Brake System Test Procedure

An inspection of the brake hydraulic system begins with a brake fluid level check.
1. If the brake fluid level is below the MIN line on the brake master cylinder reservoir, add the required amount of brake fluid. Make sure the brake fluid meets the required specifications.
2. When in the brake master cylinder area, check the brake lines and brake master cylinder mounting. The brake tube flare nuts must be tight. The brake tube flare nuts must not show any signs of leakage. The following conditions are considered normal and are not indications that the brake master cylinder is in need of service:
- Low brake fluid level detected without signs of leakage. This condition is caused by displacement of brake fluid from the brake master cylinder reservoir into the brake calipers to compensate for normal brake shoe and lining wear. Add brake fluid as needed.
- A momentary or slight squirt of brake fluid from the brake master cylinder reservoir upon application of the brake pedal. This condition is caused by brake fluid displacement through the brake master cylinder reservoir compensating port as the master cylinder pistons moves forward in the bore when the brakes are applied.
- Slight turbulence in the reservoir fluid when the brake pedal is released. Turbulence occurs as brake fluid returns to the brake master cylinder after releasing the brakes.
- A trace of brake fluid found on the power brake booster shell below the brake master cylinder mounting flange. This condition results from the lubricating action of the master cylinder wiping seal.

4. Inspect the brake tubes under the vehicle for damage and proper routing. Check the brake hoses connecting the brake tubes to the brake calipers for any signs of damage, cracking or softening. The hose fittings must be tight without signs of leakage.
5. If signs of leakage are not present but the reservoir brake master cylinder reservoir is definitely low, it is possible that evidence of brake fluid leakage may have been washed off by rain or snow because brake fluid is water soluble. To determine if a leak exists, proceed as follows:
a. Refill the system
b. Bleed the system
c. Apply the brakes several times.
d. Examine the system to verify that the brake master cylinder reservoir level is actually dropping.
e. Locate and correct the external leak.

Internal and external leaks are two problems that can affect a brake hydraulic system. The hydraulic brake system will not cause the vehicle to do any of the following:
- Vibrate
- Pull
- Grab
- Squeal
- Allow the brake pedal to pulse

In most cases the hydraulic system will no even cause the brakes to drag. The sources of these problems are found elsewhere in the brake system, but it is always a good policy to first check the entire hydraulic system for leaks before continuing to diagnose any other brake problems.