Introduction
Troubleshooting can be difficult. To make a repair to a problem, refer to the possible cause and the corrective action. Also, refer to Electronic Troubleshooting for 3406E and 3456.
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.
Troubleshooting Problems
Combustion Noise
Probable Cause
Poor Quality Or Water In The Fuel – Refer to Special Instruction, SEHS7067, “Fuel Recommendations For Caterpillar Diesel Engines”. Also, Special Instruction, SEHS6947 has fuel correction factors and tables.
The Wrong Timing Position Sensor Calibration – Refer to Electronic Troubleshooting for 3406E and 3456.
Fuel Consumption Too High
Probable Cause
Poor Quality Or Water In The Fuel – Refer to Special Instructions, SEHS7067, “Fuel Recommendations For Caterpillar Diesel Engines”. Also, Special Instruction, SEHS6947 has fuel correction factors and tables.
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.
Fuel And Combustion Noise (knock) – Refer to Electronic Troubleshooting for 3406E and 3456.
Wrong Timing Position Sensor Calibration – Refer to Electronic Troubleshooting for 3406E and 3456.
Excessive Black Smoke
Probable Cause
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 Electronic Troubleshooting for 3406E and 3456.
Too Much White Smoke
Probable Cause
Engine Misfire – Refer to Electronic Troubleshooting for 3406E and 3456.
Wrong Timing Position Sensor Calibration – Refer to Electronic Troubleshooting for 3406E and 3456.
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
Too Much Blue Smoke
Probable Cause
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. Fuel can be eliminated from the crankcase by making repairs or replacements to the fuel injection lines and the nozzles.
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 the Specifications module for the specifications of the cylinder and the piston ring.
Note: High wear at low hours is normally caused by dirt. This dirt comes into the engine with the inlet air.
Low Oil Pressure
Probable Cause
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. Check the crankshaft seals and the gaskets for the engine.
Dirty Oil Filter Or Cooler Core – Check the operation of the bypass valve for the filter. As required, install new oil filter elements. Clean the oil cooler core or install a new oil cooler core. Remove the dirty oil and fill the engine with clean oil to the correct level.
Diesel Fuel In Lubricating Oil – The reason may be an internal leak or worn piston rings. 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 at the valve train. Install new parts, as needed.
Oil Pump Suction Pipe Has A Defect – Replacement of the pipe is needed.
Oil Pump Relief Valve – Clean the valve and the housing. Install new parts, as required.
Faulty Oil Pump – Replace the oil pump.
Too Much Clearance Between Camshaft And Camshaft Bearings – Inspect the bearings and the camshaft, replace as needed.
Too Much Clearance Between Crankshaft And Crankshaft Bearings – Inspect the bearings and the crankshaft journals, replace as needed.
Too Much Bearing Clearance For Idler Gear – Inspect the bearings and the idler gear, replace as needed.
Piston Cooling Jets – Inspect the piston cooling jets, replace as is needed.
Faulty Oil Pressure Gauge – Replace the oil pressure gauge.
Engine Overheating
Probable Cause
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. Low coolant level is caused by leaks or the wrong filling of the radiator. Make sure that the coolant can be seen at the low end of the filler neck on the radiator top tank when the engine is cool.
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 in order to 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. Check the radiator for the following items. These items prevent the free flow of coolant through the radiator.
- Debris
- Dirt
- Deposits on the inside of the radiator core
Loose Belts – A loose fan drive belt or a gear-driven water pump will cause a reduction in air and water flow. Tighten the belts according to the Belt Tension Chart that is shown within this module.
Faulty Hoses – Worn 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 become loose, 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.
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. Refer to Testing And Adjusting for the procedure to test water temperature regulators.
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. The shaft is then pushed back and the shaft is pulled forward. If the impeller has no damage, check the impeller clearance. The clearance between the impeller and the housing is 0.56 mm to 1.50 mm (0.022 inch to 0.059 inch).
Air In Cooling System – Air can get into the cooling system in 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 the inside cracks or faulty 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. Use a wire to hold the relief valve in the radiator cap open. 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. Use a cover on the radiator core to keep the engine at operating temperature. Place the loose end of the hose in the water bottle after five or more minutes at operating temperature. Put the bottle in the bucket of water with 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 into the cooling system. Locate the source of the air or the gas that is leaking into the cooling system and correct, as needed.
Faulty Fan – 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 Truck Manufacturer.
Insufficient Radiator Size – 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 large enough.
Not Enough Air Flow Through Radiator Because Of Restriction In Engine Compartment – The air flow through the radiator comes out of the engine compartment. Check the installation of filters, air conditioners, and similar items from preventing the free flow of air.
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 truck is used at higher altitudes. A pressurized system that is large enough to keep the coolant from boiling must be used.
Low Speed Operation of the Engine – Lugging causes the engine rpm and the fan rpm to be low. 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 less coolant flow during the high input of fuel will cause above normal 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 635 mm (25 inch) of water. If the indication is higher than the maximum permissible restriction, remove the dirt from the filter element or install a new filter element. Recheck the restriction. There must be a restriction in the inlet piping if the indication is still too high.
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 1016 mm (40 inch) of water. The system can also be checked by removing the exhaust pipes from the exhaust manifolds. Remove the exhaust pipes. Start and run the engine. Check if the problem has been corrected.
Incorrect Fuel Injection Timing – Refer to Testing And Adjusting for checking and making the necessary adjustments to the fuel injection timing.
Transmission Problems – Automatic transmissions can cause above normal operating temperatures. This happens if the transmission is out of adjustment or not working correctly. See the transmission Service Manual for the correct adjustments.
Engine Operating Temperature Below Normal
Probable Cause
Long Idle Periods – When the engine is running with no load, only a small quantity of fuel is burned.
Very Light Load – Very light loads 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 regulator that is stuck open will cause overcooling.
External Coolant Leaks
Probable Cause
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 – Pressurize the radiator or the expansion tank with the 9S-8140 Pressurizing Pump and check for leaks. Refer to Testing And Adjusting, “Cooling System – Test”.
Leaks In The Heater – Pressurize the radiator or the expansion tank with the 9S-8140 Pressurizing Pump and check for leaks. Refer to Testing And Adjusting, “Cooling System – Test”.
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.
Coolant Leaks At The Overflow Tube
Probable Cause
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 and check for leaks. Refer to Testing And Adjusting, “Cooling System – Test”.
High Engine Operating Temperature – A coolant temperature that is too high will increase the pressure. The pressure will be high enough to activate the relief valve. This will cause a coolant loss through the overflow tube. Refer to “Engine Overheating”.
Faulty Expansion Tank – 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 as the coolant heats up. 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 manufacturer.
Cylinder Head Gasket Leakage Or Crack(s) In Cylinder Head Or Cylinder Block – While the engine is running, remove the radiator cap. Look for air bubbles in the coolant. Bubbles in the coolant are a sign of probable leakage at the head gasket. Remove the cylinder head from the engine. Check the cylinder head, the cylinder walls and the head gasket surface of the cylinder block for cracks. When the head is installed, use a new head gasket, a spacer plate gasket, water seals, and O-ring seals.
Coolant Leakage Inside Engine
Probable Cause
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 in the upper surface of the cylinder head, or in 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.