Envoy 2WD V8-5.3L VIN P (2004)
Coolant: Description and Operation
Cooling System
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling
system is designed to remove approximately 1/3 of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the coolant does
not flow to the radiator until the thermostat opens. This allows the engine to warm quickly.
Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Coolant will then be pumped through the water pump outlet
and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders, where the coolant absorbs heat.
Some coolant is also pumped from the water pump to the heater core, then back to the water pump. This provides the passenger compartment with heat
and defrost.
The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the
water jackets surrounding the combustion chambers and valve seats, where the coolant absorbs additional heat.
Coolant is also directed to the throttle body. There the coolant circulates through passages in the casting. During initial start up, the coolant assists in
warming the throttle body. During normal operating temperatures, the coolant assists in keeping the throttle body cool.
From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is
warmed, or the coolant will flow through the thermostat and into the radiator where the coolant is cooled and the coolant cycle is completed.
Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components,
which are described below:
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The coolant
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The radiator
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The pressure cap
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The coolant recovery system
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The air baffles and seals
Coolant
The engine coolant is a solution made up of a 50-50 mixture of DEX-COOL and suitable drinking water. The coolant solution carries excess heat away
from the engine to the radiator, where the heat is dissipated to the atmosphere.
