Dodge ram truck 3500 1996 Service Manual page 197

B R BRAKES 5 • 13
DIAGNOSIS AND TESTING (Continued)
Maximum allowable rotor runout is 0.127 mm
(0.005 in.).
DIAL
INDICATOR
J 8 9 0 5 - 6 8
Fig. 12 Checking Rotor Runout And Thickness
Variation
MOTOR THICKNESS VARIATION
Variations in rotor thickness will cause pedal pul­
sation, noise and shudder.
Measure rotor thickness at 6-to-12 points around
the rotor face (Fig. 13).
Position the micrometer approximately 25.4 mm ( 1
in.) from the rotor outer circumference for each mea­
surement.
Thickness should not vary by more than 0.025 mm
(0.001 in.) from point-to-point on the rotor. Machine
or replace the rotor If necessary.
MICROMETER
ROTOR
TAKE MINIMUM
OF 6 MEASUREMENTS
AROUND ROTOR
J9405-103
Fig. 13 Measuring Rotor Thickness
BRAKE DRUi
The maximum allowable diameter of the drum
braking surface is stamped or cast into the drum
outer edge. Generally, a drum can be machined to a
maximum of 1.52 mm (0.060 in.) oversize. Always
replace the drum i f machining would cause drum
diameter to exceed the size limit indicated on the
drum.
BRAKE DRUM RUNOUT
Measure drum diameter and runout with an accu­
rate gauge. The most accurate method of measure­
ment involves mounting the drum in a brake lathe
and checking variation and runout with a dial Indi­
cator.
Variations in drum diameter should not exceed
0.076 mm (0.003 in.). Drum runout should not exceed
0.20 mm (0.008 in.) out of round. Machine the drum
if runout or variation exceed these values. Replace
the drum i f machining causes the drum to exceed the
maximum allowable diameter.
BRAKE LINE AND HOSES
Flexible rubber hose is used at both front brakes
and at the rear axle junction block. Inspect the hoses
whenever the brake system is serviced, at every
engine oil change, or whenever the vehicle is in for
service.
Inspect the hoses for surface cracking, scuffing, or
worn spots. Replace any brake hose immediately i f
the fabric casing of the hose is exposed due to cracks
or abrasions.
Also check brake hose'installation. Faulty installa­
tion can result in kinked, twisted hoses, or contact
with the wheels and tires or other chassis compo­
nents. A l l of these condition can lead to scuffing,
cracking and eventual failure.
The steel brake lines should' be inspected periodi­
cally for evidence of corrosion, twists, kinks, leaks, or
other damage. Heavily corroded lines will eventually
rust through causing leaks. I n any case, corroded or
damaged brake lines should be replaced.
Factory replacement brake lines and hoses are rec­
ommended to ensure quality, correct length and supe­
rior fatigue life. Care should be taken to make sure
that brake line and hose mating surfaces are clean
and free from nicks and burrs. Also remember that
right and left brake hoses are not interchangeable.
Use new copper seal washers at all caliper connec­
tions. Be sure brake line connections are properly
made (not cross threaded) and tightened to recom­
mended torque.
BRAKE FLUID
CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts Indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid i n clear glass jar. I f fluid sepa-