Dodge Durango

 Service Manual

Cooling System » Description and operation
Water pump bypass-4.7L

DESCRIPTION

The 4.7L engine uses an internal water/coolant bypass system. The design uses galleries in the timing 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.

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

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 temperature operation.

Cooling system

Coolant reserve/overflow system

Thermostat-5.2L/5.9L engines

Thermostat-4.7L engine

Radiator pressure cap

Radiator

Water pump

Water pump bypass-4.7L

Water pump bypass hose-5.2L/5.9L engines

Automatic transmission oil coolers

Automatic belt tensioner

Block heater

Hose clamps

Viscous fan drive