Manitowoc Published 05-26-17, Control # 238-02 7-17
MLC165-1 SERVICE/MAINTENANCE MANUAL POWER TRAIN
DEF Dosing Module
The DEF dosing module (8, Figure 7-11, page 7-14) injects
a liquid mixture of urea and deionized water (called DEF) into
the exhaust stream ahead of the inlet to the SCR module (6).
Coolant lines run through the dosing module to keep it cool
and operable.
DOC Module
The primary function of the DOC module (9,
Figure 7-11, page 7-14
) is to oxidize the remaining
hydrocarbons in the exhaust to carbon dioxide. It
incorporates a NO
x
sensor, a dP sensor, and two
temperature sensors.
The DOC module does not require maintenance.
DEF Heating and Cooling System
Warm coolant from the engine is routed to the coolant
manifold (3, Figure 7-11, page 7-14
) where it splits into two
paths: one path delivers coolant to the heat exchanger in the
DEF tank (1) to keep the DEF warm, and the other path
delivers coolant to the DEF dosing module (8) to keep it from
overheating.
The coolant solenoid valve (2) adjusts coolant flow according
to the temperature of the DEF in the DEF tank. If the tank
temperature drops below 25° F (–4° C), the ECM will open
the solenoid valve, and engine coolant will flow through the
heat exchanger in the DEF tank.
To keep the DEF flowing during cold temperatures, two
heating elements are provided: one in the DEF supply
module and one in DEF line. The heating elements turn on if
the ambient air temperature sensor reads a temperature
below 25° F (–4° C).
The DEF dosing module (8) will not prime the system until
every component is completely defrosted. If ambient
conditions continue to be cold after the system has primed,
the ECM will command a maintenance heating cycle to
prevent the DEF system from refreezing. This feature will
cycle the heating on and off to the DEF lines, DEF tank, and
dosing module.
NOTE: DEF will freeze at 12° F (–11° C) and when frozen
will expand by 10%. There are no approved
additives to improve the freezing point.
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