This type of system prevents cavitation in the water pump. Cavitation is bubbles in liquids that are created by mechanical forces. With this type of cooling system, an air pocket or a steam pocket becomes more difficult to create in the cooling system.
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.
 |
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. |
 |
- 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.
- 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
 | |
| 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 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 |
| 9U-7400 | Multitach | 1 |
| or | or | |
| 1U-6602 | Tachometer Group | |
|
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 | g00286267 |
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 Operating Manual, NEHS0554.
 | |
| 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.
 | |
| Illustration 4 | g00286276 |
9U-7400 Multitach | |
The 9U-7400 Multitach is used to check the fan speed. Refer to the testing procedure in Operator Manual, NEHS0605 .
The 9U-7400 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.
 | |
| Illustration 5 | g00296064 |
The 1U-6602 Tachometer Group is a phototach for general use. The 1U-6602 Tachometer Group is a phototach, so this tachometer only registers basic input frequency on any visible, rotating part. The basic input frequency equals one revolution per piece of reflective tape. The 1U-6602 Tachometer Group does not replace the 9U-7400 Multitach .
Checking the Filler Cap
 | |
| Illustration 6 | 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.
|
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. |
|
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 |
 | |
| Illustration 7 | 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.
| | |
| Illustration 8 | g00286369 |
9S-8140 Pressurizing Pump | |
|
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. |
|
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:
- 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.
|
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. |
|
- Make sure that the coolant level is above the top of the radiator core.
- Put the 9S-8140 Pressurizing Pump onto the radiator.
 | |
| Illustration 9 | 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 | Digital Thermometer | 1 |
| or | or | |
| 2F-7112 | Thermometer | |
| 8J-7844 | Adapter Fitting | 1 |
| 3K-0360 | O-Ring Seal | 1 |
| 4M-5317 | Terminal Bushing | 1 |
| or | or | |
| 5P-2720 (1) | Probe Adapter Group | |
| ( 1 ) | Used in conjunction with a 5P-2718 Pressure Probe |
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).
 | |
| Illustration 10 | g00433020 |
(1) Plug. (2) Water temperature regulator housing. | |
Remove the plug (1) . Install one of the following thermometers:
A temperature indicator of known accuracy can also be used to make this check.
|
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. |
|
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.
Water Temperature Regulator Test
- Remove the regulator (regulators) from the engine.
Note: An option is available for both single regulators and dual regulators. For dual regulators, both of these types of regulators must be installed. You must install both of these types of regulators, or the engine's performance will be adversely affected.
- Heat water in a pan until the temperature is 94°C (202°F). Stir the water in the pan. This allows the temperature to radiate throughout the pan.
- Hang the water temperature regulator (regulators) 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 (regulators). Immediately check the distance that the water temperature regulator (regulators) has opened.
Refer to the Specifications, "Water Temperature Regulator" for more information about the minimum distance for openings on the water temperature regulator (regulators).
If the distance is less than the amount listed in the manual, replace the water temperature regulator.
Water Pump Pressure Check
| Tools Needed | Quantity | |
| 6V-7775 | Air Pressure Gauge | 1 |
| 8J-7844 | Adapter Fitting | 1 |
| 3K-0360 | O-Ring Seal | 1 |
| 5P-2725 | Probe Adapter Group | 1 |
| 5P-2718 | Pressure Probe (1) | 1 |
| 5P- 4487 | Adapter | 1 |
| 5P-2720 | Probe Adapter Group | 1 |
| 5P-2718 | Pressure Probe (1) | 1 |
| ( 1 ) | If port (1) is used, two tools are required. |
 | |
| Illustration 11 | g00433021 |
(1) Port (alternate heater supply). (2) Port (engine diagnosis). (3) Ports (Heater return line). | |
The pressure rise is the difference between inlet pressure and outlet pressure. The pressure rise indicates if the water pump operates correctly. Port (1) and Port (2) represent the water pump outlet pressure. Ports (3) represent the water pump inlet pressure.
To measure the pressure rise, compare inlet pressure with outlet pressure. Calculate the difference between the pressure in these ports. The pressure rise must add up to a minimum of 80 kPa (12 psi) under both of the following conditions:
- The engine is at operating temperature.
- The engine operates at full load condition.