Cummins N14 STC, Celect, Celect Plus – Service Manual 008-019   Cooling System – Air or Combustion Gas Test

WARNING  Do not remove the pressure cap from a hot engine. Wait until the temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

Allow the engine to cool and remove the radiator cap.

The pressure cap must make a tight seal.

Install a radiator pressure cap which has had the spring and pressure relief valve removed.

Attach a rubber hose to the radiator overflow connection.

Place the free end of the hose into a container of water.

Operate the engine at rated rpm until it reaches a temperature of 80°C [180°F] with the thermostat open.

Check for a continuous flow of air bubbles from the hose into the water container.

A continuous flow of air bubbles can be caused by one of the following:

• Fan, shutter, or heater air control thermostat valve leaking air
• An air compressor cylinder head leak.

If a continuous flow of air bubbles is present, perform the combustion gas leak test as outlined in this procedure.

If one of the air control valves or the air compressor was not the source of air entering the cooling system, perform the combustion gas leak test outlined as outlined in this procedure.

If air is not air is found in the cooling system, complete the following:

• Remove the test equipment
• Check the coolant level and fill if necessary
• Install the radiator pressure cap
• Operate the engine until it reaches a temperature of 80°C [180°F], and check for coolant leaks.

Disconnect the vehicle air supply hose to the fan, the shutter, and the heater air control valve. Install a plug into the air supply hose. If the vehicle is equipped with more than one air control valve, check only one valve at a time.

Start the engine and run for 5 minutes before testing for air in the coolant. This will allow any trapped air to purge from the system.

Repeat the test for air in the cooling system as previously described in this procedure. If air is not found in the cooling system with the air control valve(s) isolated, install a new control valve.

Disconnect the coolant supply and the return tubes from the air compressor.

Use a short piece of hose to connect the tubes together to prevent coolant loss during engine operation.

Repeat the test for air in the cooling system as previously described in the air in the cooling system test. If air is not found in the cooling system, with the air compressor isolated, repair or replace the air compressor. Refer to Procedure 012-014 in Section 12.

Disconnect the coolant supply and the return hoses from the aftercooler. Plug the hoses after removing them from the aftercooler.

The engine must be operated at rated speed and full load to detect air in the cooling system because of a defective aftercooler core.

Repeat the test for air in the cooling system as previously described.

If air is not found in the cooling system with the aftercooler isolated, install a new aftercooler. Refer to Procedure 010-001 in Section 10.

Perform the air in the cooling system test outlined in this procedure.

If the engine still fails the test for air in the cooling system with the fan, shutter controls, and the air compressor isolated from the cooling system, or if the combustion leak test is positive, pressure check the cylinder heads. Refer to Procedure 002-004 in Section 2.

If leakage is not found from the cylinder head test, check for cylinder block counterbore leaks. Refer to Procedure 001-058 in Section 1.

Remove the front pipe plug from each rocker lever housing water manifold and install a short nipple.

A 305 mm [12 in] clear tygon tube can be installed onto each nipple.

If a tube was installed fill each tube with coolant.

Remove the water pump drive belt. Refer to Procedure 008-002 in Section 8.

Run the engine and insect for bubbles percolating from the pipe nipples, or in the clear tubing if used.

A positive result from the combustion gas leak tester indicates the following:

• Cylinder liner protrusion not correct or cracked. Refer to Procedure 001-028 in Section 1.
• Cylinder head gasket, cylinder head casting leakage, or injector sleeve leaking. Refer to Procedure 002-004 in Section 2.

If bubbles do not appear, install the water pump drive belt. Refer to Procedure 008-002 in Section 8.

An optional method of testing is to use the combustion gas tester, Part Number 3822985 or equivalent, to test for combustion gases in the cooling system.

It is recommended that the cooling system contain a mixture of 50 percent antifreeze and 50 percent water during the combustion gas leak test.

The use of water only can result in a color change in the test fluid from blue to turquoise or light green during the test. This is not an indication of a combustion gas leak.

Drain the coolant level down approximately 50 mm [2 in] below the radiator cap seal ledge in the radiator fill neck.

Pour the test fluid into the combustion gas leak test instrument until it is up to the yellow fill line on the instrument.

Insert the rubber tip of the combustion gas leak test instrument into the radiator fill neck. Hold the instrument down firmly and turn back and forth to make sure that an air tight seal is formed between the tester and the radiator fill neck.

Start the engine and run at high idle for approximately 30 minutes.

Monitor the engine temperature and color of the test fluid during engine operation.

Do not allow the engine temperature to exceed 100°C [212°F] during the test.

If the color of the test fluid changes from blue to yellow anytime during the test, combustion gases are leaking into the cooling system.

Discontinue the test if the color of test fluid changes from blue to yellow.

If the color of the test fluid does not change from blue to yellow during the 30 minute test period, return the engine to low idle.

Check the test instrument to make sure it is firmly sealed in the radiator fill neck.

Insert the tip of the rubber ball into the hole in the top of the test instrument. Squeeze the rubber ball 2 to 3 minutes to draw air from the radiator through the test fluid.

If the color of the test fluid remains blue, combustion gases are not entering the cooling system.

If the color of the test fluid changes from blue to yellow, combustion gases are entering the cooling system.

Investigation is required to determine the source of the combustion leak.

As the cooling system warms up to operating temperature, air will be expelled through the combustion gas tester in the form of bubbles in the test fluid. This is because normal expansion of the coolant.

Do not mistake the presence of air bubbles in the tester as combustion gases or air leaks into the cooling system.

A change in the color of the test fluid from blue to yellow is the only indication of combustion gas in the cooling system.

A positive result from the combustion gas leak tester indicates the following:

• Cylinder liner protrusion not correct or cracked. Refer to Procedure 001-028 in Section 1.
• Cylinder head gasket, cylinder head casting leakage, or injector sleeve leaking. Refer to Procedure 002-004 in Section 2.

Discard the tester fluid if it has indicated positive.

A negative result from the combustion gas leak tester, coupled with a continuous flow of air bubbles from the previous test, indicates the following:

• Damaged fan, shutter, or heater air control valve
• Air compressor head or head gasket leakage
• Air entrained due to a bad radiator check valve or incorrect fill
• Cylinder liner protrusion not correct
• Cracked cylinder liner
• Cylinder head or gasket leakage.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

Allow the engine to cool, and remove the radiator cap.

Install a radiator pressure cap which has had the spring and the pressure relief valve removed to allow free flow from the overflow tube.

Attach a rubber hose to the radiator overflow connection.

Place the free end of the hose below the water level in a container of water.

The pressure cap must be tightly sealed in the top of the radiator fill neck.

The engine coolant temperature must be stable to perform this test. An increasing coolant temperature will give a false indication of air due to expansion of the coolant in the system.

Operate the engine at rated rpm until it reaches a temperature of 82°C [180°F].

Check for a continuous flow of air bubbles from the hose in the water container.

The cooling system diagnostic kit, Part Number 3822994, contains a sight glass and can be used to detect air or combustion gases in the cooling system.

The needle valve (1) on the coolant sight glass analyzer, Part Number 3823211, must be installed on the block pressure side of the sight glass (2).

Install coolant sight glass analyzer, Part Number 3823211, to the engine block pressure and water pump inlet pressure Compuchek® fittings.

The coolant sight glass analyzer, Part Number 3823211, must be full of water or coolant before the test is begun.

Air in the analyzer can lead to false indications of air in the cooling system.

To fill the analyzer with coolant, complete the below listed steps.

Install a male quick connect fitting, Part Numbers 3377244 or 3377245, into the water pump inlet pressure side of the analyzer.

Place the water pump inlet pressure side of the analyzer in a bucket.

Open the needle valve on the analyzer.

Install the block pressure side of the analyzer to the engine.

After the analyzer is full of coolant, disconnect the male quick connect and continue with the test.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

Loosen the radiator cap to prevent any pressure buildup in the top tank.

Start the engine.

Open the needle valve between 1/16 and 1/4 turn and look for bubbles in the sight glass.

Presence of bubbles indicates air or combustion gases in the cooling system.

Use the needle valve to control the coolant flow through the sight glass. Restricting the flow permits easier detection of air bubbles.

A continuous flow of air bubbles indicates the following:

• Entrained air because of incorrect fill or inadequate venting
• Damaged fan, shutter, or heater air control valve
• Air compressor head or head gasket leakage
• Cylinder liner protrusion not correct
• Cylinder head or gasket leakage
• Cracked cylinder liner.

If no air is found in the system, do the following:

• Remove the test equipment
• Check the coolant level and fill if necessary
• Install the radiator pressure cap
• Operate the engine until it reaches a temperature of 82°C [180°F], and check for coolant leaks.