antifreeze in the coolant mixture. Additional lubrica-
tion is not necessary.
OPERATION
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core,
this coolant absorbs the heat generated when the
engine is running. The pump is driven by the engine
crankshaft via a drive belt.
WATER PUMP BYPASS—4.7L
DESCRIPTION
The 4.7L engine uses an internal water/coolant
bypass system. The design uses galleries in the tim-
ing chain cover to circulate coolant during engine
warm-up preventing the coolant from flowing
through the radiator. The thermostat uses a stub
shaft located at the rear of the thermostat (Fig. 9) to
control flow through the bypass gallery.
OPERATION
When the thermostat is in the closed position the
bypass gallery is not obstructed allowing 100% flow.
When the thermostat is in the open position the stub
shaft enters the bypass gallery obstructing bypass
coolant flow by 50%. This design allows the coolant
to reach operating temperature quickly when cold,
while adding extra cooling during normal tempera-
ture operation.
Fig. 7 Radiator—Typical
1 – RADIATOR
2 – A/C CONDENSER (IF EQUIPPED)
3 – TRANSMISSION AUXILIARY OIL COOLER
Fig. 8 Water Pump Location—Typical
1 – WATER PUMP BYPASS HOSE
2 – FAN BLADE ASSEMBLY
3 – VISCOUS FAN DRIVE
4 – WATER PUMP AND PULLEY
Fig. 9 Water/Coolant Bypass Flow and Thermostat—
4.7L Engine
1 – FROM HEATER
2 – FROM RADIATOR
3 – TO WATER PUMP
4 – ENGINE BYPASS
5 – THERMOSTAT
7 - 6 COOLING SYSTEM DN
DESCRIPTION AND OPERATION (Continued)
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