Focus L4-2.0L SOHC VIN P (2000)
Brake Master Cylinder: Testing and Inspection
General Procedures
Usually, the first and strongest indicator of anything wrong in the brake system is a feeling through the brake pedal. In diagnosing the condition of the
brake master cylinder, check pedal feel as evidence of a brake concern.
Check for brake warning indicator illumination and the brake fluid level in the brake master cylinder reservoir.
Normal Conditions
The following conditions are considered normal and are not indications that the brake master cylinder is in need of repair.
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New brake systems are not designed to product as hard a pedal effort as in the past. Complaints of light pedal efforts should be compared to pedal
efforts of another vehicle, same model and year.
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During normal operation of the brake master cylinder, the fluid level in the reservoir will rise during brake application and fall during release. The
net fluid level (after brake application and release) will remain unchanged.
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A trace of brake fluid exists on the brake booster shell below the master cylinder mounting flange. This results from the normal lubricating action
of the master cylinder bore end seal.
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Fluid level will fall with brake shoe wear.
Abnormal conditions
NOTE: Before carrying out any diagnosis, make sure the brake system warning indicator is functional.
Changes in brake pedal feel or travel are indicators that something could be wrong in the brake system. The diagnostic procedure and techniques are
brake pedal feel, warning indicator illumination and low brake fluid level as indicators in diagnosing brake system concerns. The following conditions
are considered abnormal and indicate that the brake master cylinder is in need of repair.
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Brake pedal goes down fast. This could be caused by an external or internal leak.
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Brake pedal eases down slowly. This could be caused by an external or internal leak.
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Brake pedal is low feels spongy. This condition may be caused by no fluid in the brake master cylinder reservoir, reservoir cap vent holes clogged
or air in the hydraulic system.
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Brake pedal effort is excessive. This may be caused by a bind or obstruction in pedal/linkage, clogged fluid control valve or insufficient booster
vacuum.
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Rear brakes lock up during light pedal force. This may be caused by grease or fluid on brake shoes, damaged brake shoes and linings, incorrectly
adjusted parking brakes, or damaged/contaminated brake pressure control valve.
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Brake pedal effort is erratic. This condition could be caused by brake booster inoperative, extreme caliper piston knock back or incorrectly
installed brake shoes and linings.
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Brake warning indicator is ON. This may be caused by low fluid level, ignition wire routing too close to fluid level indicator assembly, or float
assembly damage.
