Century Estate Wagon L4-151 2.5L (1985)
Brake Rotor/Disc: Technical Service Bulletins
Correction
CORRECTION
Test Drive
Before any diagnosis is performed, it is essential that the vehicle be road tested to determine the exact nature of the problem and to get a feel for the
vehicle vibration characteristics. The road test is used to determine whether brake pulsation is present or whether the vibration is due to some other cause
(tire and wheel vibration/balance, bent or out-of-round wheel rims, drivetrain, etc.).
When a brake pulsation condition is confirmed, a road test will determine whether the front or rear brakes are the cause.
If vibration/roughness is determined to be from a source other than brakes, perform necessary repairs.
Brakes should be tested while driving on a dry, clean and reasonably smooth road surface. Rear brake pulsation is more easily isolated. When rear brake
pulsation has been eliminated or repaired, a full brake system test can be used to diagnose front brake pulsation. Begin by testing the rear brakes as
follows:
Rear Brake Pulsation Test
1.
Accelerate to approximately 20 mph.
2.
Place gear selector in neutral.
3.
While holding the parking brake release in the return position, lightly apply the parking brake to stop the vehicle. (Failure to hold the parking
brake release in the return position could result in rear brake "lock").
4.
OBSERVE: Does the parking brake pedal pulsate? Is there noticeable vibration in the vehicle (different than road induced)?
5.
If either of these conditions is present, refinish or replace drums/rotors as required.
If no rear brake pulsation is indicated, test the front brakes as follows:
Front Brake Pulsation Test (Full Brake System)
1.
Perform 20 to Zero mph brake test:
a.
Accelerate vehicle to 20 mph.
b.
Place selector in neutral.
c.
Apply brakes lightly to stop the vehicle. If pulsation is felt, service front brakes as described in this bulletin. If no pulsation is present,
continue to Step 2.
2.
Perform 45 to 50 mph brake test:
a.
Accelerate vehicle to 50 mph.
b.
Place selector in neutral.
c.
Apply brakes using medium pedal pressure. If pulsation is felt, service front brakes as described in this bulletin. If no pulsation is present,
continue to Step 3.
3.
Heat up the brake system by performing 10 stops from approximately 30 mph using medium pedal pressure. Then repeat 20 to Zero mph test in
Step 1.
a.
If pulsation is felt, service front brakes as described in this bulletin.
b.
If no pulsation is present, check tires and drivetrain components for other possible causes of customer complaint.
ROTOR REFINISHING
Rotor refinishing should only be performed when rotor thickness variation (non-parallelism) is present or when the rotor surface has scoring grooves
deeper than .015 inches. Replacement rotors, taken from stock, should be mounted and checked for lateral run-out, and if run-out exists, then the rotor
must be refinished on the vehicle.
When rotors are refinished, a correct surface finish is important for satisfactory braking. Following a light finish-cutting operation of between .001 and
.002 inches, correct surface should be obtained by rubbing with 120 grit emery cloth. Surface finish may be checked by running a fingernail over the
surface of a new rotor front stock or one from a known good vehicle. For best results, cutting equipment should be maintained in correct working
