ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – 008-020   Cooling System Diagnostics

The following procedure covers common troubleshooting steps to help identify:

• Engine overheating causes. See the Initial Check section of this procedure.

NOTE: At the end of this procedure, a worksheet is provided to record any measured values taken during troubleshooting. The worksheet will help in gathering and analyzing the data.

• External and internal coolant leaks/loss. See the Pressure Test section of this procedure.
• Combustion gas leaks into the cooling system. See the Test section of this procedure.

If the coolant reaches an unacceptable level in the recovery/expansion tank, a fault code should become active that will illuminate an instrument lamp and impose a power derate. This low level is detected by a coolant level switch mounted in the coolant surge/recovery tank.

In the event of a cooling system-related malfunction, it is recommended that the coolant level switches be checked for proper operation. Refer to the OEM service manual for operational checks and repairs.

Removal and installation of the coolant level switch for diagnostics is NOT recommended. This poses a high likelihood of damage, due to the plastic construction of the switch. The coolant level switch must only be removed from the surge/recovery tank when replacing it with a new switch. Be certain not to overtighten the switch when installing. Most switches have a very low torque value, which can be found in the OEM service manual.

Coolant level switches are very susceptible to improper pH levels. For this reason, it is imperative that coolant be maintained in accordance with Cummins® Coolant Requirements and Maintenance, Bulletin 3666132.

CAUTION  Never operate the engine without a thermostat. Without a thermostat, the path of least resistance for the coolant is through the bypass to the water pump inlet. This can cause the engine to overheat.

Thermostat

There are different temperature range thermostats available, depending on the engine type and application. The part number and nominal operating temperature are stamped on the thermostat. To verify that the correct temperature range and part number thermostat is installed, make sure to reference the appropriate part information resources. Refer to Procedure 008-013 in Section 8.

Water Pump

A damaged or an incorrect water pump can lead to an engine overheating condition. To verify that the correct water pump is installed, make sure to reference the appropriate parts information resources. Refer to Procedure 008-062 in Section 8.

Belt and Belt Tensioner

A worn/incorrect belt, belt tensioner, or misaligned pulley can cause:

• Belt slip
• Belt jump or “walk off”
• Noise
• Belt breaks and shredding
• Component bearing seizure.

Refer to Procedure 008-002 or Refer to Procedure 008-080 in Section 8.

Pressure Cap

A commonly overlooked item when troubleshooting the cooling system is the radiator pressure/expansion tank cap. The cooling system is designed to use a pressure cap to prevent boiling of the coolant. An incorrect, damaged, or malfunctioning cap can result in the loss of coolant and in an engine overheating condition.

For information for pressure cap specifications, refer to the OEM service manual.

An incorrect or malfunctioning cap can also result in the loss of coolant and in an engine overheat condition.

Pressure test the radiator cap. Refer to the OEM service manual.

The pressure cap must seal within 14 kPa [2 psi] of the value stated on the cap, or it must be replaced.

Air forced through the fins of the radiator by a fan cools the coolant pumped through the radiator. Environmental debris (such as paper, straw, lint, and dust) can obstruct the fins and reduce the flow of air, which will reduce the cooling effect of the radiator.

The radiator must be inspected for bent/broken fins and coolant leaks periodically.

For maintenance, removal, or installation of the radiator, refer to the OEM service manual.

NOTE: The silicone engine coolant hose will exhibit swelling due to the elasticity of the hose.

Coolant Hoses

Collapsed or damaged coolant hoses can result in engine heating problems. Make sure to inspect all hoses for cracks, cuts, or collapsing. Replace any damaged hoses.

Inspect the coolant vent lines from the EGR cooler, cylinder head and variable geometry actuator (VGT). Make sure the lines are not pinched and that there are no sharp turns or dips in the vent lines from the engine connection point to the surge tank.

Blow shop air through the suspected lines to make sure there is no excessive restriction inside the lines.

Cooling Fan

The engine cooling fan is typically driven by a crankshaft driven belt. In some applications, the fan is located off the engine for a remote mounted cooling system.

The cooling fan is supplied by the OEM. The OEM must be contacted for any service-related information. This procedure only highlights some of the items related to cooling fans.

If the fan is belt-driven, a slipping belt will result in a slower fan speed and reduced cooling. A malfunctioning automatic belt tensioner can be the problem. Refer to Procedure 008-080 in Section 8.

Check the bearings in the fan hub and other pulleys to make sure they are not causing excessive belt vibration and slippage. Refer to Procedure 008-036 in Section 8.

The cooling fan must be inspected periodically. Check for cracks, loose rivets, and bent or loose blades.

Check the fan to make sure it is securely mounted. Tighten the capscrews, if necessary.

Only replace a damaged cooling fan with an exact equivalent cooling fan. Although same size cooling fans can appear similar, there can be differences in the blade pitch and profile.

Fan Drive

A malfunctioning fan drive can cause engine cooling problems.

Various fan drive configurations are used to determine when the fan is driven, which include:

• Direct drive – the fan is engaged all of the time
• Air engaged/disengaged clutch
• Electric/electromagnetic clutch
• Viscous clutch
• Hydraulic drive
• Crankshaft/PTO driven.

Use the following procedure for additional information on electromagnetic fan clutches supplied by Cummins Inc. Refer to Procedure 008-026 in Section 8.

For other fan clutches, refer to the OEM service manual.

Fan Shroud Assembly

A fan shroud assembly is used to direct air flow provided by the cooling fan. A missing or damaged fan shroud will reduce the amount of air flow provided by the cooling fan and can cause an engine coolant overheating condition.

Check the fan shroud for damage and/or contact with the cooling fan. Replace any damaged components. Refer to Procedure 008-038 in Section 8.

Radiator Shutters

NOTE: Make sure the air temperature sensor is functioning correctly. Check the air-operated shutter controls. Check for air leaks. Refer to the OEM service manual.

Radiator shutters are designed to control airflow across the radiator. If the shutters fail to open when needed, the engine can run hot. Inability of the shutters to close can result in too much airflow and the engine running cold.

Winter Fronts

Winter fronts can be used to reduce the engine warm up time and help maintain engine heat in cold climate locations.

The winter fronts should only cover part of the frontal area of the cooling system, leaving part of the frontal area open to air flow.

Failure to leave part of the front area open to air flow or leaving the winter fronts installed when ambient temperatures increase can lead to an engine overheating condition.

Connect an electronic service tool to the vehicle’s data link.

Turn the keyswitch to the ON position.

Monitor the coolant temperature with the electronic service tool.

If equipped with an in dash coolant temperature gauge, monitor coolant temperature with an electronic service tool and compare the cab temperature gauge reading. Replace the cab temperature gauge if it is not within the manufacturer’s specifications of the correct reading.

If the manufacturer’s specifications are not available, replace the gauge if it is not within ±3.9°C or ±7°F of the correct reading.

For vehicles equipped with temperature controlled shutters, check the coolant temperature at which the shutters open and close. Compare this value to what is stamped on the shutter control.

Cummins Inc. recommends that the shutters open at 85°C [185°F] engine coolant temperature.

If equipped with a temperature controlled cooling fan clutch, check the coolant temperature at which the fan clutch engages.

If the fan clutch engagement is controlled by a fan control on the vehicle, compare the recorded value to what is stamped on the fan control and/or reference the OEM service manual.

If the fan clutch engagement is controlled by the engine’s electronic control module (ECM), the engagement coolant temperature is a set value that can not be changed. If the fan clutch does not engage, check to make sure the fan control logic parameter is set correctly.

The ECM is capable of using either a zero (“0”) VDC or 12 VDC signal to engage the fan clutch. The exact enable logic can be selected in the Features and Parameters section of INSITE™ electronic service tool.

Cummins Inc. recommends that the fan engage at 96°C [205°F] engine coolant temperature.

If equipped with a viscous fan drive, check the coolant temperature at which the fan engages. Viscous fan clutches are typically activated by a built-in sensor behind the radiator that monitors air temperature.

NOTE: Some viscous fan drives could possibly be electronically controlled.

When the air temperature reaches a specific level, depending on the temperature setting of the sensor used, the temperature-sensing control moves an actuator that allows viscous fluid to engage the fan drive and increase the fan speed. For more information, refer to the OEM service manual.

Cummins Inc. recommends that the fan engage at 96°C [205°F] engine coolant temperature.

The operating pressure of the coolant system and the lubricating system can result in the mixing of the fluids if there is a leak between the systems:

• Cylinder head gasket
• Lubricating oil cooler, etc.

Transmission/power steering/hydraulic fluid can also leak into the coolant through radiator fluid coolers, if equipped. Refer to the OEM service manual.

Check the coolant level and fill if necessary. Refer to Procedure 008-018 in Section 8.

To aid in determining the location of the coolant leak, it may be necessary to add fluorescent tracer, Part Number 3377438, to the coolant.

Add one unit of fluorescent tracer to each 38 liters [10 gal] of coolant .

Idle the engine for 5 to 10 minutes or until normal operating temperature is reached, to allow the dye to circulate through the cooling system.

Use a high intensity black light, Part Number 3163337, or equivalent, to illuminate the dye.

CAUTION  Do not apply more than 138 kPa [20 psi] air pressure to the cooling system or damage to the water pump seal can result.

If the radiator is equipped with a pressure relief valve, plug the overflow line (1).

Install the pressure tester to the radiator fill neck or surge tank, if equipped, and apply air pressure.

The Coolant Dam™/Pressure Tester service tool, Part Number 3824319, can also be used to pressurize the cooling system. The Coolant Dam™/Pressure Tester uses shop air rather than a hand air pump.

For external coolant leaks, inspect the exterior of the engine and repair if necessary.

Pay close attention to areas around the:

• Lubricating oil cooler. Refer to Procedure 007-003 in Section 7.
• Water pump. Refer to Procedure 008-062 in Section 8.
• Air compressor head gasket. Refer to Procedure 012-014 in Section 12.
• Cup plugs. Refer to Procedure 017-002 in Section 17.
• Pipe plugs. Refer to Procedure 017-007 in Section 17.
• EGR cooler. Refer to Procedure 011-019 in Section 11.
• EGR cooler coolant line. Refer to Procedure 011-031 in Section 11.
• Variable geometry turbocharger. Refer to Procedure 010-033 in Section 10.
• Turbocharger coolant lines. Refer to Procedure 010-041 in Section 10.

For internal coolant leaks, inspect the interior of the engine. It may be necessary to remove the following components to look for signs of a coolant leak:

• Rocker lever cover. Refer to Procedure 003-011 in Section 3.
• Lubricating oil pan. Refer to Procedure 007-025 in Section 7.
• Turbocharger oil drain line. Refer to Procedure 010-045 in Section 10.

For suspected fuel in the coolant or coolant in the fuel, disconnect the fuel drain connection at the rear of the cylinder head. Refer to Procedure 006-013 in Section 6.

Coolant Pressure Check

Measure the coolant pressure at the coolant tap number 5 (1) or coolant tap number 6 (2) on the exhaust side of the cylinder head.

Coolant pressure can be affected by the following:

• Radiator pressure cap
• Debris in the cooling system
• OEM cooling options such as in-cab heaters and torque converter cooling
• Air in the cooling system
• Incorrect initial cooling system fill
• Less than 50/50 antifreeze mixture
• Engine operation at high altitude.

Record the block pressure at 60°C [140°F], closed thermostat, at high idle.

If the block coolant pressure is less than 138 kPa [20 psi] at high idle and without a pressure cap, do the following:

• Check the belt tension and condition
• Remove the water pump, inspect the impeller integrity, and check for slippage on the shaft. Refer to Procedure 008-062 in Section 8.

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

NOTE: All cab heaters and air conditioners must be turned to the OFF position, and the engine fan control must be turned to the AUTOMATIC position, if applicable.

Remove the radiator cap, and leave it off for the following test.

Install the combustion gas leak test instrument, Part Number 3822985, into the radiator cap opening.

Install the analyzer kit, Part Number 3822994.

• Red line – plugged
• Yellow line – cylinder block pressure
• Black line – water pump inlet.

Pressure Readings:

Turn the pressure selection valve to the position corresponding to the desired reading. Turn the temperature selection valve to the OFF position.

NOTE: When the cylinder block pressure reading is taken, the valve must be turned to the thermostat housing pressure location.

Start the engine and run at high idle.

Monitor the sight glass installed on the service tool throughout the test. If air is observed, finish the test, and examine the combustion leak tester. This will determine the origin of the leak.

Temperature Readings:

There will be temperature fluctuations when switching the temperature selection valve. This fluctuation is normal and is caused by temperature loss in the line. The temperature will stabilize after a few seconds.

Air in the coolant can result in loss of coolant from the overflow when the aerated coolant is hot. The heated air expands, increasing the pressure in the system, causing the cap to open.

Similarly, coolant can be displaced through the overflow if the head gasket or a crack in the cylinder head leaks compression gases into the cooling system.

Use a combustion gas tester, Part Number 3822985, or its 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.

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

Drain the coolant level down approximately 76 mm [3 in] below the radiator cap seal ledge in the radiator fill neck.

If the coolant is above this point, the coolant can contaminate the test fluid, causing the test to be ineffective.

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 certain that an airtight seal is formed between the tester and the radiator fill neck.

Start the engine and run at 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 or green anytime during the test, combustion gases are leaking into the cooling system. Discontinue the test if the color of the test fluid changes from blue to yellow or green.

If the color of the test fluid does not change from blue to yellow or green 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 or green, combustion gases are entering the cooling system and further 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 due to 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 or green is the only indication of combustion gas in the cooling system.

NOTE: Discard the tester fluid if it has indicated positive.

A positive result from the combustion gas leak tester indicates cylinder head gasket or cylinder head casting leakage. Refer to Procedure 002-004 in Section 2.

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

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant 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 that 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.

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

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

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.

NOTE: 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.

Check the color of fluid in the combustion gas leak tester. A yellow or green (not shown in the illustration) color will indicate a combustion leak. A blue color will indicate there is no leak. This information will help isolate the source of air in the cooling system, if any.

NOTE: The test kit is not sensitive enough to detect very small combustion gas leaks.

Do not rule out combustion gas leaks if the combustion gas leak test does not indicate a combustion gas leak.

Check the recorded coolant temperature when the shutters are opened. Compare this value to the stamp on the shutter control. Cummins Inc. recommends that the shutters open at 85°C [185°F].

Check the recorded coolant temperature when the fan is engaged. Cummins Inc. recommends that the fan engage at 96°C [205°F].

Compare the cab temperature gauge reading with the block temperature. Replace the cab temperature gauge if it is not within the manufacturer’s specifications for the correct reading. If no manufacturer’s specifications are available, replace the gauge if it is not within ±3.9°C [7°F] of the correct reading.

Read the recorded block pressure at 60°C [140°F]. If the block pressure is less than 138 kPa [20 psi] at high idle and without a pressure cap, check the following:

• Remove the water pump
• Inspect the impeller’s integrity, and for slippage on the shaft
• Check the belt tension and condition.

If there is a drop in block pressure of more than 34 kPa [5 psi] during the test, check the following:

• Air in the system
• Incorrect initial cooling system fill
• Less than 50/50 antifreeze mixture, or the engine is at high altitude.