to consider some modifications, depending on your car model. Read the maintenance manual, before executing the procedure. Brake fluid, used in modern hydraulic brakes can be toxic and must be handled very carefully.
Tools and Supplies
Car repair and maintenance jobs cannot be executed without proper tools and supplies at hand. Here are the things you'll need:
- Clear Plastic Tubing
- One Box Wrench (should fit the bleeder bolt)
- Turkey Baster (to suck out fluid)
- A Dry and Clear Plastic Bottle
- 28 oz. or 793.772 gm of Brake Fluid
- Spacer (A Small Piece of Lumber)
- Another Human Being (Capable of following instructions, to the word.)
Jack the car up so that the car wheels are about six inches off the ground. Locate the braking system behind every wheel and the bleeder valves. Firstly, you must locate the master cylinder reservoir of the wheel, whose braking system, you plan to bleed. To remove and suck out the brake fluid, with the help of a turkey blaster, you need to remove the top of the master cylinder. Suck out as much of old braking fluid as possible, with the help of the turkey blaster. Make sure that you do not spill the braking fluid anywhere, as it can be corrosive. Clean up the insides of the master cylinder with an old (preferably lint-free) piece of cloth.
After that draining and mop up job, get the new braking fluid and pour it inside the master cylinder, before replacing the cylinder top. Ask your buddy to seat himself in the driver's seat and pump the brake pedal at least fifteen times or more. This will get the fluid to fill in the brake lines. Keep a spacer (piece of lumber) between the brake pedal and the floor to prevent total grounding of the pedal.
Now you need to set up things for the actual job. Get hold of the box wrench and locate the bleeder bolt on the braking system. Just loosen the bleeder valves, with the help of a box wrench. Do not open the valves fully. Only loosening them slightly is recommended.
Get that dry clear bottle and pour some brake fluid in it (about one or two inches). Get the clear plastic tubing and dip its one end, inside the bottled fluid, and push the other end over the bleeder bolt for draining fluid.
Once you have set up the bottle, remove the cylinder top again, pour fresh braking fluid inside the master cylinder and make it full. Close the top and ask your buddy to press down slowly on the brake pedal. Keep it depressed until you tell him to stop. Once he confirms that the pedal has been depressed completely, turn the bleeder bolt by one quarter with the help of a box wrench. As soon as you turn it, the fluid will flow down the tube and into the bleeder bottle.
Make sure that the other end of tube is dipped inside the fluid or air will enter back in. After all the fluid is drained, close the bleeder valve again by turning the bolt in reverse. Once the valve is closed, ask your buddy to remove his leg from the pedal and let it go up.
Repeat the entire process until the fresh clear fluid that you poured in, starts coming out of the tube and you notice bubbles coming out. The master reservoir cylinder should never be left without fluid, as that will let the air enter into the braking system.
After a sufficient number of such flushing iterations, air will be taken out of the brake lines. Once the clear fluid, along with bubbles (air), gets drained, you can tighten the bleeder bolt and take out the tube. The process for one wheel is done. Next, you must repeat the same process with the rest of the three wheels.
Fill the reservoir, pump down the pedal and hold, loosen the bleeder valve, let the fluid and air bleed, close the valve and let go of pedal. That is the process in a nutshell, which you will repeat for the rest of the wheels. Start with the wheel which has the longest brake line and go in the descending order. (The recommended order is right rear wheel, left rear wheel, right front wheel and left front wheel.)
Some Tips and Warnings
When it comes to bleeding anti-lock braking systems, I will advise you to take help from a professional, as they require a scanning tool. Make sure that you use the manufacturer recommended braking fluid to fill the reservoir. Using the wrong type of fluid can lead to total brake system failure. In case you are not confident about the entire procedure, take help from a professional for the first time and see how it's done.
The braking system of a car is something that has to be functioning properly. Without fully-operational brakes, driving is very hazardous. There can be no compromises when it comes to maintenance, unless your car can fly. So ignoring car problems, especially those related to braking, is not recommended.