Toyota 1 MZ–FE Manual page 314

EG2–314
The cooling system is composed of the water jacket (inside the cylinder block and cylinder head),
radiator, water pump, thermostat, electronically controlled hydraulic cooling fan, hoses and other
components.
Coolant which is heated in the water jacket is pumped to the radiator, through which a cooling
fan blows air to cool the coolant as it passes through. Coolant which has been cooled is then sent
back to the engine by the water pump, where it cools the engine.
The water jacket is a network of channels in the shell of the cylinder block and cylinder head
through which coolant passes. It is designed to provide adequate cooling of the cylinders and
combustion chambers which become heated during engine operation.
RADIATOR
The radiator, mounted in the front of the vehicle, performs the function of cooling the coolant
which has passed through the water jacket and become hot. The radiator consists of an upper
tank and lower tank, and a core which connects the two tanks. The upper tank contains the inlet
for coolant from the water jacket. The lower tank has an outlet and drain plug for the coolant. The
core contains many tubes through which coolant flows from the upper tank to the lower tank as
well as cooling fins which radiate heat away from the coolant in the tubes.
The air sucked through the radiator by the cooling fan, as well as the wind generated by the
vehicle's travel, passes through the radiator, cooling the coolant. Models with an automatic
transmission include an automatic transmission fluid cooler built into the lower tank of the
radiator. A cooling fan is mounted behind the radiator to assist the flow of air through the
radiator. When the coolant temperature is low, the fan operates slowly to help the engine warm
up, and when the coolant temperature becomes high, the fan speed is increased to provide the air
flow required for cooling.
1MZ–FE ENGINE – COOLING SYSTEM