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 slo
w
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.
