14 4 DLT ENGINE gasket. To ascertain the point of leakage, spray small quantity of clean engine oil in to cylinder showing low pressure. If it improves, wear in piston rings / cylinder bore is indicated. If it does not, leakage past the valves is indicated. If compression pressure of adjacent cylinder is also on lower side and equal, it may be due to blown cylinder head gasket. 2. EXCESSIVE ENGINE OIL CONSUMPTION High engine oil consumption may also lead to overhauling of the engine but before proceeding to overhauling, check following points : 1. Make sure that there is absolutely zero external leakage of the oil (i. e. from the camshaft oil seal, crankshaft oilseal, oil sump gasket, oil pump gasket, cylinder head cover gasket etc. 2. Ensure that oil separator condition is OK & no leakage in the circuit. 3. If no external leakage is found, determine the exact engine oil consumption, as per following procedure. Determining exact engine oil consumption : Caution : Do not make a rough estimate of engine oil consumption by noting the kilometers covered by the vehicle at any random stage and finding oil consumed from the topped up position taking into consideration dipstick level and oil tank capacity. Procedure : 1. Once it is doubted that engine oil consumption is higher, place the vehicle on level ground. 2. Top up oil sump to its capacity as recommended. 3. Warm up the engine so that oil temperature is 75-800 C. 4. Now take a clean vessel, place it below the drain plug of oil tank. 5. Drain the hot oil into the clean vessel. Drain it fully. 6. Screw in oil sump drain plug and tighten it. 7. Weigh the vessel along with oil let this weight be ‘w1’ gms. 8. Refill the weighed oil into the oil tank. Do not spill any oil. The vessel used for draining should not be used for any other purposes. 9. Load the vehicle approximately to rated GVW. Drive vehicle for at least 200 km/120 miles under normal operating conditions. Let this drive distance be ‘D’ kms. 10. Immediately after the test drive, place the vehicle at the same spot from where it started. 11. Now place the same previously used vessel below the oil tank, unscrew the drain plug and drain off oil into the vessel drain the tank fully. 12. Weigh the vessel along with oil, now for the second time. Let this weight be ‘W2’ gms. 13. Find out standard oil consumption as : Standard oil consumption = (W1-W2) (Wt. of oil consumed gms.)X1000 C (Litres / 1000km) sp. gvt. of oil (gm)XD (drive dist. in km.) C = (W1-W2) litres/1000km 0.88 x D If the oil consumption value is more than 0.8 Ltr./ 1000 kms then engine needs further investigation. Note : The oil consumption of engine depends on the oil conditions (e. g. viscosity, cleanliness and grade of oil etc.) and the driving conditions. If the vehicle is driven in high speeds, as may be the case on highways, and /or with frequent accelerations and decelerations for comparatively long time, then the oil consumption may show variation over the specified values. 3. EXTREMELY LOW OIL PRESSURE Check the following : a. External leakages. b. Oil level in sump upto maximum mark on dipstick. c. Oil pressure indicator for proper functioning. d. Functioning of pressure relief valve on oil pump. e. Oil pump performance. f. Clogged oil filter If oil pressure is found to be less than 2.8 bar at maximum speed and 1.2 bar at idling speed, it may be due to improper functioning of oil pump or defect in oil pump relief valve. If low oil pressure is not on account of above factors, wear of journals / bearings is indicated for which overhaul of engine may be considered. 4. MECHANICAL FAILURES Defective water pump or alternator can be a source of mechanical noise. Defect can be located by replacing alternator, water pump with NEW one. Metallic knocking sound from an engine may be due to faulty injection, excessive clearance in main and big end bearings, small end bush, tappets, piston slap, seizing of piston rings, scored cylinder bore or breakage of any moving parts. Noise due to defective fuel injection equipment is generally termed as ‘DIESEL KNOCK’ and can be eliminated by attending to fuel injection equipment. By cutting off high pressure line to individual injectors with engine running will pin point the cylinder with Diesel Knock. Overhauling of fuel system will set right Diesel Knock. Dismantling of engine may be considered if still noise occur even after attending all above mentioned problems. Noise can be from turbocharger unit. For details refer the trouble shooting chart in turbocharger section.
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