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Visual Inspection Of The Cooling System
Cooling systems that are not regularly inspected are the cause for increased engine temperatures. Make a visual inspection of the cooling system before a test is made with test equipment.
Steam or hot coolant can cause severe burns.Do not loosen the filler cap or the pressure cap on a hot engine.Allow the engine to cool before removing the filler cap or the pressure cap.
Check the coolant level in the cooling system.
Look for leaks in the system.
Look for air or combustion gas in the cooling system.Testing The Cooling System
Illustration 1 g00286266
Boiling Point Of WaterRemember that temperature and pressure work together. When a diagnosis is made of a cooling system problem, temperature and pressure must be checked. Cooling system pressure will have an effect on the cooling system temperature. For an example, refer to illustration 1. This will show the effect of pressure on the boiling point (steam) of water. This will also show the effect of height above sea level.Test Tools For Cooling System
Table 1
Tools Needed     Quantity    
4C-6500 Digital Thermometer     1    
Making contact with a running engine can cause burns from hot parts and can cause injury from rotating parts.When working on an engine that is running, avoid contact with hot parts and rotating parts.
Illustration 2 g00286267
4C-6500 Digital Thermometer The 4C-6500 Digital Thermometer is used in the diagnosis of overheating problems or overcooling problems. This group can be used to check temperatures in several different parts of the cooling system. Refer to the testing procedure in Operating Manual, NEHS0554.Test For The Water Temperature Indicator Or Sensor
Table 2
Tools Needed     Quantity    
4C-600     Digital Thermometer     1    
or    
2F-7112     Thermometer     1    
6B-5072     Terminal Bushing     1    
Illustration 3 g00322896
Test Location (Typical Example) (1) Plug.Check the accuracy of the water temperature indicator or water temperature sensor if either of the conditions that follow are found:
A normal temperature is indicated, but the engine is too hot. A loss of coolant is found.
A hot temperature is indicated, but there is no loss of coolant.Remove the plug (1). Install the 4C-6500 Digital Thermometer or the 2F-7112 Thermometer and the 6B-5072 Terminal Bushing. A temperature indicator of known accuracy can also be used to make this check.
Personal injury can result from escaping fluid under pressure.If a pressure indication is shown on the indicator, push the release valve in order to relieve pressure before removing any hose from the radiator.
Start and run the engine until the temperature reaches the desired range according to the test thermometer. If necessary, put a cover over part of the radiator and cause a restriction of the coolant flow. The reading on the water temperature indicator should agree with the test thermometer within the tolerance range of the water temperature indicator.Water Temperature Regulator Test
Remove the regulator from the engine.
Heat water in a pan until the temperature is 92°C (198°F). Stir the water in the pan. This will distribute the temperature throughout the pan.
Hang the water temperature regulator in the pan of water. The water temperature reguator must be below the surface of the water. The water temperature regulator must be away from the sides and the bottom of the pan.
Keep the water at the correct temperature for ten minutes.
After ten minutes, remove the water temperature regulator. Immediately check the distance that the water temperature regulator has opened. The distance must be a minimum of 9.53 mm (.375 inch).
If the distance is less than 9.53 mm (.375 inch), make a replacement of the water temperature regulator.