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.
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
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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 |
| 9S-8140 | Pressurizing Pump | 1 |
| 6V-3121 | Multitach | 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 | 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.
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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 | 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
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| 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.
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Personal injury can result from hot coolant, steam and alkali. At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns. Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand. Cooling System Conditioner contains alkali. Avoid contact with skin and eyes. |
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One cause for a pressure loss in the cooling system can be a defective seal on the radiator filler cap.
| Tools Needed | Quantity | |
| 9S-8140 | Pressurizing Pump | 1 |
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| Illustration 6 | g00296067 |
Typical Schematic of Filler Cap (1) Sealing surface of both filler cap and radiator | |
After the engine cools, loosen the filler cap. Slowly release the pressure from the cooling system. Then, remove the filler cap.
Carefully inspect the filler cap. Look for any damage to the seals and to the sealing surface. Inspect the following components for any foreign substances:
- Filler cap
- Seal
- Surface for seal
Remove any deposits that are found on these items, and remove any material that is found on these items.
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Personal injury can result from hot coolant, steam and alkali. At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns. Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand. Cooling System Conditioner contains alkali. Avoid contact with skin and eyes. |
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To check for the amount of pressure that opens the filler cap, use the following procedure:
- Carefully remove the filler cap from the radiator.
- Put the filler cap on the 9S-8140 Pressurizing Pump .
- Look at the gauge for the exact pressure that opens the filler cap.
- Compare the gauge's reading with the correct pressure that should open the filler cap:
Note: The correct pressure that makes the filler cap open is printed on the filler cap.
- If the filler cap is defective, replace the filler cap.
Testing The Radiator And Cooling System For Leaks
| Tools Needed | Quantity | |
| 9S-8140 | Pressurizing Pump | 1 |
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.
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Personal injury can result from hot coolant, steam and alkali. At operating temperature, engine coolant is hot and under pressure. The radiator and all lines to heaters or the engine contain hot coolant or steam. Any contact can cause severe burns. Remove filler cap slowly to relieve pressure only when engine is stopped and radiator cap is cool enough to touch with your bare hand. Cooling System Conditioner contains alkali. Avoid contact with skin and eyes. |
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- Make sure that the coolant level is above the top of the radiator core.
- Put the 9S-8140 Pressurizing Pump onto the radiator.
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| Illustration 7 | g00286374 |
9S-8140 Pressurizing Pump | |
- Take the pressure reading on the gauge to 20 kPa (3 psi) more than the pressure on the filler cap.
- Check the radiator for leakage on the outside.
- Check all connection points for leakage, and check the hoses for leakage.
The cooling system does not have leakage only if the following conditions exist:.
- You do NOT see any outside leakage.
- The reading remains steady after five minutes.
The inside of the cooling system has leakage only if the following conditions exist:
- The reading on the gauge goes down.
- You do NOT observe any outside leakage.
Make any repairs, as required.
Test For The Water Temperature Gauge
| Tools Needed | Quantity | |
| 4C-6500 or 2F-7112 |
Digital Thermometer or Thermometer |
1 |
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| Illustration 8 | g00300299 |
Water Temperature Connection (1) Water temperature regulator housing. (2) Plug. (3) Plug. | |
Check the accuracy of the water temperature indicator or water temperature sensor if you find either of the following conditions:
- The engine runs at a temperature that is too hot, but a normal temperature is indicated. A loss of coolant is found.
- The engine runs at a normal temperature, but a hot temperature is indicated. No loss of coolant is found.
Coolant temperature can also be read on the display screens of the Electronic Service Tool (ECAP or ET).
Remove one of the plugs (2) or (3). Install one of the following thermometers:
A temperature indicator of known accuracy can also be used to make this check.
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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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| Illustration 9 | g00300300 |
Water Temperature Gauge | |
Start the engine. Run the engine until the temperature reaches the desired range according to the test thermometer. If necessary, place a cover over part of the radiator in order to 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.
| Pointer Position |
Test Thermometer °C |
Test Thermometer °F |
| 1 | 65 to 77 | 150 to 170 |
| 2 | 99 to 103 | 210 to 218 |
Water Temperature Regulator Test
- Remove the regulator from the engine.
- Heat water in a pan until the temperature is 98°C (208°F). Stir the water in the pan. This allows the temperature to radiate 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.
- If the distance is less than 9.50 mm (.3740 inch), the regulator needs to be replaced.
If the distance is at least 9.50 mm (.3740 inch), the regulator is in working order.