Group 25 Intake and Exhaust System Design and Function
Design and Function
Intake and Exhaust System
Preheater
Selected versions of the D12 are equipped with a pre-
heater. Its purpose is to warm air in the intake manifold
when starting the engine. This heated air eases starting
at very low temperatures and reduces engine smoking
when starting a cold engine. The following conditions are
required to engage the preheater:
•
The parking brake must be applied.
•
The power take-off must not be engaged.
The preheater does not engage at coolant temperatures
over 10
C (50
F). At a coolant temperature of 10
C
(50
F), the preheating time is 25 seconds. At coolant
temperatures below –15
C(5
F), the preheating time is
55 seconds. Preheating time increases linearly between
10
C (50
F) and –15
C(5
F).
The post-heating time is always the same as the pre-
heating time.
T2006975
Fig. 1: Preheater
D12C
The D12C is equipped with a new preheater. The func-
tion of the starting heater is similar for both vehicle
variants, but the location of the relay differs. The pre-
heater on both engine variants is grounded to the engine
block through the intake manifold.
W2003281
Fig. 2: Preheater, D12C
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