This type of system prevents cavitation in the water pump. Cavitation is the forming of low pressure bubbles in liquids that are caused by mechanical forces.
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| Illustration 1 | g00286266 |
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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 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.
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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. |
The coolant level must be to the correct level in order to check the coolant system. The engine must be cold and the engine must not be running.
After the engine is cool, loosen the pressure cap in order to relieve the pressure out of the cooling system. Then remove the pressure cap.
| Tools Needed | ||
| Part Number | Part Name | Quantity |
| 4C-6500 | Digital Thermometer | 1 |
| 8T-2700 | Blowby/Air Flow Indicator | 1 |
| 9S-8140 | Pressurizing Pump | 1 |
| 9U-7400 | Multitach Tool Group | 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 |
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4C-6500 Digital Thermometer | |
The 4C-6500 Digital Thermometer is used in the diagnosis of overheating conditions and in the diagnosis of overcooling conditions. This group can be used to check temperatures in several different parts of the cooling system. Refer to Operating Manual, NEHS0554, " 4C-6500 Digital Thermometer Group" for the testing procedure.
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| Illustration 3 | g00286269 |
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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 Special Instruction, SEHS8712, "Using the 8T-2700 Blowby/Air Flow Indicator" for the test procedure for checking blowby.
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| Illustration 4 | g00286276 |
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9U-7400 Multitach | |
The 9U-7400 Multitach Tool Group is used to check the fan speed. Refer to Operating Manual, NEHS0605, " 9U-7400 Multitach Tool Group " for the testing procedure.
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| Illustration 5 | g00286369 |
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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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| Illustration 6 | g00439083 |
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1U-7297 Coolant/Battery Tester or 1U-7298 Coolant/Battery Tester | |
Check the coolant frequently in cold weather for the proper glycol concentration. Use either the 1U-7297 Coolant/Battery Tester or the 1U-7298 Coolant/Battery Tester in order to ensure adequate freeze protection. The testers are identical except for the temperature scale. The testers give immediate, accurate readings. The testers can be used for antifreeze/coolants that contain ethylene or propylene glycol.
Making the Correct Coolant Mixtures
Adding pure antifreeze as a makeup solution for the cooling system top-off is an unacceptable practice. Adding pure antifreeze increases the concentration of coolant in the cooling system. This increases the concentration of the dissolved solids and the undissolved chemical inhibitors in the cooling system. Add the antifreeze and water mixture in the same concentration as your cooling system. The following chart assists in determining the correct concentration of antifreeze and water. Refer to Operation and Maintenance Manual, "General Coolant Information".
| Coolant Concentrations | |
| Temperature | Concentration |
| Protection to |
30% antifreeze and 70% water |
| Protection to |
40% antifreeze and 60% water |
| Protection to |
50% antifreeze and 50% water |
| Protection to |
60% antifreeze and 40% water |
| Tools Needed | ||
| Part Number | Part Name | Quantity |
| 9S-8140 | Pressurizing Pump | 1 |
One cause for a pressure loss in the cooling system can be a damaged seal on the radiator filler cap.
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| Illustration 7 | g00296067 |
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Typical schematic of filler cap (1) Sealing surface of both filler cap and radiator | |
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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. |
To check for the amount of pressure that opens the filler cap, use the following procedure:
- After the engine cools, carefully 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.
- Install 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 reading with the opening pressure that is listed on the filler cap.
- If the filler cap is damaged, replace the filler cap.
Testing The Expansion Tank And Cooling System For Leaks
| Tools Needed | ||
| Part Number | Part Name | Quantity |
| 9S-8140 | Pressurizing Pump | 1 |
Use the following procedure in order to check the cooling system for leaks:
- 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 expansion tank.
- Ensure that the coolant level is at the proper level.
- Install the 9S-8140 Pressurizing Pump onto the expansion tanks.
- Take the pressure reading on the gauge to
20 kPa (3 psi) more than the pressure on the filler cap. - Check the expansion tank for leakage on the outside.
- Check all connection points for leakage, and check the hoses for leakage.
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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. |
The cooling system does not have leakage only if the following conditions exist:.
- You do NOT observe 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 | ||
| Part Number | Part Name | Quantity |
| 4C-6500
or 2F-7112 |
Digital Thermometer
or Thermometer |
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. |
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.
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| Illustration 8 | g00681430 |
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Typical example (1) Water manifold assembly | |
Remove a plug from water manifold assembly (1). Install one of the following thermometers in the open port:
A temperature indicator of known accuracy can also be used to make this check.
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 air flow. The reading on the water temperature indicator should agree with the test thermometer within the tolerance range of the water temperature indicator.