This type of system prevents cavitation in the water pump. Cavitation is a reaction that creates low pressure bubbles that are made in liquids by mechanical forces. With this type of cooling system, creating an air pocket or a steam pocket is more difficult.
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.
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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. |
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- Check the coolant level in the cooling system. Read the two indicators for the coolant level in the top of the radiator.
- Look for leaks in the system.
- Look for bent core fins or for trash between the folded cores of the radiator. Ensure that air flow through the radiator does not have a restriction.
- Check for damage to the fan blades.
- After the engine is cool, remove the filler cap slowly.
This will allow any pressure out of the cooling system. Inspect the filler cap and the surface that seals the cap. This surface must be clean and the seal must not be damaged.
- Check the pressure relief valve. Relief pressure of the valve is 105 to 125 kPa (15 to 18 psi).
- Look for air or combustion gas in the cooling system.
Testing The Cooling System
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| Illustration 1 | g00286266 |
Boiling Point Of Water | |
Remember 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
| Tools Needed | Quantity | |
| 4C-6500 | Digital Thermometer | 1 |
| 8T-2700 | Blowby/Air Flow Indicator | 1 |
| 9U-7400 | Multitach | 1 |
| 9S-8140 | Pressurizing Pump | 1 |
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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. |
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| Illustration 2 | g00286267 |
4C-6500 Digital Thermometer | |
The 4C-6500 Digital Thermometer is used to test for any overheating conditions or for any cooling 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.
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| 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.
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| Illustration 4 | g00286276 |
6V-3121 Multitach | |
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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. |
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Check the Filler Cap
One cause for a pressure loss in the cooling system can be a defective seal on the filler cap.
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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. |
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After the engine is cool, loosen the filler cap. Then, allow the pressure out of the cooling system. Remove the filler cap.
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| Illustration 5 | g00296067 |
Typical Schematic of Filler Cap (1) Sealing surface of cap and radiator. | |
Inspect the filler cap carefully. Look for damage to the seal or to the surface that seals. Any foreign material or deposits must be removed. Check for foreign material and for deposits in the following locations:
- The filler cap
- The filler cap seal
- The sealing surface for the filler cap
Use the 9S-8140 Pressurizing Pump to test filler caps. Also, use the pressurizing pump to check the cooling system for leaks.
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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. |
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Use the following procedures for checking the filler cap:
- After the engine is cool, loosen the filler cap to the first stop. Allow the pressure out of the cooling system. Then remove the filler cap.
- Put the filler cap on the 9S-8140 Cooling System Pressurizing Pump Group .
- Look at the gauge for the exact pressure that makes the filler cap open.
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| Illustration 6 | g00403602 |
9S-8140 Cooling System Pressurizing Pump Group (1) Adapter. (2) Hose. (3) Release Valve. | |
- Compare the reading on the gauge with the filler cap's correct opening pressure.
Note: You can find the correct pressure that makes the filler cap open in two places:
- The pressure appears on the filler cap.
- The pressure appears in the Specifications.
- The pressure appears on the filler cap.
- If the filler cap is defective, install a new filler cap.
Testing The Radiator And Cooling System For Leaks
| Tools Needed | Quantity | |
| 9S-8140 | Pressurizing Pump | 1 |
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| Illustration 7 | g00286371 |
Typical Pressure Relief Valve System (1) Pressure relief valve. (2) Stud for filler cap. | |
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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. |
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Use the following procedure to check the pressure in the cooling system:
- After the engine is cool, loosen the filler cap slowly and allow pressure out of the cooling system. Then remove the filler cap from the radiator.
- Inspect the filler cap carefully.
- Look for damage, for deposits, and for any foreign materials in the following areas:
- The filler cap seal
- The filler cap's sealing surface
- The filler cap's surface
- The filler cap seal
- Remove any foreign material from the cap and any deposits from the cap.
- Any foreign material or deposits on the surface that seals must be removed.
- Look for damage, for deposits, and for any foreign materials in the following areas:
- Ensure that the coolant level is above the top of the radiator core.
- Install the filler cap. Tighten the filler cap.
- Remove hose (5) from adapter (4) .
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| Illustration 8 | g00286374 |
9S-8140 Pressurizing Pump (3) Release valve. (4) Adapter. (5) Hose. | |
- Remove the pressure test plug for the radiator top tank.
- Install the end of the hose (5) in the hole for the pressure test plug.
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| Illustration 9 | g00513312 |
- Operate the pump until the pointer on the pressure indicator does not increase.
The highest pressure indication on the pressure indicator is the point that opens the relief valve. The correct pressure that makes the relief valve open is 105 to 125 kPa (15 to 18 psi).
- If the relief valve does not open within the pressure specification, the replacement of the relief valve is necessary.
- If the relief valve is within specifications, check the radiator for outside leakage.
- Check all connections and hoses of the cooling system for outside leakage.
The radiator and the cooling system do not have leakage if the following conditions exist:
- There is no outside leakage.
- The pressure reading on the pressure indicator stays same after a five minute period.
- There is no outside leakage.
- If the reading on the pressure indicators goes down and you do not see any outside leakage, there is leakage on the inside of the cooling system. Make the necessary repairs.
- Remove the hose (5) from the pressure test location on the radiator.
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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. |
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- Install the plug in the pressure test location.
Water Temperature Regulator Test
- Remove the water temperature regulator from the engine.
- Heat water in a pan until the temperature is 91 °C (195 °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 regulator 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 9.5 mm (.37 inch).
- If the distance is less than 9.5 mm (.37 inch), replace the water temperature regulator.