Brake Fluid Flush

All the car braking systems of today are hydraulic type, which control braking action through fluid pressure. The periodic changing of brake fluid, is a largely ignored braking system maintenance chore, due to the little or no mention, it gets in automobile manuals.

Why is it Important?
The primary reason for a periodic brake fluid replacement is the chemical nature of the glycol based braking fluids. These chemicals are hygroscopic, that is they have a tendency to absorb moisture. With moisture absorption, boiling point of these fluids goes down and the efficiency of braking also gets compromised. When the boiling point drops, the brakes don't work properly in high temperature conditions or high braking situations. Fresh fluid is clear, while the one which has absorbed moisture is denser and less clear. This deterioration of braking fluid quality can be especially detrimental to anti-lock braking systems.

There is no way that one can totally stop the entry of moisture into the braking system, as the whole system is exposed to atmosphere through venting. During each opening of the master cylinder, a little moisture is absorbed. However, the process of absorption is slow and if you schedule a regular fluid flush, then this problem of brake fading, due to moisture absorption can be kept at bay. Brake flushing guarantees that your brakes have a shorter response time and they work perfectly when you need them.

Choice of Fluid
It is important that you replace old fluid with right type of new fluid. Brake fluids are classified into three main types, which are DOT 3 (lower boiling point temperature threshold is 400 Degree Fahrenheit) DOT 4 (lower boiling point temperature threshold is 450 Degree Fahrenheit) and DOT 5.1 (lower boiling point temperature threshold is 500 Degree Fahrenheit). The DOT 5.1 are used mostly in racing cars. Check what is the kind of fluid used before and replace it with the same kind of fluid. Make sure that new fluid can is sealed until you are ready to use it.

Procedure
The procedure is similar to the technique of bleeding brakes. The things you'll need for the procedure are a plastic tubing, box wrench, turkey baster, a clear plastic bottle and new fluid. You will also need another person to help you out. Wear hand gloves and safety glasses.

To gain access to the brake mechanism underneath, use a jack. Use two jacks, as they can effectively support the elevated vehicle. You must carry out the brake flushing exercise for one wheel brake at a time. First part of fluid flushing is opening the master cylinder and draining the fluid using a turkey baster. Then clean the insides thoroughly and make sure that no contaminants are left inside.

Pour the new fluid inside the master cylinder and top it up. Ask somebody to sit in the driver's sat and wait for your instructions. Locate the bleeder valve in the braking system. Attach a clear plastic tubing to the bleeder valve and dip its other end in to a clear bottle, partially filled with the braking fluid. Ask your helper to press down slowly on the brake pedal, without flooring it. Once he has pressed it down, open the bleeder valve by quarter turn and drain braking fluid. Then close the valve and ask your helper to release brake pedal. Repeat the process until clear fluid starts streaming out of the master cylinder. At periodic intervals, replenish the master cylinder with the fluid. Repeat the procedure on rest of the wheel braking systems. That is brake fluid flushing for you in a nutshell. Nowadays, specially designed flushing tools and machines are available that can carry out the job even easily.