| Symptom | Possible Sources | Action |
| Loss of oil | * Oil leaks on components that are either coated in oil or have always oil leaks on ancillary components. | * Look for evidence of oil leaks on components. Use a ultraviolet (UV) leak tester if oil leak is not evident. Install new gaskets or components as required. |
| * Internal or external leak at the oil cooler. | * Check the coolant expansion tank for oil film on the coolant surface. Install a new oil cooler or oil cooler gasket. |
| * Leak at the crankshaft oil seal or incorrect front cover alignment. | * Install a new oil seal. * Align the front cover. |
| * Leaks from oil carrying components or basic engine. | * Locate cracks in oil-carrying components of the basic engine by means of a UV leak test, and renew the relevant components or seals. |
| Oil consumption | * Use of the wrong type of engine oil. | * Determine the last type of engine oil used (refer of the latest invoice of oil receipt) and compare with the specification. Change the engine oil. |
| * Faulty positive crankcase ventilation system. - Hoses or ventilation or breather valves are blocked. This causes excessive pressure in the crankcase which causes more oil to enter the combustion chamber. - Crankcase ventilation oil separator is faulty and engine oil can enter the combustion chamber through the intake manifold. | * |
| * Turbocharger seals (only diesel engines). | * |
| * Damaged gaskets or mating surfaces. - Cylinder head gasket is damaged or mating face are warped. - Valve stem oil seals are worn and engine oil can enter the combustion chamber between the valve stem and the valve stem guide. | * Check the gaskets and mating surfaces for damage. - Remove the cylinder head. Check the mating faces, cylinder head gaskets and the evenness of the cylinder head and engine block mating faces. - |
| * Piston ring or cylinder liner wear. | * Install new components as necessary. |
| * Damaged cylinder liners or excessive clearance of engine components. - Pistons - Piston rings (clearance in groove and end gap) - Cylinder liners | * Check the running surfaces and clearances of the individual engine components, and renew if necessary. Renew the cylinder block if necessary. - Pistons - Piston rings - Cylinder liners |
| Coolant consumption | * Cooling system components. | * |
| * Exhaust gas recirculation (EGR) cooler (only diesel engine). | * Install a new EGR cooler. |
| * Oil cooler. | * Install a new oil cooler. |
| * Damaged gaskets or warped mating faces. | * |
| * Cracks or fractures in engine components surrounded by coolant, such as cylinder liners and cylinder head combustion chamber. | * Determine the damaged engine component and install a new component. |
| Engine will not crank | * Battery or cables. | * |
| * Starter motor or cables. | * |
| Engine cranks but will not start | * Fuel tank is empty. | * Check the fuel level. |
| * Water in fuel (only diesel engine). | * |
| * Fuel filter blocked. | * |
| * Engine intake air system. | * |
| * Glow plug faulty. | * |
| * Engine management system. | * |
| * Ignition system (petrol engines only). | * |
| * Incorrect valve timing. | * |
| * Broken or damaged timing chain or sprocket (only petrol engines). | * |
| * Ripped or damaged timing belt (only diesel engine). | * |
| Very poor power output or fuel consumption too high or engine running rough | * Fuel system. | * |
| * Engine intake air system. | * |
| * Exhaust system blocked. | * |
| * Engine management system. | * |
| * Fault in ignition system (petrol engines only). | * |
| * Turbocharger (only diesel engine). | * |
| * Incorrect valve timing, timing chain, timing belt or timing sprocket damaged. | * |
| Noisy running | * Engine auxiliary components loose or damaged. | * |
| Noisy running, misfiring or backfiring | * Incorrect fuel | * Determine which type of fuel was the last put in the tank (note the country specific fuel specifications). |
| * Water in fuel or fuel contaminated. | * Check the fuel system for water or other contamination. |
| * Valve timing incorrect, timing chain, timing belt or timing sprocket damaged. | * |
| Noisy running or valve train noise | * Valve clearance too large due to faulty hydraulic valve tappets. | * |
| * Timing chain or timing belt damaged. | * |
| * Timing chain or timing belt incorrectly tensioned. | * |
| * Timing chain guides worn of damaged (only petrol engines). | * |
| Noisy running or engine block | * Engine components - Pistons - Piston rings - Connecting rod large end, main bearing or thrust bearing journals - Connecting rods bent or damaged. | * |
