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Focus 1999 (08.1998-12.2004)

Brake System - General Information - Brake System Focus 1999 (08/1998-12/2004)
Diagnosis and Testing

General Equipment
Pressure/vacuum gauge set
The Ford approved diagnostic tool

The brake system operates by transferring effort applied to the brake pedal by the driver to the brakes at each wheel.

The braking effort is distributed to each wheel, using a hydraulic system. The system is assisted using a vacuum brake booster that reduces pedal effort and increases hydraulic pressure.

The parking brake operates on the rear wheels and is applied using a hand operated control.

Inspection and Verification

NOTE:
NOTE:Before carrying out any diagnosis, make sure that the brake system warning indicator is functional.
  1. Verify the customer concern.
  1. Visually inspect for obvious signs of mechanical or electrical damage.

Visual Inspection Chart

Mechanical Electrical
  • Tire pressure(s)
  • Wheels and tires
  • Fluid leak(s)
  • Brake pipe(s)
  • Electrical connector(s)
  • Wiring harness(s)
  • Switch(es)
  1. If an obvious cause for an observed or reported concern is found, correct the case (if possible) before proceeding to the next step.
  1. If the cause if not visually evident, verify the symptom and refer to the Symptom Chart.

Road Test

Carry out a road test to compare actual vehicle braking performance with the performance standards expected by the driver. The ability of the test driver to make valid comparisons and detect performance deficiencies will depend on experience.

The driver should have a thorough knowledge of the brake system operation and accepted general performance guidelines to make good comparisons and detect performance concerns.

An experienced technician will always establish a route that will be used for all brake diagnosis road tests. The road selected will be reasonably smooth and level. Gravel or bumpy roads are not suitable because the surface does not allow the tires to grip the road equally. Crowned roads should be avoided because of the large amount of weight shifted to the low set of wheels on this type of road. Once the route is established and consistently used, the road surface variable can be eliminated from the test results.

Before a road test, get a complete description of the customer concerns or suspected condition. From the description, the technician will be able to match possible causes with symptoms. Certain components will be identified as possible sources while others will be eliminated by the evidence. More importantly, the customer description can reveal unsafe conditions which should be checked or corrected before a road test. The description will also help form the basic approach to the road test by narrowing the concern to specific components, vehicle speed or conditions.

Begin the road test with a general brake performance check. Using the description of the concern, test the brakes at different vehicle speeds using both light and heavy pedal pressure. Determine if the concern is in the front or rear braking system. First use the foot brake and then the parking brake. If the condition (i.e. pull, vibration, pulsation) occurs only on operation of the parking brake, the concern is in the rear brake system. If the condition occurs when the foot brake is depressed, the concern is in the front brake system.

Avoid locking the brakes and sliding the tires. This condition will not indicate brake efficiency. A heavily braked but turning wheel will stop the vehicle in a shorter distance than locked wheels.

If the concern becomes evident during this check, make sure it fits the description given before the road test. If the concern is not evident, attempt to duplicate the condition using the information from the description.

If a concern exists, use the Brake System Symptom Chart in order to isolate it to a specific sub-system and condition description. From this description, a list of possible sources can be used to further narrow the cause to a specific component or condition.

Symptom Chart

Symptom Possible Sources Action
Brakes pull or drift
*
Worn or damaged brake shoes or brake pads and linings.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-03, Removal and Installation).
*
Abnormal wear or distortion of front brake disc.
*
INSTALL a new front brake disc.
REFER to: Brake Disc (206-03, Removal and Installation).
*
Malfunctioning rear brake shoe adjuster.
*
CHECK the automatic brake shoe adjuster.
*
Incorrectly adjusted parking brake.
*
ADJUST the parking brake cable.
REFER to: Parking Brake Cable Adjustment (206-05, General Procedures).
*
Incorrect wheel alignment adjustment.
*
ADJUST the wheel alignment.
*
Incorrect wheel bearing preload adjustment.
*
INSTALL a new wheel bearing as necessary.
REFER to: Front Wheel Bearing (204-01, Removal and Installation).
*
Grease or fluid on the brake shoes or brake pads; glazed linings.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-03, Removal and Installation).
*
Stuck or seized wheel cylinders or brake calipers.
*
INSTALL a new wheel cylinder or brake caliper.
REFER to: Wheel Cylinder (206-02, Removal and Installation) /
Brake Caliper (206-03, Removal and Installation).
Brake warning indicator is always on
*
Low brake fluid level.
*
FILL the reservoir. CHECK the brake and clutch system for leaks including brake fluid in the brake booster.
*
Leak in the hydraulic system.
*
REPAIR the leak. CHECK the entire hydraulic system. FILL and BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
*
Leaking brake master cylinder primary piston cup.
*
CARRY OUT a brake master cylinder bypass condition test. REFER to Brake Master Cylinder Component Test in this procedure.
*
Parking brake control not fully released.
*
FREE UP and ADJUST the parking brake cable.
REFER to: Parking Brake Cable Adjustment (206-05, General Procedures).
INSTALL new components as necessary.
*
Malfunctioning anti-lock braking system (ABS).
*
REFER to: Anti-Lock Brake System (ABS) Module (206-09A, Removal and Installation) / Anti-Lock Brake System (ABS) Module (206-09A, Removal and Installation).
*
Shorted indicator circuit.
*
REPAIR as necessary.
Vibration when the brakes are applied
*
Grease or fluid on the brake shoes or brake pads; glazed linings.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Worn or damaged brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Loose caliper mounting bolt(s).
*
TIGHTEN the caliper mounting bolt(s).
*
Insufficient grease on sliding parts.
*
APPLY grease where necessary.
*
Damaged brake drum contact surface.
*
INSTALL a new brake drum.
REFER to: Brake Drum (206-02, Removal and Installation).
*
Excessive brake disc thickness variation or brake disc runout.
*
CARRY OUT a brake disc runout check.
REFER to: Brake Disc Runout Check (206-00 Brake System - General Information, General Procedures).
*
Wheels and tires.
*
CHECK the tires. BALANCE or INSTALL new tires as necessary.
*
Loose or missing wheel hub bolts.
*
TIGHTEN or INSTALL new wheel hub bolts as necessary.
*
Worn or damaged brake drums or brake discs.
*
INSTALL new brake drums or brake discs.
REFER to: Brake Pads (206-04, Removal and Installation) /
Brake Shoes (206-02, Removal and Installation).
Pedal goes down fast
*
Low brake fluid level.
*
FILL the reservoir. CHECK the brake and clutch system for leaks including brake fluid in the brake booster.
*
Leak in the hydraulic system.
*
REPAIR the leak. CHECK the entire hydraulic system. FILL and BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
*
Air in the system.
*
CHECK for leaks. BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
*
Brake disc “brake knock back” (Brake pads push the brake caliper piston back into the brake caliper. Caused by excessive brake disc lateral runout or loose wheel bearings.)
*
CARRY OUT a brake disc runout check.
REFER to: Brake Disc Runout Check (206-00 Brake System - General Information, General Procedures).
*
Worn brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Worn brake master cylinder piston cups or scored cylinder bore.
*
GO to Pinpoint Test A.
Pedal eases down slowly
*
Air in the system.
*
BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
*
Malfunctioning brake master cylinder.
*
Low engine vacuum (stationary).
*
GO to Pinpoint Test B.
Pedal is low or feels spongy
*
Worn brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-03, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
GO to Pinpoint Test B.
*
Air in the system.
*
CHECK for leaks. BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
GO to Pinpoint Test B.
Brake lockup during light brake pedal force
*
Glazed or worn brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Brake booster.
*
Low engine vacuum.
*
GO to Pinpoint Test C.
Excessive or erratic pedal travel
*
Worn brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Wheel bearings
*
CARRY OUT brake disc runout check.
REFER to: Brake Disc Runout Check (206-00 Brake System - General Information, General Procedures).
Brake drag
*
Incorrectly adjusted stop lamp switch.
*
ADJUST the stop lamp switch. GO to Pinpoint Test B.
*
Incorrectly adjusted speed control deactivation switch (if equipped).
*
ADJUST the speed control deactivation switch. GO to Pinpoint Test B.
*
Incorrectly adjusted parking brake.
*
ADJUST the parking brake cable.
REFER to: Parking Brake Cable Adjustment (206-05, General Procedures).
GO to Pinpoint Test B.
*
Brake booster.
*
REFER to brake booster operation check in this procedure.
*
Seized brake caliper or wheel cylinder.
*
INSTALL a new brake caliper or wheel cylinder.
REFER to: Wheel Cylinder (206-02, Removal and Installation).
GO to Pinpoint Test B.
*
Seized brake caliper slide pins.
*
INSTALL a new brake caliper.
REFER to: Brake Caliper (206-04, Removal and Installation).
GO to Pinpoint Test B.
*
Seized parking brake cables.
*
INSTALL new parking brake cables. GO to Pinpoint Test B.
Excessive brake pedal effort
*
Worn or contaminated brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Malfunctioning vacuum pump (diesel).
*
INSTALL a new brake vacuum pump.
REFER to: Brake Vacuum Pump (206-07 Power Brake Actuation, Removal and Installation).
*
Disconnected or damaged brake booster vacuum pipe.
*
CONNECT or INSTALL a new brake booster vacuum pipe as necessary.
*
Brake booster.
*
GO to Pinpoint Test D.
Brake noise
*
Worn or damaged brake shoes or brake pads.
*
INSTALL new brake shoes or brake pads.
REFER to: Brake Shoes (206-02, Removal and Installation) /
Brake Pads (206-04, Removal and Installation).
*
Brake booster.
*
GO to Pinpoint Test E.
Slow or incomplete brake pedal return
*
Brake booster.
*
Seized brake pedal pivot.
*
GO to Pinpoint Test F.

Pinpoint Tests

PINPOINT TEST A : PEDAL GOES DOWN FAST
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
A1: PRESSURIZE THE SYSTEM
1
Pump the foot brake rapidly five times.

Does the brake pedal height build up and then hold?
Yes
CHECK parking brake adjustment and ADJUST as necessary.
REFER to: Parking Brake Cable Adjustment (206-05, General Procedures).
If the condition still exists. BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
TEST the system for normal operation.
No
GO to A2.
A2: CHECK FOR BRAKE SYSTEM LEAKS
1
Check for external brake and clutch system leaks. Refer to Brake Master Cylinder Component Test in this procedure.

Are any leaks present?
Yes
REPAIR as necessary. ADD fluid and BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
TEST the system for normal operation.
No
GO to A3.
A3: PERFORM A BRAKE MASTER CYLINDER BYPASS CONDITION TEST
1
Carry out a Brake Master Cylinder Bypass Condition Test. Refer to the Brake Master Cylinder Component Test in this procedure.

Was a concern found?
Yes
INSTALL a new brake master cylinder.
REFER to: Brake Master Cylinder - RHD (206-06, Removal and Installation) /
Brake Master Cylinder - LHD (206-06, Removal and Installation).
TEST the system for normal operation.
No
VERIFY the customer concern.

PINPOINT TEST B : PEDAL EASES DOWN SLOWLY
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
B1: CHECK THE BRAKE PEDAL OPERATION
1
Depress the brake pedal.

Does the pedal ease slowly?
Yes
GO to B2.
No
Refer to the Brake Master Cylinder Component Test in this procedure.
B2: CHECK FOR BRAKE SYSTEM LEAKS
1
Check for external brake system leaks.

Are any leaks present?
Yes
REPAIR as necessary. ADD fluid and BLEED the brake system.
REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).
TEST the system for normal operation.
No
GO to B3.
B3: CHECK THE AIR INTAKE FILTER
1
Check the air intake filter.

Is the filter damaged in any way
Yes
REPAIR as necessary. TEST the system for normal operation.
No
GO to B4.
B4: PERFORM A BRAKE MASTER CYLINDER BYPASS CONDITION TEST
1
Carry out a brake master cylinder bypass Condition Test. Refer to the Brake Master Cylinder Component Test in this procedure.

Was a concern found?
Yes
INSTALL a new brake master cylinder.
REFER to: Brake Master Cylinder - RHD (206-06, Removal and Installation) /
Brake Master Cylinder - LHD (206-06, Removal and Installation).
TEST the system for normal operation.
No
GO to B5.
B5: CHECK THE BRAKE BOOSTER CHECK VALVE
1
Disconnect the brake booster check valve vacuum hose at the manifold.
2
Blow into the hose attached to the brake booster check valve.

Does air pass through the valve?
Yes
INSTALL a new brake booster check valve.
No
GO to B6.
B6: CHECK THE BRAKE BOOSTER CHECK VALVE VACUUM
1
Run the engine at idle.
2
Using a suitable vacuum gauge, check the vacuum pressure.

Is the vacuum pressure above 40.5 kPa (0.4 bar) with the brake booster non-operational?
Yes
VERIFY the customer concern.
No
INSTALL a new brake booster check valve vacuum hose. TEST the system for normal operation.
B7: CHECK THE MASTER CYLINDER
1
Carry out a master cylinder condition test. Refer to the Brake Master Cylinder Component Test in this procedure.

was a concern found?
Yes
INSTALL a new brake master cylinder.
REFER to: Brake Master Cylinder - RHD (206-06, Removal and Installation) /
Brake Master Cylinder - LHD (206-06, Removal and Installation).
TEST the system for normal operation.
No
GO to B2.

PINPOINT TEST C : BRAKE LOCK UP DURING LIGHT BRAKE PEDAL FORCE
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
C1: CHECK THE BRAKE BOOSTER
1
Check the brake booster push rod alignment and pedal travel.

Is the push rod and pedal travel OK?
Yes
TEST the brake pedal application. GO to Pinpoint Test D.
No
INSTALL a new brake booster.
REFER to: Brake Booster - LHD (206-07, Removal and Installation) /
Brake Booster - RHD (206-07, Removal and Installation).
TEST the system for normal operation.

PINPOINT TEST D : EXCESSIVE BRAKE PEDAL EFFORT
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
D1: CHECK BRAKE APPLICATION
1
With the engine off, apply and release the brake pedal five times to deplete all vacuum from the brake booster. Apply the brake pedal, hold with light pressure. Start the engine.

Does the brake pedal hold?
Yes
GO to D2.
No
GO to D3.
D2: CHECK THE BRAKE BOOSTER FOR LEAKS
1
Run the engine at approximately 1000rpm, release the accelerator pedal and turn the engine off. Wait 90 seconds and apply the brakes. Two or more brake applications should be power assisted.

Does the brake booster work?
Yes
VERIFY the customer concern.
No
GO to D4.
D3: CHECK THE BRAKE PEDAL LINKAGE
1
Disconnect the actuator rod from the pedal pin and fully depress the brake pedal.

Did the pedal move freely?
Yes
VERIFY the customer concern.
No
INSTALL new brake pedal and bracket.
REFER to: Brake Pedal and Bracket (206-06, Removal and Installation).
TEST the system for normal operation.
D4: CHECK THE BRAKE BOOSTER CHECK VALVE
1
Disconnect the brake booster check valve vacuum hose at the manifold.
2
Blow into the hose attached to the brake booster check valve.

Does air pass through the valve?
Yes
INSTALL a new brake booster check valve. TEST the system for normal operation.
No
GO to D5.
D5: CHECK THE BRAKE BOOSTER CHECK VALVE VACUUM
1
Run the engine at idle.
2
Using a suitable vacuum gauge, check the vacuum pressure.

Is the vacuum pressure above 40.5 kPa (0.4 bar) with the brake booster non-operational?
Yes
GO to D6.
No
INSTALL a new vacuum hose and fittings. TEST the system for normal operation.
D6: CHECK THE BRAKE BOOSTER
1
Check the brake booster. REFER to the Brake Booster Operation Check in this procedure.

Is the brake booster OK?
Yes
VERIFY the customer concern.
No
INSTALL a new brake booster.
REFER to: Brake Booster - LHD (206-07, Removal and Installation) /
Brake Booster - RHD (206-07, Removal and Installation).
TEST the system for normal operation.

PINPOINT TEST E : BRAKE NOISE
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
E1: CHECK VACUUM
1
Disconnect the brake vacuum hose from the brake booster.
2
Connect a vacuum/pressure tester to the vacuum hose.
3
Ignition switch in position III.
4
Run the engine at normal operating temperature.
5
Record the vacuum reading.

Is the vacuum reading 40.5kPa (12in - Hg)?
Yes
GO to E2.
No
LOCATE and REPAIR the source of low vacuum. TEST the system for normal operation.
E2: INSPECT SYSTEM
1
Ignition switch in position 0.
2
Reconnect the vacuum hose.
3
Inspect the brake booster, rubber grommet, and all vacuum plumbing for cracks, holes, bad connections, or missing clamps.
4
Pump the brake pedal five times to exhaust the vacuum. Push down on the brake pedal and hold.

Does the brake pedal move down when the engine is started?
Yes
Vacuum system is OK.
No
GO to E3.
E3: CHECK POWER BRAKE BOOSTER CHECK VALVE
1
Check the brake booster check valve.

Is the power brake booster check valve OK?
Yes
CHECK the brake booster. Refer to Brake Booster Component Test in this procedure. INSTALL a new brake booster as necessary. TEST the system for normal operation.
No
INSTALL a new brake booster check valve. TEST the system for normal operation.

PINPOINT TEST F : SLOW OR INCOMPLETE BRAKE PEDAL RETURN
TEST CONDITIONS DETAILS/RESULTS/ACTIONS
F1: CHECK FOR BRAKE PEDAL RETURN
1
Run the engine at approximately 1200rpm whilst making several brake applications.
2
Pull the brake pedal upwards with approximately 44.5 N (10 lbs) force.
3
Release the brake pedal and measure the distance to the floor panel and note the reading.
4
Make a hard brake application.
5
Release the brake pedal and measure the distance to the floor panel and note the reading.
6
Compare the measurements.

Did the brake pedal return to its original position?
Yes
VERIFY the customer concern.
No
GO to F2.
F2: CHECK FOR BRAKE PEDAL BINDING
1
Check the brake pedal for free operation.

Did the brake pedal operate freely?
Yes
INSTALL a new brake booster.
REFER to: Brake Booster - LHD (206-07, Removal and Installation) /
Brake Booster - RHD (206-07, Removal and Installation).
TEST the system for normal operation.
No
INSTALL new brake pedal and bracket.
REFER to: Brake Pedal and Bracket (206-06, Removal and Installation).
TEST the system for normal operation.

Component Tests

Hydraulic Leak Check

NOTE:
NOTE:There is a common clutch and brake fluid reservoir, therefore it is possible that a clutch leak can lead to reduction in the reservoir level.

It is possible that all evidence of fluid leakage may have washed off if the vehicle has been operated in rain or snow, as brake fluid is water-soluble. Refill the system, bleed then apply the brakes several times. Examine the system to verify that the reservoir fluid level is actually dropping. Locate and repair the external leak. If the fluid level drops and no external leak can be found, check for a brake master cylinder bore end seal leak.

Brake System Check

Brake Pedal Reserve Check

Where a low brake pedal or the feel of a bottomed-out condition exists, check for brake pedal reserve.

  1. Operate the engine at idle with the transaxle in the NEUTRAL position.
  1. Apply the brake pedal lightly three or four times.
  1. Allow 15 seconds for the vacuum to replenish the brake booster.
NOTE:
NOTE:This increased resistance may feel like something has bottomed out.
  1. Apply the brake pedal until it stops moving downward or an increased resistance to the pedal travel occurs.
  1. Hold the brake pedal in the applied position and raise the engine speed to approximately 2000 rpm.
NOTE:
NOTE:The additional movement of the brake pedal is the result of the increased engine manifold vacuum which exerts more force on the brake booster during engine rundown. This means that additional stroke is available in the brake master cylinder and the brake system is not bottoming out.
  1. Release the accelerator pedal and observe that the brake pedal moves downward as the engine returns to idle speed.

Brake Booster Functional Test

Inspect all hoses and connections. All unused vacuum connectors should be capped. Hoses and their connections should be correctly secured and in good condition with no holes and no collapsed areas. Inspect the check valve on the brake booster for damage.

Brake Booster Operation Check

  1. Check the hydraulic brake system for leaks or low fluid.
  1. With the transaxle in the NEUTRAL position, stop the engine and apply the parking brake. Apply the brake pedal several times to exhaust all the vacuum in the system.
  1. With the engine turned off and the vacuum in the system exhausted, apply the brake pedal and hold it down. Start the engine. If the vacuum system is operating, the brake pedal will tend to move downward under constant foot pressure. If no motion is felt, the vacuum booster system is not functioning.
  1. Remove the vacuum hose from the brake booster. Manifold vacuum should be available at the brake booster end of the hose with the engine at idle speed and the transaxle in the NEUTRAL position. Make sure that all unused vacuum outlets are correctly capped, hose connectors are correctly secured and vacuum hoses are in good condition. When it is established that manifold vacuum is available to the brake booster, connect the vacuum hose to the brake booster and repeat Step 3. If no downward movement of the brake pedal is felt, install a new brake booster.
    REFER to: Brake Booster - LHD (206-07, Removal and Installation) /
    Brake Booster - RHD (206-07, Removal and Installation).
  1. Operate the engine a minimum of 10 seconds at fast idle. Stop the engine and let the vehicle stand for 10 minutes. Then, apply the brake pedal with approximately 89 N (20 lb) force. The pedal feel (brake application) should be the same as that noted with the engine operating. If the brake pedal feels hard (no power assist), install a new vacuum check valve and then repeat the test. If the brake pedal still feels hard, install a new brake booster.
    REFER to: Brake Booster - LHD (206-07, Removal and Installation) /
    Brake Booster - RHD (206-07, Removal and Installation).
    If the brake pedal movement feels spongy, bleed the brake system.
    REFER to: Brake System Bleeding (206-00 Brake System - General Information, General Procedures) /
    Brake System Pressure Bleeding (206-00 Brake System - General Information, General Procedures).

Brake Master Cylinder

Usually, the first and strongest indicator of anything wrong with the braking 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 the brake warning indicator illumination and the fluid level in the master cylinder reservoir.

Normal Conditions

The following conditions are considered normal and are not indications that the brake master cylinder is in need of service.

  • Modern 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 of another vehicle, of the same model and year.
  • During normal operation of the brake pedal, the fluid level in the reservoir will rise during brake pedal application and fall during release. The net fluid level (i.e., after brake pedal application and release) will remain unchanged.
  • A trace of brake fluid will 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.
  • The fluid level will fall with brake shoe and lining wear.

Abnormal Conditions

NOTE:
NOTE:Prior to performing 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 with the braking system. The diagnostic procedure and techniques use brake pedal feel, warning indicator illumination and low brake fluid level as indicators in diagnosing braking system concerns. The following conditions are considered abnormal and indicate that the brake master cylinder is in need of service.

  • The brake pedal goes down fast. This could be caused by an external or internal leak.
  • The brake pedal eases down slowly. This could be caused by an external or internal leak.
  • The brake pedal is low and 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.
  • The brake pedal effort is excessive. This may be caused by a bind or obstruction in the pedal or linkage, clogged fluid control valve or insufficient booster vacuum.
  • The rear brakes lock up during light pedal force. This may be caused by incorrect tire pressures, grease or fluid on the brake shoes and linings, damaged brake shoes and linings, incorrectly adjusted parking brake, or damaged or contaminated brake pressure control valves.
  • The brake pedal effort is erratic. This condition could be caused by a brake booster malfunction, extreme caliper piston knock back or incorrectly installed brake shoes and linings.
  • The brake warning indicator is ON. This may be caused by low fluid level, ignition wire routing too close to the fluid level indicator assembly, or float assembly damage.

Bypass Condition Test

  1. Check the fluid in the brake master cylinder reservoir. Fill the brake master cylinder reservoir if low or empty.
  1. Observe the fluid level in the brake master cylinder reservoir. If after several brake applications, the fluid level remains the same, measure the wheel turning torque required to rotate the wheels with the brakes applied as follows:

Place the transaxle in the NEUTRAL position. Raise and support the vehicle.
REFER to: Jacking (100-02, Description and Operation) /
Lifting (100-02, Description and Operation).

Apply the brakes with a minimum of 445 N (100 lb) and hold for approximately 15 seconds. With the brakes still applied, exert a torque on the front wheels of 10.1 Nm (75 lb ft). If either wheel rotates, install a new brake master cylinder.
REFER to: Brake Master Cylinder - LHD (206-06, Removal and Installation) /
Brake Master Cylinder - RHD (206-06, Removal and Installation).

Non-Pressure Leaks

Any empty brake master cylinder reservoir condition may be caused by two types of non-pressure external leaks.

Type 1: An external leak may occur at the brake master cylinder reservoir cap because of incorrect positioning of the gasket and cap. Reposition the cap and gasket.

Type 2: An external leak may occur at the brake master cylinder reservoir mounting seals. Service such a leak by installing new seals.

General Procedures > < Brake System