Sable V6-183 3.0L DOHC VIN S MFI (1997)
Brake Master Cylinder: Initial Inspection and Diagnostic Overview
Abnormal Conditions
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Changes in brake pedal feel or travel are indicators that something could be wrong in the brake system. The diagnostic procedures and techniques
use brake pedal feel, warning indicator illumination and low brake fluid level as indicators in diagnosing brake system concerns.
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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 or 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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Pedal effort 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 brake lockup during light pedal force. This may be caused by wrong tire pressure, grease or fluid on rear brake shoes and linings, damaged
rear brake shoes and linings, improperly adjusted parking brakes or damaged or contaminated brake pressure control valves.
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Erratic pedal effort. This condition could be caused by power brake booster malfunction, extreme caliper piston knock back or improperly
installed brake shoes and linings.
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Brake warning indicator "ON". This may be caused by low fluid level, ignition wire routing too close to fluid level indicator assembly, float
assembly damage, or binding parking brake.
Normal Conditions
The following conditions are considered normal and are not indications that the brake master cylinder is in need of service.
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During normal operation of the brake master cylinder, the fluid level in the brake Master Cylinder 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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Low fluid level 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 fluid as needed. If very low, check for worn brake pads or shoes.
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A trace of brake fluid existing on the booster shell below the master cylinder mounting flange is normal. This results from the normal lubricating
action of the master cylinder bore end seal.
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A trace of brake fluid found on the outside of the power brake booster below the brake master cylinder mounting flange. This condition results
from the lubricating action of the master cylinder wiping seal.
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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 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.
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A Slight turbulence in the brake master cylinder reservoir fluid when the brake pedal is released. Turbulence occurs as brake fluid returns to the
brake master cylinder after releasing the brakes.
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New brake systems are not designed to produce as hard a pedal effort as in the past. Complaints of light pedal efforts should be compared to pedal
efforts on another vehicle of the same model and year.
Prelininary Inspection -- Start Here
NOTE: Always check the fluid level in the brake master cylinder before performing the test procedures.
NOTE: It is possible that all evidence of fluid leakage may have washed off if the vehicle has been operated in rain or snow because brake fluid is
water-soluble. Refill system, bleed and apply the brakes several times. Examine the system to verify that the reservoir fluid level is actually dropping.
Locate and correct the external leak. If fluid level drops and no external leak can be found, check for a brake master cylinder bore end seal leak.
CAUTION: Use of any other than the approved DOT-3 brake fluid will cause permanent damage to brake components and will render the brakes
inoperative.
PRE-CHECKS
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Fill brake master cylinder with specified brake fluid to between MAX line and 4.0 mm (0.16inch) below line on reservoir. Use High Performance
DOT-3 Motor Vehicle Brake Fluid meeting Ford specifications.
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Usually, the first and strongest indicator of a problem 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.
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Check for brake warning indicator illumination and the brake fluid level in the brake master cylinder reservoir.
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Inspect the brake master cylinder mounting nuts. Tighten brake master cylinder nuts to 23 Nm (17 ft. lbs.).
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The brake tube nuts must not show signs of leakage. Tighten brake tube nuts to 16-20 Nm (12-14 ft. lbs.).
Master Cylinder Internal Inspection
