Testing & Adjusting Adhere to the following warnings when performing any tests or adjustments while the engine is running: 5 . Inspect the drive belts for the fan. 6 . Check for damage to the fan blades. 7 . Look for air or combustion gas in the cooling system. 8 . Inspect the filler cap and the surface that seals the cap. This surface must be clean. 9 . Look for a large amount of dirt in the radiator core and on the engine. 10 . Check for loose or missing fan shrouds that cause poor flow of cooling air. Cooling System Tests Remember that temperature and pressure work together. When making a diagnosis of a cooling system problem, temperature and pressure must both be checked.
Cooling system pressure will have an effect on cooling system temperatures. For an example, look at the chart to see the effect of pressure and height above sea level on the boiling (steam) point of water. W ARN I N G Work carefully around an engine that is running. Engine parts that are hot, or parts that are moving, can cause personal injury. W ARN I N G Exhaust fumes contain carbon monoxide (CO) which can cause personal injury or death. Start and operate the engine in a well ventilated area only. In an enclosed area, vent the exhaust to the outside. This engine has a pressure type cooling system. A pressure type cooling system gives two advantages.
The first advantage is that the cooling system can have safe operation at a temperature that is higher than the normal boiling (steam) point of water. The second advantage is that this type system prevents cavitation (the sudden making of low pressure bubbles in liquids by mechanical forces) in the water pump. With this type system, it is more difficult for an air or steam pocket to be made in the cooling system. The cause for an engine getting too hot is generally because regular inspections of the cooling system were not made. Make a visual inspection of the cooling system before testing with testing equipment.
Cooling System Visual Inspection W ARN I N G Do not loosen the filler cap or pressure cap on a hot engine. Steam or hot coolant can cause severe burns . 1 . After the engine is cool, loosen the filler cap (on a radiator with a pressure cap, turn it to the first stop) to let pressure out of the cooling system. Then remove filler or pressure cap. 2 . Check coolant level in the cooling system. 3 . Look for leaks in the system. 4 . Look for bent radiator fins. Be sure that air flow through the radiator does not have a restriction. G643 (E) Service Manual Chapter 3. Engine Mechanical System 52