freightliner Custom Classic MT45 2022 Maintenance Manual page 127

Exhaust
6. Check all sensors attached to the ATD for leaks
or damaged wires. No leaks are allowed.
7. Check the DPF exterior surface for dents or
other damage. A dent over 3 inches (76 mm) in
diameter and 1/4-inch (6-mm) deep could cause
internal damage to the DPF, causing it to mal-
function.
8. Check the SCR catalyst for dents and other
damage.
9. Check for heat discoloration on the surface of
the ATD. Heat discoloration may indicate internal
damage; especially around the DPF.
NOTE: Diesel exhaust fluid creeps, causing
white crystals to form around the line fittings.
The presence of crystals does not mean the
system has a leak. Replacing fittings or trouble-
shooting components is not necessary unless
there is a system failure or a fault code.
10. Check the DEF tank, pump, metering unit, and
lines for leaks. See
Chassis Workshop Manual for repair procedures.
11. Check any wires, lines, or hoses within 4 inches
(10 cm) of the exhaust system for heat damage.
Repair or reroute as needed.
Diesel Exhaust Fluid (DEF) Filter
Replacement
The Environmental Protection Agency's 2010 regula-
tions require lower nitrogen oxide (NOx) exhaust
emissions. Selective catalytic reduction (SCR) uses
diesel exhaust fluid (DEF) to lower NOx emissions in
the vehicle exhaust. A filter in the DEF pump pre-
vents clogging of the DEF metering unit injection
nozzle.
See the engine manufacturer's maintenance manual
for DEF filter replacement instructions and mainte-
nance intervals.
EPA07 Exhaust System
Inspecting
Definitions of ATS Components
Refer to the following list of definitions of ATS com-
ponents.
Walk-In Van Chassis Maintenance Manual, November 2015
Group 49 of the Walk-In Van
• Aftertreatment System (ATS)—the entire ex-
haust system from the turbocharger to the ex-
haust stack or tail pipe.
• Aftertreatment Device (ATD)—a muffler-like can-
ister that houses a DPF and sensors.
• Diesel Particulate Filter (DPF)—a filter that col-
lects and holds particulate matter (soot and
ash).
• Diesel Oxidation Catalyst (DOC)—oxidizes hy-
drocarbons and reduces NOx.
• Sensors—detect temperatures and pressure
within the ATS.
• Diffuser—a device, used as a deflector, for dis-
tributing, mixing, and reducing the velocity of air
flow.
IMPORTANT: The Environmental Protection
Agency's 2007 regulations require lower ex-
haust emissions, thus requiring new exhaust
system components. See
the aftertreatment device (ATD), which is part of
the aftertreatment system (ATS), requires spe-
cial attention during regularly scheduled mainte-
nance inspections. If any discrepancies are dis-
covered, refer to the engine manufacturer's
service literature for repair instructions.
Inspection
1. Check for leakage at the clamp that attaches the
exhaust pipe to the turbocharger exhaust outlet.
If leakage exists, tighten the nut on the clamp to
the required torque. If leakage persists, install a
new clamp.
2. Check the exhaust pipe, bellows, and each ex-
haust seal clamp for leakage, wear, cracks, or
damage. Replace damaged components as
needed. If leakage exists at a clamp, tighten the
nuts to the required torque. If leakage persists,
install a new exhaust seal clamp. Do not reuse
seal clamps. Once a seal clamp is loosened or
removed, it must be replaced.
3. If present, check the condition of the insulation
material around the exhaust pipe between the
turbocharger and the ATD.
4. Check the ATD mounting bands for tightness.
Tighten to 30 lbf·ft (41 N·m) if needed. Do not
overtighten.
49
Fig. 2. In particular
49/3