C-10 and C-12 Truck Engines Caterpillar


Cooling System

Usage:

C-12 1YN
This engine has a pressure type cooling system. This type of cooling system can be operated in a safe manner at a temperature higher than the normal boiling point (steam) of water.

A pressure type cooling system helps prevent cavitation in the water pump. Cavitation is the formation of air bubbles in low pressure areas in liquids. The mechanical forces that are created by the pumping action of the water pump are considered to be a common cause of cavitation. A pressure type cooling system tends to inhibit the formation of air bubbles within the cooling system. Air bubbles are the cause of air pockets, or steam pockets, which can damage the cooling system.

Visual Inspection Of The Cooling System

Cooling systems that are not regularly inspected and maintained may be the cause of increased engine temperatures. Make a visual inspection of the cooling system before you begin testing.

------ WARNING! ------

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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  1. Check the coolant level in the cooling system. Read the two level indicators for the cooling system that are in the top of the radiator.

  1. Inspect the cooling system for leaks.

    Note: A small amount of coolant leakage across the surface of the water pump seals is normal. This leakage is required in order to provide lubrication for the water pump seals. A weep hole has been machined in the water pump housing in order to allow this 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. Do not replace the water pump seals unless you find a continuous flow of coolant, or a large amount of coolant, that is leaking from the water pump housing. Refer to Disassembly and Assembly, "Water Pump" for the replacement procedure of the water pump seals.

  1. Make sure that air flow through the radiator is not restricted. Look for bent core fins between the folded cores of the radiator. Also, look for debris between the folded cores of the radiator.

  1. Inspect the fan drive belts for cracking or separation.

  1. Inspect the fan blades in order to ensure that the blades are not damaged or bent.

  1. Check the engine oil dipstick for signs of an internal coolant leak. The engine oil will have a milky appearance if contamination from the cooling system is present. If internal leakage is suspected, refer to "Testing The Radiator And Cooling System For Leaks" for instructions on pressure testing the cooling system.

  1. Look in the radiator filler neck for air bubbles or combustion gas in the cooling system.

  1. Inspect the pressure cap and the sealing surface. This surface must be clean and free of corrosion.

Testing The Cooling System




Illustration 1g00286266

Boiling point of water

Temperature and pressure work together. When a diagnosis is made of a cooling system problem, both the temperature and the 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 chart demonstrates the effect of pressure on the boiling point (steam) of water. Elevation also affects a pressure type cooling system. The chart also demonstrates this effect.

------ WARNING! ------

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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The coolant level must be within specifications prior to testing the cooling system. The engine must be cold and the engine must not be running.

Ensure that the engine is cool and loosen the pressure cap in order to relieve any pressure from the cooling system. Slowly remove the pressure cap.

The level of the coolant should not be more than 13 mm (0.5 inch) from the bottom of the filler neck. If the cooling system is equipped with a sight glass, the level of the coolant should be to the proper level on the sight glass.

Test Tools For Cooling System

Table 1
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    

------ WARNING! ------

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 2g00876179

4C-6500 Digital Thermometer

Use the 4C-6500 Digital Thermometer for the diagnosis of both overheating and 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 3g00286269

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 4g00286276

9U-7400 Multitach Tool Group

The 9U-7400 Multitach Tool Group should be used in order to check the fan speed. Refer to the testing procedure in Operator Manual, NEHS0605.




Illustration 5g00286369

9S-8140 Pressurizing Pump

The 9S-8140 Pressurizing Pump is used to test the filler cap and the cooling system for leaks.




Illustration 6g00439083

1U-7297 Coolant/Battery Tester or 1U-7298 Coolant/Battery Tester

Check the coolant solution frequently in cold weather for the proper glycol concentration with the 1U-7297 Coolant/Battery Tester or 1U-7298 Coolant/Battery Tester. The proper glycol concentration will ensure adequate freeze protection. Either of the testers can be used to check the freeze point of the coolant. 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 Antifreeze Mixtures

Adding pure antifreeze as a makeup solution for the cooling system top-off is an unacceptable practice. The addition of pure antifreeze will increase the concentration of glycol in the cooling system. As the glycol concentration increases, the concentration of dissolved solids and undissolved chemical inhibitors in the cooling system also increases. Add an antifreeze and water mixture with a freeze protection that is similar to the current concentration that is found in the system. The following chart assists in determining the proper concentration of antifreeze to use. For more information on coolant specifications, refer to the Operation and Maintenance Manual, "General Coolant Information".

Table 2
Antifreeze Concentrations    
Protection Temperature     Concentration    
Protection to
-15 °C (5.0 °F)    
30% antifreeze and 70% water    
Protection to
-23 °C (-10.0 °F)    
40% antifreeze and 60% water    
Protection to
-37 °C (-34.0 °F)    
50% antifreeze and 50% water    
Protection to
-51 °C (-60.0 °F)    
60% antifreeze and 40% water    

Checking the Filler Cap

Table 3
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.




Illustration 7g00296067

Typical schematic of filler cap

(1) Sealing surface of both filler cap and radiator

------ WARNING! ------

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.

----------------------

Ensure that the filler cap's pressure rating conforms to Caterpillar's application guidelines. For information that relates to the correct pressure rating for your application, refer to the Parts Manual.

To check for the amount of pressure that is required to open the filler cap, use the following procedure:

  1. After the engine cools, carefully loosen the filler cap. Slowly release the pressure from the cooling system and remove the filler cap.

    Carefully inspect the filler cap. Look for damage to the seals and damage to the cap's sealing surface. Inspect the following components for any foreign substances:

    • Filler cap

    • Seal

    • Surface for the seal

    Remove any deposits that are found on these items, and remove any material that is found on these items.

  1. Put the filler cap on the 9S-8140 Pressurizing Pump .

  1. Check the gauge for the exact pressure that is required to open the filler cap.

  1. Compare the gauge's reading with the specification of the filler cap:

  1. If the filler cap is damaged, replace the filler cap.

Testing The Radiator And Cooling System For Leaks

Table 4
Tools Needed    
Part Number     Part Name     Quantity    
9S-8140     Pressurizing Pump     1    

Use the following procedure to check the cooling system for leaks:

    ------ WARNING! ------

    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.

    ----------------------

  1. After the engine cools, carefully loosen the filler cap. Slowly release the pressure from the cooling system and remove the filler cap.

  1. Ensure that the coolant level is above the top of the radiator cores.

  1. Put the 9S-8140 Pressurizing Pump onto the radiator.

  1. Pressurize the cooling system to a pressure that is 20 kPa (3 psi) greater than the rated pressure of the filler cap.

  1. Check the radiator for external leakage.

  1. Check all cooling system hoses for cracking or stretching. Check all hose connections for leakage.

  1. Check for indications of coolant leakage from the water pump seal.

  1. Ensure that the water pump's weep hole is not plugged with debris.

The cooling system is not considered to have leakage if the following conditions exist:

  • The cooling system retains a constant test pressure for at least five minutes.

  • No external leakage is observed.

The cooling system may have an internal leak if the following conditions exist:

  • The cooling system does not hold the test pressure for the required five minutes.

  • Coolant has not been observed leaking from the engine.

An internal leak can also be detected by regularly scheduled oil sampling. Internal leakage of engine coolant will be indicated by a scheduled oil sampling result that indicates a positive test result for ethylene glycol in the engine oil.

Investigate the cause of coolant that has been found in the engine oil by removing the engine oil pan and investigating the cause of the leakage.

Note: If the weep hole becomes obstructed, then coolant may be forced past the water pump's gasket into the crankcase.

If an internal leak is found, it is absolutely necessary that the cause of the leakage be investigated prior to engine repair. If the cause of the leak is not determined, repairing the leakage may not resolve the problem.

Ensure that the cause of any internal leakage is addressed prior to repairing the leak.

Make any repairs, as required.

Test For The Water Temperature Gauge

Table 5
Tools Needed    
Part Number     Part Name     Quantity    
4C-6500 or 2F-7112     Digital Thermometer
or
Thermometer    
1    

------ WARNING! ------

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.

----------------------

------ WARNING! ------

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 engine coolant temperature gauge and coolant temperature sensor if you find either of the following conditions:

  • The engine runs at a temperature that is too hot, but the coolant gauge indicates a normal temperature. 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.

You can also use an Electronic Service Tool such as CAT ET to read the engine coolant temperature.




Illustration 8g00438983

Test location

(1) Plug

Remove the plugs (1). Install one of the following thermometers:

Any 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 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

    ------ WARNING! ------

    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.

    ----------------------

  1. Remove the water temperature regulator from the engine.

  1. Heat water in a pan until the temperature of the water is 98°C (208°F). Stir the water in the pan. This allows the temperature to radiate throughout the pan.

  1. Use a piece of wire to suspend the water temperature regulator in the pan of hot 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.

  1. Keep the water at the correct temperature for ten minutes.

  1. After ten minutes, remove the water temperature regulator. Check the operation of the water temperature regulator by measuring the regulator's opening.

  1. If the distance is less than 10.4 mm (0.41 inch), replace the water temperature regulator.

    Refer to the Specifications, "Water Temperature Regulator" for more information about the minimum distance for openings on the water temperature regulator.

Water Pump Pressure Check

Table 6
Tools Needed    
Part Number     Part Name     Quantity    
6V-7775     Air Pressure Gauge     1    



Illustration 9g00439003

Water pump group

(1) Plug

(2) Coolant temperature sensor

(3) Water manifold assembly

(4) Water outlet

(5) Temperature regulator housing

(6) Bypass line

(7) Water pump

(8) Plug

------ WARNING! ------

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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Water pump outlet pressure can be checked on water manifold assembly (3) next to coolant temperature sensor (2). This check will determine if the water pump is operating correctly.

Remove plug (1) from water manifold assembly (3). Install the 6V-7775 Air Pressure Gauge in the port and measure the pump pressure. The water pump pressure should be 100 to 125 kPa (15 to 18 psi).

A differential pressure can be measured between plug (1) on water manifold assembly (4) and plug (8) on the inlet side of water pump (7). Ensure that the differential pressure is within specifications.

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