How to Bleed and Flush a Car Brake System
The brake fluid in your cars brake system is a hydraulic based fluid that is used to transfer force from the brake pedal to the brake caliper or the wheel cylinder. The purpose of the brake system fluid change is remove moisture, air and containment's from the braking system, as well as replacing the fluid that has been broken down by today’s complex Anti-Lock braking systems. Moisture is the leading cause of brake system operation failure. Brake fluid is subject to extreme pressure and heat so the boiling point of brake fluid is important.
Higher boiling points (severe duty) and Anti-Lock braking systems require higher quality brake fluid; this fluid must also have a very low freezing point. There are several forms of brake fluid that are rated by the government for the various boiling points and other factors. These rating are DOT2, DOT3, DOT4 and DOT5. Distinctive ratings define the chemicals the fluid is produced with such as, mineral oil, ester glycol esters and synthetic oils. Many of these fluids are not compatible so make sure you add and flush your brake system with the manufacturers recommended brake fluid. Almost all brake fluid is corrosive and extreme care must be used when handling brake fluid.
Always uses protective gloves, clothing and eyewear to guard against accidental spillage. If any brake fluid is spilled, flush thoroughly with water, this goes for human contact as well as spillage on your car as the fluid will remove paint. Always add brake fluid from a sealed container and never allow moisture into the brake fluid. A brake system flush is used to remove any moisture and dirt out of the system and replace it with new fluid. After a flush is complete a full system bleed procedure is required, always check brake pedal operation after the work is complete, if normal brake pedal operation is not present do NOT move car until further inspection or repairs are performed.
Typical Brake Master Cylinder
Identify brake master cylinder components, brake fluid cap, brake master cylinder, fluid lines, and brake fluid level sensor. Inspect for any brake fluid leakage around the master cylinder and check for proper fluid level regularly. If leakage is present replace master cylinder immediately.
Typical Bleed nipple for cars
1. Bleed nipple with cap 2. Brake pipe
Removing Brake Fluid
Remove brake fluid reservoir cap and insert brake fluid removal tool, remove as much brake fluid as possible, then refill the master cylinder with new fluid. Most cars use DOT3 or DOT4, but you should consult the cap on the master cylinder or a service manual. Once the master cylinder is full loosen all four brake fluid bleeder screws on the brake calipers or wheel cylinders. Next, press the brake pedal down completely, while holding the brake pedal down have a helper close all four brake bleeder screws. Allow the brake pedal to return to normal position slowly, this will draw new fluid into the master cylinder body. Continue this procedure until the brake fluid is clean out of each bleeder, close all bleeders and refill the master cylinder to the proper level.
Bleed using tube and sutable container
Stuck Brake Bleeder - Is the brake bleeder screw tight? Yes very, this is because all bleeder screws seal against a taper fit seat in the brake wheel cylinder or caliper to create the valve that controls brake fluid flow. When loosening a brake bleeder always spray WD40 or equivalent to aid rust removal then use a quality tool with little to no wear on it.
No Fluid out of the Brake Bleeder - This can be because the bleeder is not used very often so it can get filled with dirt and moisture, clogging the passage. If this is the case open the plugged bleeder (with other 3 closed) and press the brake pedal down, this additional pressure from the other bleeders being closed will force the fluid out of the plugged bleeder. Once the bleeder has become unplugged finish the bleeding procedure until clean fluid is present. Then close the bleeder and release the brake pedal slowly.