Noise and Emission Control Preventive Maintenance
– 222 – Y53-6008
Medium Duty (R10/06)
Piping
• Check exhaust piping for rust, corrosion, or damage.
Replace deteriorated piping before holes appear. If pip-
ing is perforated at any point, temporary patching or lag-
ging is acceptable until you can have permanent repairs
made. On turbocharged engines, check joints at flanges
and mounting brackets for tightness.
Mufflers
NOTE: Use only an exact replacement muffler in
exhaust systems. Certain mufflers contain integral
catalytic converters essential for compliance with
EPA emission standards. Using a noncompliant muf-
fler as a replacement could violate these standards
and also void the emission system’s warranty.
• Check muffler, clamps, and mounting brackets. Tighten if
necessary. Inspect muffler for signs of rust or corrosion.
• Check internal baffling. You can do this by listening for
rattling sounds while tapping the muffler with a rubber
mallet or revving the engine up and down through its nor-
mal operating range.
Exhaust Tail Pipe
• Check the mounting. Tighten as necessary. The miter
cut at the tip of the pipe must be facing the rear of the
vehicle. Do not modify the end of the pipe in any way.
Engine Fan and Shroud
WARNING! Do not work on the fan with the
engine running. The engine fan can engage at
any time without warning. Anyone near the fan
when it turns on could be seriously injured.
Before turning on the ignition, be sure that no
one is near the fan.
• Check all fasteners for tightness. Check for stress cracks
in the shroud. Make sure the shroud is adjusted so that it
does not touch the fan blades.
• Check to verify that the fan is disengaged (not turning)
with the engine running at normal operating tempera-
tures (from cold to the point that the fan engages).
• Check fan blade mounting bolts. Inspect fan blades to be
sure they are not cracked or bent. If problems exist, refer
to the Cooling System section in the Medium Duty
Maintenance Manual for detailed maintenance instruc-
tions.
