15-38
Relay box
A/C
compressorHFM (intake air
temperature)Cooling fan
module
MB 5 A/T (ATF
temperature)Coolant
temperature
sensor
(12) Cooling fan control
A. Overview of cooling fan and A/C compressor
The cooling system maintains the engine temperature at an efficient level during all engine operating
conditions. The water pump draws the coolant from the radiator. The coolant then circulates through
water jackets in the engine block, the intake manifold, and the cylinder head. When the coolant reaches
the operating temperature of the thermostat, the thermostat opens. The coolant then goes back to the
radiator where it cools. The heat from automatic transmission is also cooled down through the radiator
by circulating the oil through the oil pump. ECU controls the electric cooling fans with three cooling fan
relays to improve the engine torque and air conditioning performance.
For detailed information, refer to Chapter "Air Conditioning System".
B. Components
D20DTR ECU
Refrigerant
07-6
1. GENERAL DESCRIPTION
The cooling system maintains the engine temperature at an efficient level during all engine
operating conditions. When the engine is cold, the cooling system cools the engine slowly or not
at all. This slow cooling of the engine allows the engine to warm up quickly. The cooling system
includes a radiator and recovery subsystem, cooling fans, a thermostat and housing, a water
pump, and a water pump drive belt. The timing belt drives the water pump. All components must
function properly for the cooling system to operation. The water pump draws the coolant from the
radiator.
The coolant then circulates through water jackets in the engine block, the intake manifold, and
the cylinder head. When the coolant reaches the operating temperature of the thermostat, the
thermostat opens. The coolant then goes back to the radiator where it cools. This system directs
some coolant through the hoses to the heat core. This provides for heating and defrosting. The
coolant reservoir is connected to the radiator to recover the coolant displaced by expansion from
the high temperatures. The coolant reservoir maintains the correct coolant level. The cooling
system for this vehicle has no radiator cap or filler neck. The coolant is added to the cooling
system through the coolant reservoir.
