Jeep Engines - Oljeep

4.7L POWER TECH V-8 353Figure 6 - 13Coolant1. Routine CheckNote: DO NOT remove the radiator cap for routinecoolant level inspections. The coolant level can bechecked at the coolant reserve/overflow tank.The coolant reserve/overflow system provides a quickvisual method for determining coolant level withoutremoving radiator pressure cap. With engine idling andat normal operating temperature, observe coolant levelin reservehverflow tank. The coolant level should bebetween ADD and FULL marks.2. Adding AdditionalDO NOT remove the radiator cap to add coolant tosystem. When adding coolant to maintain correct level,do so at coolant reserve/overflow tank. Removeradiator cap only for testing or when refilling systemafter service. Removing cap unnecessarily can causeloss of coolant and allow air to enter system, whichproduces corrosion. Refer to the owner’s manual forrecommended coolant type to use.Radiator Pressure CapAll radiators are equipped with a pressure cap. This capreleases pressure at some point within a range of 124-145kPa (18-21 psi). The pressure relief point (in pounds) isengraved on top of the cap.The cooling system will operate at pressures slightly aboveatmospheric pressure. This results in a higher coolantboiling point allowing increased radiator cooling capacity.The cap contains a spring-loaded pressure relief valve. Thisvalve opens when system pressure reaches the release rangeof 124- 145 kPa (1 8-21 psi).A vent valve in the center of the cap allows a small coolantflow through the cap when coolant is below boilingtemperature. The valve is completely close when boilingpoint is reached. As the coolant cools, it contracts and createsa vacuum in cooling system This causes the vacuum valve toopen and coolant in reserve/overflow ..Ink to be drawnthrough connecting hose into radiator. If the vacuum valve isstuck shut, radiator hoses will collapse on cool-down.A rubber gasket seals the radiator filler neck. This is doneto maintain vacuum during coolant cool-down and toprevent leakage when system is under pressure.Water Pump(Refer to Figure 6-14.)A centrifugal water pump circulates coolant through thewater jackets, passages, intake manifold radiator core,cooling system hoses and heater core. The pump is drivenfrom the engine crankshaft by a single serpentine drive belt.The water pump impeller is pressed onto the rear of a shaftthat rotates in bearings pressed into the housing. Thehousing has two small holes to allow seepage to escape.The water pump seals are lubricated by the antifreeze in thecoolant mixture. No additional lubrication is necessary.A quick test to determine if the pump is working is to checkif the heater warms properly. A defective water pump willnot be able to circulate heated coolant through the longheater hose to the heater core.Both heater hoses are connected to fittings on the timingchain front cover. The water pump is also mounted directlyto the timing chain cover and is equipped with a nonserviceable integral pulley.Replace water pump assembly if it has any of thefollowing conditions:The body is cracked or damagedWater leaks from shaft seal (evident by traces ofcoolant below vent hole)Loose or rough turning bearing (also inspect viscousfan drive)Impeller rubs either the pump body or timing chaincasekover