Grand Cherokee 2WD V6-3.7L (2008)
Water Pump: Description and Operation
Operation
Operation
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 - 3.7L/4.7L
WATER PUMP BYPASS - 3.7L/4.7L
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
pill partially covers the bypass hole, reducing the amount of bypass flow. This design allows the coolant to reach operating temperature quickly when
cold, while adding extra cooling during normal temperature operation.
Diagnosis and Testing - Water Pump
DIAGNOSIS AND TESTING - WATER PUMP
LOOSE IMPELLER - 3.7L/4.7L/5.7L ENGINES
NOTE: Due to the design of the 3.7/4.7L/5.7L engine water pumps, testing the pump for a loose impeller must be done by verifying coolant flow
in the radiator. To accomplish this refer to the following procedure.
DO NOT WASTE reusable coolant. If solution is clean, drain coolant into a clean container for reuse.
1. Drain coolant until the first row of cores is visible in the radiator See: Cooling System/Service and Repair 4.7L Engine.
2. Leaving the radiator cap off, start the engine. Run engine until thermostat opens.
3. While looking into the radiator through the radiator fill neck, raise engine rpm to 2000 RPM. Observe the flow of coolant from the first row of
cores.
4. If there is no flow or very little flow visable, replace the water pump.
INSPECTING FOR INLET RESTRICTIONS
Inadequate heater performance may be caused by a metal casting restriction in the heater hose inlet.
DO NOT WASTE reusable coolant. If solution is clean, drain the coolant into a clean container for reuse.
WARNING: Do not loosen the radiator draincock with the system hot and under pressure. Serious burns from the coolant can occur.
1. Drain sufficient coolant from the radiator to decrease the level below the heater hose inlet. On 4.7L engines this requires complete draining.
2. Remove the heater hose.
3. Inspect the inlet for metal casting flash or other restrictions.