0318397 JOHNSON PLATE, Thermostat housing

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.
At operating temperature, the engine coolant is hot and under pressure.Steam can cause personal injury.Check the coolant level only after the engine has been stopped and the filler cap is cool enough to touch with the bare hand.Remove the filler cap slowly to relieve pressure.Cooling system conditioner contains alkali. Avoid contact with skin and eyes to prevent personal injury.
Check the coolant level in the cooling system.
Look for leaks in the system.Note: The seals of the water pump will leak. A small amount of coolant leakage across the surface of the face type 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 the coolant 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 only if a large amount of leakage or a constant flow of coolant is observed draining from the water pump housing.
Look for leaks or restrictions in the expansion tank and raw water heat exchanger.
Inspect the raw water pump and inspect the inlet screens.
Check for damage or check for restrictions.
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    
9S-8140     Pressurizing Pump     1    
9U-7400     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 problems or in the diagnosis of overcooling problems. This group can be used to check temperatures in several different parts of the cooling system. Refer to the testing procedure in Operation and Maintenance Manual.
Illustration 3 g00300249
9U-7400 Multitach The 9U-7400 Multitach is used to check the fan speed.The Multitach can measure engine rpm from a magnetic pickup. This magnetic pickup is located in the flywheel housing. The magnetic pickup also uses the ability to measure engine rpm from visual engine parts that are rotating. Refer to the testing procedure in Special Instruction, SEHS7807.Checking the Filler Cap
Illustration 4 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.
Table 2
Tools Needed     Quantity    
9S-8140     Pressurizing Pump     1    
At operating temperature, the engine coolant is hot and under pressure.Steam can cause personal injury.Check the coolant level only after the engine has been stopped and the filler cap is cool enough to touch with the bare hand.Remove the filler cap slowly to relieve pressure.Cooling system conditioner contains alkali. Avoid contact with skin and eyes to prevent personal injury.