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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.
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.
Check the coolant level in the cooling system. Read the two indicators for the coolant level in the top of the radiator.Note: Inspect the water pump seals. A small amount of coolant leakage that is across the surface of the seals is normal. The leakage is required to provide lubrication for this type of seal. A hole is provided in the water pump housing. This hole allows coolant/seal lubricant to drain from the pump housing. Intermittent leakage of small amounts of coolant from this hole is not an indication of water pump seal failure. Replace the water pump seals when the following conditions exist: large amount of leakage and constant flow of coolant from the water pump housing.
Look for leaks in the system.
Make sure that air flow through the radiator does not have a restriction. Look for bent core fins between the folded cores of the radiator. Also, look for trash between the folded cores of the radiator.
Inspect the drive belts for the fan.
Check for damage to the fan blades.
Look for air or combustion gas in the cooling system.
Inspect the filler cap, and check the surface that seals the filler cap. This surface must be clean.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 the 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    
8T-2700     Blowby/Air Flow Indicator     1    
9S-8140     Pressurizing Pump     1    
6V-3121     Multitach     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 g00300241
4C-6500 Digital Thermometer The 4C-6500 Digital Thermometer is used in the diagnosis of overheating conditions or in the diagnosis of overcooling conditions. 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.
Illustration 3 g00286269
8T-2700 Blowby/Air Flow Indicator The 8T-2700 Blowby/Air Flow Indicator is used to check the air flow through the radiator core. Refer to the testing procedure in Special Instruction, SEHS8712.
Illustration 4 g00300249
6V-3121 Multitach The 6V-3121 Multitach is used to check the fan speed. Refer to the testing procedure in Special Instruction, SEHS7807.Checking the Filler Cap
Illustration 5 g00286369
9S-8140 Pressurizing Pump The 9S-8140 Pressurizing Pump is used to test the filler caps. This pressurizing pump is also used to pressure test the cooling system for leaks.
Personal injury can result from hot coolant, steam and alkali.At operating temperature, engine coolant is hot and under pressure. The radiator and all li