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Mitsubishi Galant (2004+). Manual - part 504

BASIC BRAKE SYSTEM DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-3

BASIC BRAKE SYSTEM DIAGNOSIS

INTRODUCTION TO BASIC BRAKE SYSTEM DIAGNOSIS

M1351009700319

Hydraulic brakes are composed of the brake pedal,
master cylinder, brake booster and disc brakes. Mal-
functions such as insufficient braking power or the
generation of noise may occur due to wear, damage
or incorrect adjustment of these components.

BASIC BRAKE SYSTEM DIAGNOSTIC TROUBLESHOOTING STRATEGY

M1351009800316

Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will be sure that you
have exhausted most of the possible ways to find a
basic brake system fault.
1. Gather information from the customer.

2. Verify that the condition described by the

customer exists.

3. Find the malfunction by following the symptom

chart.

4. Verify malfunction is eliminated.

SYMPTOM CHART

M1351009900324

AC305394

BRAKE BOOSTER

MASTER CYLINDER AND
PROPORTIONING VALVES

FRONT DISC BRAKE

REAR DISC BRAKE

<VEHICLE WITHOUT ABS>

SYMPTOM

INSPECTION
PROCEDURE

REFERENCE
PAGE

Vehicle pulls to one side when brakes are applied

P.35A-4

Insufficient braking power

P.35A-4

Increased pedal stroke (Reduced pedal-to-floor board clearance) 3

P.35A-5

Brake drag

P.35A-6

Scraping or grinding noise when brake are applied

P.35A-7

Squealing, groaning or chattering noise when brake are applied

P.35A-8

Squealing noise when brakes are not applied

P.35A-9

Groaning, clicking or rattling noise when brakes are not applied

P.35A-11

BASIC BRAKE SYSTEM DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-4

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: Vehicle Pulls to One Side when Brakes are Applied

DIAGNOSIS

STEP 1. Check for oil, water, etc., on the pad
contact surface of all brakes.

Q: Is oil, water, etc., on the pad contact surface?

YES :

Replace the part and determine the

source/cause of foreign material. Then go to
Step 5.

NO :

Go to Step 2.

STEP 2. Check disc brake pistons for smooth
operation.
(1) With engine not running, depress the brake pedal

rapidly several times to deplete booster vacuum
reserves.

(2) Test each disc brake assembly one at a time.

a. Remove the lower caliper bolt, then remove

caliper from mount.

b. Have an assistant slowly depress the brake

pedal. Confirm piston(s) extend slowly and
smoothly with no jumpiness. Repeat for each
disc brake assembly.

Q: Do (does) the piston(s) move correctly?

YES :

Go to Step 3.

NO :

Disassemble and inspect the brake
assembly (Front: refer to

P.35A-33

, Rear:

refer to

P.35A-36

). Then go to Step 5.

STEP 3. Check brake disc(s) for runout.

Refer to

P.35A-20

Q: Is runout outside of specifications?

YES :

Repair or replace the brake disc(s) as

necessary. Then go to Step 5.

NO :

Go to Step 4.

STEP 4. Check brake discs for correct thickness.

Refer to

P.35A-20

Q: Is the thickness outside of specifications?

YES :

Repair or replace the brake disc(s) as

necessary. Then go to Step 5.

NO :

Perform the brake line bleeding. Then go to
Step 5.

STEP 5. Retest the system.

Q: Is the symptom eliminated?

YES :

The procedure is complete.

NO :

Start over at Step 1. If a new symptom
appears, refer to the appropriate symptom
chart.

INSPECTION PROCEDURE 2: Insufficient Braking Power

DIAGNOSIS

STEP 1. Check that the specified brake fluid is
used, its level is correct, and no contamination is
found.

Q: Is there a fault?

YES :

Refill or replace with the specified brake

fluid DOT 3 or DOT 4. Bleed the brakes if
necessary (Refer to

P.35A-16

). Then go to

Step 7.

NO :

Go to Step 2.

STEP 2. Check for spongy (not firm) brakes.
(1) With engine not running, depress the brake pedal

rapidly several times to deplete the booster
vacuum reserve.

(2) With the brake pedal fully released, depress the

brake pedal slowly until it stops.

(3) With a measuring device (ruler, etc.) next to the

brake pedal, depress the pedal firmly and
measure the distance the pedal traveled.

Q: Is the distance greater than 20 mm (0.8 inch)?

YES :

Bleed the brakes to remove air in the fluid

(Refer to

P.35A-16

). Then go to Step 7.

NO :

Go to Step 3.

BASIC BRAKE SYSTEM DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-5

STEP 3. Check the brake booster function.

Refer to

P.35A-14

Q: Is there a fault?

YES :

Replace the brake booster. Then go to Step

NO :

Go to Step 4.

STEP 4. Check for pinched or restricted brake
tube or hose.

Q: Is there a pinched or restricted brake tube or hose?

YES :

Replace that complete section of brake tube

or brake hose. Then go to Step 7.

NO :

Go to Step 5.

STEP 5. Check for oil, water, etc., on the pad
contact surfaces of all brakes.

Q: Is oil, water, etc., on the pad contact surface?

YES :

Replace the part and determine the

source/cause of foreign material. Recheck
symptom. Then go to Step 7.

NO :

The procedure is complete. If condition
persists for vehicles without ABS, go to Step
6.

STEP 6. Check the proportioning valve operation.
<Vehicles without ABS>

Refer to

P.35A-16

Q: Is there a fault?

YES :

Replace the proportioning valve. Then go to

Step 7.

NO :

Go to Step 7.

STEP 7. Recheck symptom.

Q: Is the symptom eliminated?

YES :

The procedure is complete.

NO :

Start over at step 1. If a new symptom
surfaces, refer to the appropriate symptom
chart.

INSPECTION PROCEDURE 3: Increased Pedal Stroke (Reduced Pedal-to-Floor Board Clearance)

DIAGNOSIS

STEP 1. Check for spongy (not firm) brakes.
(1) With engine not running, depress the brake pedal

rapidly several times to deplete booster vacuum
reserve.

(2) With the brake pedal fully released, depress the

brake pedal slowly until it stops.

(3) With a measuring device (ruler, etc.) next to the

brake pedal, depress the pedal firmly and
measure the distance the pedal traveled.

Q: Is the distance greater than 20 mm (0.8 inch)?

YES :

Bleed the brakes to remove air in the fluid

(Refer to

P.35A-16

). Then go to Step 7.

NO :

Go to Step 2.

STEP 2. Check the pad for wear.

Refer to

P.35A-18

Q: Is the pad thickness outside of specifications?

YES :

Replace the part. Then go to Step 7.

NO :

Go to Step 3.

STEP 3. Check the vacuum hose and check valve
for damage.

Refer to

P.35A-15

Q: Is there a damage?

YES :

Replace the part. Then go to Step 7.

NO :

Go to Step 4.

STEP 4. Check the master cylinder function.

Refer to

P.35A-23

Q: Is there a fault?

YES :

Repair it. Then go to Step 7.

NO :

Go to Step 5.

STEP 5. Check for brake fluid leaks.

Q: Is there a leak?

YES :

Check the connection for looseness,

corrosion, etc. Clean and repair as
necessary. If leaking in any tube or hose
section, replace the complete tube or hose.
Then go to Step 7 .

NO :

Go to Step 6.

BASIC BRAKE SYSTEM DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-6

STEP 6. Check for excessive clearance between
the push rod and primary piston.

Refer to

P.35A-26

Q: Is the clearance outside of specifications?

YES :

Adjust the clearance. Then go to Step 7.

NO :

Go to Step 7.

STEP 7. Recheck symptom.

Q: Is the symptom eliminated?

YES :

The procedure is complete.

NO :

Start over at step 1. If a new symptom
surfaces, refer to the symptom chart.

INSPECTION PROCEDURE 4: Brake Drag

DIAGNOSIS

STEP 1. Check the parking brake operating lever return.

Q: Is the operation faulty?

YES : Repair it. Then go to Step 9.
NO : Go to Step 2.

STEP 2. Check the brake shoe springs for breakage.

Q: Are the brake shoe springs broken?

YES : Replace the spring. Then go to Step 9.
NO : Go to Step 3.

STEP 3. Check the amount of grease at each sliding
section.

Refer to GROUP 36, Parking Brake Lining and Drum

P.36-8

Q: Is the grease amount low?

YES : Apply grease. Then go to Step 9.
NO : Go to Step 4.

STEP 4. Check the parking brake pull amount.

Refer to GROUP 36, On-vehicle Service

− Parking Brake lever

Stroke Check and Adjustment

P.36-4

Q: Is there a fault?

YES : Adjust it. Then go to Step 9.
NO : Go to Step 5.

AC210519 AB

PARKING BRAKE
OPERATING LEVER

AC210519AC

SHOE
SPRINGS

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