Brake fluid is the lifeblood of arguably the most important system in your car: the brake system. Without it, the brakes are useless. for it is the brake fluid which enables the hydraulic pressure that stops the car when the brake pedal is pressed. Occasionally, brake fluid begins to run low and needs to be refilled. You can locate the car’s brake master cylinder underneath the hood towards the firewall in front of the driver’s side. There should be a line indicating the full level. If it is lower than this, but fluid is still visible. Simply pop off the cap and pour in new brake fluid up to the line. If, however, there is no fluid visible, the process becomes a bit more complicated.
If the brake fluid has receded out of sight, it means you will have to bleed the brakes. You cannot simply pour in fluid now because air has potentially gathered in the brake lines. This air must be removed. First, fill the master cylinder with brake fluid up to the line. Have a helper sit in the driver’s seat. You have to go to each wheel and locate the wheel cylinder to bleed each of them of air.
Go to the farthest wheel from the master cylinder first. This is usually the rear passenger tire. Climb under the car with your flashlight, small wrench or socket set and bleeder kit. Locate the wheel cylinder valve. It will look like a small nozzle with a sealed hole in the center. Attach either a small wrench that fits or the right size socket and loosen the valve.
Once loose, attach the plastic hose of the bleeder kit to it and lead the other end into the glass or plastic jar. Tell the helper to pump the brakes.
You will see a combination of brake fluid and air come into the jar. Pump the brakes until the bubbles stop–this means no more air. Once that happens, instruct the helper to hold the pedal down and don’t let up. Remove the hose and retighten the valve. They can let up on the brakes now.
The next farthest wheel cylinder is the driver rear side. Repeat the process. Loosen the valve, attach the hose, have the assistant pump the brakes until only brake fluid comes into the jar. Hold the brakes down, remove the hose and retighten the valve.
You will likely have to refill the master cylinder at least once in this process to ensure that there is always fluid in the lines. Don’t try to bleed the brakes without fluid in the lines or you will have to do it all over again.
The second to last wheel cylinder to bleed belongs on the front passenger tire. Repeat steps 2 through 4.
The last is the front driver wheel cylinder. Once you have repeated the steps, it is time to refill the master cylinder for the last time. Fill the master cylinder again up to the mark.
At this point, all four wheel cylinders have been bled. There should be next to no air in the brake lines, and the master cylinder is full. The brakes should not be mushy, nor should the pedal go to the floor.