Cougar/XR7 V8-4.6L VIN W (1997)
Brake Master Cylinder: Initial Inspection and Diagnostic Overview
Bypass Conditions
1. Check fluid in brake master cylinder. Fill brake master cylinder reservoir if low. If fluid is extremely low or empty, check for leaks, or excessive
pad wear.
2. Observe fluid level in brake master cylinder reservoir, note level.
3. "START" vehicle. Apply brakes several times. Shut off engine.
4. If, after several brake applications the fluid level remained the same, measure wheel turning torque required to rotate wheels with brakes applied as
follows:
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Place transmission in "NEUTRAL" and raise and support vehicle.
^
Apply brakes slowly to a minimum of 445 N (100 lbs) and hold for approximately 15 seconds.
^
With brakes still applied, exert torque on one front wheel and one rear wheel to 101 Nm (75 ft. lbs.).
^
If either wheel rotates, the brake master cylinder is bypassing. Overhaul and replace damaged parts.
Normal/Abnormal Conditions
NORMAL CONDITIONS
Usually the first and strongest indicator of anything wrong in the brake system is a feeling through the brake pedal. The following conditions are
considered normal and are not indications the brake master cylinder is in need of service:
A Momentary Or Slight Squirt - of brake fluid within the brake master cylinder reservoir upon application of the brake pedal; this condition is
caused by fluid displacement through the brake master cylinder reservoir compensating port as the brake master cylinder pistons move forward in
the bore when the brakes are applied.
A Slight Turbulence - in the brake master cylinder reservoir fluid occurring 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 - exists on booster shell below the brake master cylinder mounting flange. This condition results from the lubricating
action of the master cylinder wiping seal.
Low Fluid Level Detected - without signs of leakage; this condition is caused by displacement of fluid from the brake master cylinder reservoir
into the disc brake calipers to compensate for normal brake wear. Add the specified fluid as needed.
NOTE: Prior to performing any diagnosis, make sure the brake system warning indicator is functional.
ABNORMAL CONDITIONS
The diagnosis procedures and techniques use brake pedal feel, the warning indicator illumination, and 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 service.
Brake Pedal Goes Down Fast - This could be caused by an external or internal leak.
Brake Pedal Eases Down Slowly - This could be caused by an external or internal leak.
Brake Pedal Is Low Or Feels Spongy - This condition may be caused by no fluid in the brake master cylinder reservoir, reservoir cap vent holes
clogged, rear brakes out of adjustment or air in the hydraulic system.
Brake Pedal Effort Is Excessive - This may be caused by a bind or obstruction in brake pedal linkage or insufficient power brake booster
vacuum.
Rear Brakes Lock Up - during light brake pedal force. This may be caused by wrong tire pressure grease or fluid on linings, damaged linings,
improperly adjusted parking brakes or damaged/contaminated brake pressure control valve.
Brake Pedal Effort Is Erratic - This condition could be caused by power brake booster malfunction extreme caliper piston knock back or
improperly installed disc brake shoe and lining.
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.
Prelininary Inspection -- Start Here
1. When a low brake pedal or the feel of a bottomed-out condition exists, check for brake pedal reserve.
2. Check the fluid level. If the fluid level is below the MAX line in the brake master cylinder reservoir, add the required amount of the specified
fluid.
3. Verify the parking brake control stroke is five to seven notches when pulled with a force of 98 N (22 lbs). If not, refer to Parking Brake -
Adjustments. See: Parking Brake System/Adjustments
4. When in the brake master cylinder area, check the brake tubes and brake master cylinder mounting. The brake tubes and attaching nuts must be
