COOLING SYSTEM - V8 (Operation): DESCRIPTION AND OPERATION

COOLING SYSTEM - V8

26-2-10 DESCRIPTION AND OPERATION

Operation

Coolant flow - Engine warm up
Refer to illustration.
 

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 COOLING SYSTEM - V8, DESCRIPTION AND OPERATION, Cooling system coolant flow.

During warm-up the coolant pump moves fluid through the cylinder block and it emerges from the inlet manifold outlet 
pipe. From the outlet pipe, the warm coolant flow is prevented from flowing through the radiator because the 
thermostat is closed. The coolant is directed into the heater circuit.

Some coolant from the by-pass pipe can pass through small sensing holes in the flow valve. The warm coolant enters 
a tube in the thermostat housing and surrounds 90% of the thermostat sensitive area. Cold coolant returning from the 
radiator bottom hose conducts through 10% of the thermostat sensitive area. In cold ambient temperatures the engine 
temperature can be raised by up to 10

°

C (50

°

F) to compensate for the heat loss of the 10% exposure to the cold 

coolant returning from the radiator bottom hose.

At engine idle speed, the by-pass valve is closed only allowing the small flow through the sensing holes. As the engine 
speed increases above idle, the greater flow and pressure from the pump overcomes the light spring and opens the 
by-pass flow valve. The flow valve opens to meet the engines cooling needs at higher engine speeds and prevents 
excess pressure in the system. With the thermostat closed, maximum flow is directed through the heater circuit.

The heater matrix acts as a heat exchanger reducing coolant temperature as it passes through the matrix. Coolant 
emerges from the matrix and flows into the coolant pump feed pipe and recirculated around the heater circuit. In this 
condition the cooling system is operating at maximum heater performance.

Coolant flow - Engine hot
As the coolant temperature increases the thermostat opens. This allows some coolant from the outlet housing to flow 
through the top hose and into the radiator to be cooled. The hot coolant flows from the left tank in the radiator, along 
the tubes to the right tank. The air flowing through the fins between the tubes cools the coolant as it passes through 
the radiator.

A controlled flow of the lower temperature coolant is drawn by the pump and blended with hot coolant from the by-
pass and the heater return pipes in the pump feed pipe. The pump then passes this coolant into the cylinder block to 
cool the cylinders.