TM 5-3825-226-24COOLING SYSTEMThe cooling system is a pressure type. Theengine has the temperature regulator at the outlet. Thecooling system is equipped with a shunt line.A pressure type cooling system gives twoadvantages. The first advantage is that the coolingsystem can have safe operation at a temperature that ishigher than the normal boiling (steam) point of water.The second advantage is that this type system preventscavitation (the sudden making of low pressure bubblesin liquids by mechanical forces) in the water pump.With this type system, it is more difficult for air or steampockets to be made in the cooling system.The cause for an engine getting too hot isgenerally because regular inspections of the coolingsystem were not made. Make a visual inspection of thecooling system before testing with testing equipment.VISUAL INSPECTION OF THE COOLING SYSTEM1.Check coolant level in the cooling system.2.Look for leaks in the system.3.Look for bent radiator fins. Be sure that air flowthrough the radiator does not have a restriction.4.Inspect the drive belt for the fan.5.Check for damage to the fan blades.6.Look for air or combustion gas in the coolingsystem.7.Inspect the pressure cap and the sealing surfacefor the cap. The sealing surface must be clean.TESTING THE COOLING SYSTEMRemember that temperature and pressure worktogether. When making a diagnosis of a cooling systemproblem, temperature and pressure must both bechecked. Cooling system pressure will have an effecton cooling system temperatures. For an example, lookat the chart to see the effect of pressure and heightabove sea level on the boiling (steam) point of water.Test Tools for Cooling SystemTools Needed:9S9102 Thermistor Thermometer Group.9S7373 Air Meter Group.1P5500 Portable Photolach Group.9S8140 Cooling System Pressurizing Pump Group.The 9S9102 Thermistor Thermometer Group isused in the diagnosis of overheating (engine running toohot) or overcooling (engine runs too cool) problems.This group can be used to check temperatures inseveral different parts of the cooling system.9S9102 THERMISTOR THERMOMETER GROUPThe 1P5500 Portable Phototach Group is usedto check the fan speed.1P5500 PORTABLE PHOTOTACH GROUP2-69
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