Troubleshooting can be difficult. To make a repair to a problem, refer to the possible cause and the corrective action. Also, refer to the Troubleshooting manual for more information.
This list of problems, causes and corrections will only give an indication of the location of a possible problem. This will also list the type of repairs that are needed.
Service personnel may remember similar complaints which were corrected by a previous method of troubleshooting. A similar complaint can have a different cause.
Get a good description of the problem from the operator and/or the person that owns the vehicle. Knowing the details of the problem can save time. This will make the repair job faster and easier.
Problem 1: Loud Combustion Noise
Poor Quality Or Water In The Fuel - Find the source of contamination. Remedy the suspect source.
The Wrong Timing Position Sensor Calibration - Refer to Troubleshooting, "Timing Calibration".
Problem 2: Fuel Consumption Too High
Note: Refer to the Truck Performance Diagnostic Guide, SEBD0808, "Truck Performance Complaints" for additional information. The Truck Performance Diagnostic Guide is also used for problems that are not engine related.
MPG Measurement Errors - Follow the vehicle high fuel consumption check list:
- Correct measurement of the mileage
- Correct measurement of the amount of fuel
- Comparison to other trucks
- Different truck or engine specifications
- Different operating loads
- Different operating modes
Poor Quality Or Water In The Fuel - Find the source of contamination. Remedy the suspect source.
Fuel System Leaks - Inspect the fuel system for leaks. As needed, make repairs or replacements.
Excess Idle Time - The engine should be shut off when the engine is not active.
Excess Road Speed Or Operation At High Engine Speeds - Reduce road speed and follow progressive shifting driving guidelines.
Excess Wind Drag - Decrease the gap between the cab and the trailer. Add an air deflector.
Brakes Dragging - Adjust or repair the brakes.
Fuel And Combustion Noise (knock) - Refer to Troubleshooting, "Engine Misfires, Runs Rough, or Is Unstable" for more information.
Wrong Timing Position Sensor Calibration - Refer to Troubleshooting, "Timing Calibration" for more information.
Problem 3: Too Much Black Or Gray Smoke
Not Enough Air For Combustion - Check for a plugged air cleaner element or for blockage in the air lines. Refer to Testing And Adjusting for the procedures to check inlet manifold pressure and aftercooler core leakage.
Wrong Timing Position Sensor Calibration - Refer to Troubleshooting, "Timing Calibration".
Problem 4: Too Much White Smoke
Too Much Oil In The Engine - Do not put too much oil in the crankcase. If the oil level in the crankcase increases during engine operation, check for fuel in the crankcase.
Engine Misfires Or Runs Rough - Refer to the items that are listed in the "Problem 3: Too Much Black Or Gray Smoke" section. Refer to Troubleshooting, "Engine Misfires, Runs Rough, or is Unstable" for more information.
Wrong Timing Position Sensor Calibration - Refer to Electronic Troubleshooting, "Timing Calibration" for more information.
Coolant In The Combustion System - White smoke can also be caused from the following problems.
- Coolant in the combustion chamber
- A cracked cylinder head
- A cracked cylinder liner
- A faulty cylinder head gasket
Problem 5: Too Much Blue Smoke
Failed Turbocharger Oil Seal - Check the inlet manifold and the aftercooler core for oil. The turbocharger should be repaired or replaced.
Worn Valve Guides - See the Specifications module for the maximum permissible wear of the valve guides.
Worn Piston Rings - Worn piston rings and/or cylinder walls can be the cause of blue smoke and a loss of compression. Make a visual inspection of the cylinder walls and the piston rings. If necessary, measure the cylinder walls and the piston rings. Refer to Specifications, "Piston and Rings" for the specifications of the piston ring. Refer to Specifications, "Cylinder Liner" for the specifications of the cylinder liner.
Note: High wear at low mileage is normally caused by dirt. This dirt comes into the engine with the inlet air.
Problem 6: Engine Has Low Oil Pressure
Low Engine Oil Level - Check the engine oil level and fill to the proper level.
Oil Leaks - Check for a loose oil filter or for loose oil supply lines.
Dirty Oil Filter Or Cooler - Check the operation of the bypass valve for the filter. As required, install new oil filter elements. Clean the oil cooler or install a new oil cooler. Remove the dirty oil and fill the engine with clean oil to the correct level.
Diesel Fuel In Lubricating Oil - Find the location of the diesel fuel leak into the lubrication oil. Make repairs, as needed. Remove any oil that contains diesel fuel. Install new oil filters and fill the engine with clean oil to the correct level.
Too Much Clearance Between Rocker Arm Shaft And Rocker Arms - Check for the correct lubrication in the valve train. Install new parts, as needed.
Suspect Suction Tube for the Oil Pump - Replacement of the Tube is needed.
The Relief Valve for the Oil Pump Does Not Operate Correctly. - Clean the valve and the housing. Install new parts, as required.
The Oil Pump Has A Defect. - Make a repair or a replacement of the oil pump, as needed.
Too Much Clearance Between Crankshaft And Crankshaft Bearings - Inspect the bearings and the crankshaft journals. Make a repair or a replacement, as needed.
Too Much Bearing Clearance For Idler Gear - Inspect the bearings and make replacements, as needed.
Piston Cooling Jets Are Not Installed - Install the piston cooling jets.
Faulty Oil Pressure Gauge - Replace the oil pressure gauge.
Low Coolant Level - A sufficient amount of coolant will not go through the engine and the radiator if the coolant level is too low. This lack of coolant will not take enough heat from the engine. There will be insufficient radiator coolant flow. The heat will not be released into the cooling air. Once the engine has cooled, make sure that the coolant can be seen at the low end of the fill neck that is on the radiator top tank.
Faulty Temperature Gauge - A temperature gauge which does not work correctly will not show the correct temperature. A temperature gauge can show that the coolant temperature is too hot. This can happen even when other conditions are normal. Install a gauge that is in working order or check the cooling system with the 4C-6500 Digital Thermometer.
Dirty Radiator - Check the radiator for debris between the fins of the radiator core which prevents free air flow through the radiator core.
Loose Belts - Tighten the belts according to the Belt Tension Chart. Refer to Specifications, "Belt Tension Chart".
Suspect Hoses - Suspect hoses with leaks can normally be seen. Hoses that have no visual leaks can collapse during operation. This will cause a restriction in the flow of coolant. Hoses become soft and/or get cracks after a period of time. Refer to Operation and Maintenance Manual for the frequency for changing hoses. The inside of the hose can deteriorate, and the loose particles can cause a restriction in the flow of coolant.
Shunt Line Restriction - A restriction of the shunt line from the radiator top tank to the engine water pump will cause a reduction in the water pump efficiency. A shunt line that is not correctly installed will also cause a reduction in the water pump efficiency. The result will be low coolant flow and overheating.
Shutters Not Opening Correctly - Check the opening temperature of the shutters. Also verify that the fan control switches or the viscous fans are operating correctly.
Faulty Water Temperature Regulator (Thermostat) - Above normal heating can be caused by a regulator that does not open or a regulator that opens part of the way.
Faulty Water Pump - A water pump with a loose impeller does not pump enough coolant for correct engine cooling. A loose impeller can be found by removing the water pump. Push the shaft toward the back and then pull the shaft in a forward direction. If the impeller has no damage, check the impeller clearance. The clearance between the impeller and the housing is
Air In Cooling System - Air can get into the cooling system in many different ways. The most common causes are the following causes.
- Filling the cooling system incorrectly
- Combustion gas that leaks into the system
Combustion gas can get into the system through cracks or through bad cylinder head gaskets. Air in the cooling system causes a reduction in coolant flow and bubbles in the coolant. Air bubbles hold coolant away from engine parts. This will prevent heat flow. Air in the cooling system can be found by the BOTTLE TEST. The test is made by using the following equipment.
- A one pint bottle
- A bucket of water
- A hose that will fit the end of the overflow pipe of the radiator
The cooling system should be filled correctly before testing. Install the radiator cap and tighten the radiator cap. Place the hose over the end of the overflow pipe. Start the engine. Operate the engine at high idle rpm for a minimum of five minutes after the engine is at normal operating temperature. After five or more minutes at operating temperature, place the loose end of the hose in the bottle that is filled with water. Put the bottle into the bucket of water. Place the top of the bottle in the down position. If the water gets out of the bottle in less than forty seconds, there is too much exhaust gas leakage in the cooling system. Locate the source of the air or the gas that is leaking into the cooling system and correct, as needed.
Wrong Fan, Fan Or Fan Shroud Not In Correct Position - A reduction or a loss of air flow through the radiator can be caused by a wrong fan, a fan in the wrong position or a shroud in the wrong position. The fan must be large enough to send air through most of the area of the radiator core. Make sure that the fan size, the fan shroud, and the position of the fan and shroud are according to the recommendations of the OEM.
Radiator Too Small - The area of a small radiator is not large enough to release heat into the cooling air. This will cause the engine to run at higher than normal temperatures. Make sure that the size of the radiator is according to the recommendations of the OEM.
Not Enough Air Flow Through Radiator Because Of Restriction In Engine Compartment - The air flow through the radiator comes out of the engine compartment. Make sure that the filters, the air conditioner, and similar items are not installed in a way that prevents the free flow of air into the engine compartment and out of the engine compartment.
High Outside Temperature - The outside temperature can be too high for the rating of the cooling system. There is not enough temperature difference between the outside air and the coolant temperature. To receive better cooling, use the vehicle in a lower gear.
Operating At High Altitude - The cooling capacity of the cooling system goes down as the vehicle is used at higher altitudes. A pressurized system that is large enough to keep the coolant from boiling must be used.
Engine Used In A Lug Condition - Lugging causes the engine rpm and the fan rpm to be low. The load on the engine causes the engine to lug when the vehicle is used in a gear that is too high for the engine rpm. The engine rpm will not increase even though the accelerator pedal is pushed down. Lugging also occurs when the vehicle is used in a gear and the engine rpm goes down with the accelerator pedal at maximum travel. This low rpm causes a reduction in air flow through the radiator. This also causes a reduction in the flow of coolant through the system. The combination of less air and of less coolant flow during the high input of fuel will cause abnormal heating of the engine.
Air Inlet Restriction - Higher cylinder temperatures can be caused by a restriction of the air that is coming into the engine. Heat that is an above normal amount must be transferred to the cooling system. A restriction can be checked with a water manometer or a vacuum gauge (inches of water). Connect the gauge to the engine air inlet between the air cleaner and the inlet to the turbocharger. Install the gauge. Run the engine at full load rpm and check the restriction. The maximum restriction of the air inlet is
Exhaust Restriction - A restriction in the exhaust system causes high cylinder temperatures. Heat that is an above normal amount must be transferred to the cooling system. Check for damage to piping or for a bad muffler. If no damage is found, check the system for back pressure from the exhaust (the pressure difference measurement between the exhaust outlet and the atmosphere). The back pressure must not be more than
Fuel Injection Timing Not Correct - Refer to Testing and Adjusting, "Gear Group (Front) - Time" for checking and making the necessary adjustments to the fuel injection timing.
Transmission Problems - Power shift transmissions or automatic transmissions that are cooled by the engine cooling system can cause abnormal heating. This happens if the transmission is out of adjustment or not working correctly. See the transmission Service Manual for the correct adjustments.
Long Idle Periods - When the engine is running with no load, only a small quantity of fuel is burned. Therefore, the heat from the engine is removed too fast. The check valve in the vent line may be missing, or the orifice in the vent line may be missing. When the check valve or the orifice is missing, too much heat is removed from the engine.
Very Light Load - Very light loads, a very slow speed or downhill travel can cause overcooling. This overcooling is caused by the low heat input of the engine. The installation of shutters helps to correct this condition.
Faulty Water Temperature Regulator (thermostat) - A water temperature regulator that is stuck open can cause overcooling. Overcooling also occurs when the water temperature regulator is stuck between the following positions: open position and closed position. Coolant leaks that are around the water temperature regulator can cause overcooling. An example would be a vent line leak.
Problem 9: Coolant Leaks Outside Of Engine
Leaks In Hoses Or Connections - Check all hoses and connections for visual signs of leakage. If no leaks are seen, look for damage to hoses or loose clamps.
Leaks In The Radiator And/Or Expansion Tank - Apply pressure to the radiator or the expansion tank with the 9S-8140 Pressurizing Pump. Check for leaks. Refer to Testing And Adjusting, "Testing Radiator And Cooling System For Leaks".
Leaks In The Heater - Apply pressure to the radiator or to the expansion tank with the 9S-8140 Pressurizing Pump. Check for leaks. Refer to Testing And Adjusting, "Testing Radiator And Cooling System For Leaks".
Leaks In The Water Pump - Check the water pump for leaks before starting the engine. Start the engine and look for leaks. If the water pump leaks, repair the water pump or install a new water pump.
Cylinder Head Gasket Leakage - Look for leaks along the surface of the cylinder head gasket. Install a new head gasket if leaks are visible.
Problem 10: Coolant Leaks At The Overflow Tube
Faulty Pressure Cap Or Relief Valve - Check the sealing surfaces of the pressure cap and the radiator. Make sure that the cap is sealing correctly. Check the opening pressure and the sealing ability of the pressure cap or relief valve with the 9S-8140 Pressurizing Pump. Check for leaks. Refer to Testing And Adjusting, "Testing Radiator And Cooling System For Leaks".
Engine Runs Too Hot - A coolant temperature that is too high will cause the pressure to be high. The high pressure separates the cap from the sealing surface. This will cause a coolant loss through the overflow tube. Refer to "Problem 7: Engine Overheating".
Expansion Tank Overfilled - The expansion tank can be part of the radiator or the expansion tank can be installed separately from the radiator. The expansion tank must be large enough to hold the expansion of the coolant. The coolant gets warm and the coolant has sudden changes in pressure. Make sure that the expansion tank is installed correctly. Make sure that the expansion tank is the correct size according to the recommendations of the OEM.
Problem 11: Coolant Leakage Inside Engine
Cylinder Head Gasket Leakage - If the cylinder head gasket leaks between a water passage and an opening into the crankcase, coolant will get into the crankcase.
Crack(s) In Cylinder Head - Cracks that are in the upper surface of the cylinder head (an area between a water passage and an opening into the crankcase) can allow coolant to get into the crankcase.
Crack(s) In Cylinder Block - Cracks in the cylinder block between a water passage and the crankcase will allow coolant to get into the crankcase.
Cylinder Liner Pitting - Poor cooling system maintenance can cause pitting of the cylinder liners. Pitting of the cylinder liners can allow coolant into the combustion chamber or the crankcase.