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303-00-6 Engine System — General Information 303-00-6 DIAGNOSIS AND TESTING (Continued) 7. Install the components in reverse order, observing Components Tests the specified tightening torques. Engine Oil Leaks 8. Reset the PCM fault memory. NOTE: Before installing new gaskets or oil seals, Interpretation of the Results make sure that the fault is clearly established. If the oil leak cannot be identified clearly by a visual The indicated compression pressures are considered inspection, carry out a pressurized crankcase leak within specification if the lowest reading cylinder is check: within 75% of the highest reading. Pressurised leak check CAUTION: If engine oil is sprayed into the combustion chamber, after carrying out the 1. Clean the engine with a suitable cleaning fluid to measurement run the engine at 2000 rpm for remove all traces of oil. about 15 minutes, in order to burn the oil and 2. Block off the line to the PCV valve. prevent damage to the catalytic converter. 3. Apply a regulated air supply line to the fresh air If the measurement on one or more cylinders is much makeup point on the rocker cover. lower than the specified value, spray some engine oil 4. Pressurise the crankcase to 35 kPa. into the combustion chamber and repeat the 5. Check for air leaks by washing the suspect area compression measurement. with a solution of soapy water and watching for If the reading greatly improves, the piston rings are bubbles. damaged. 6. Repair all leaks as necessary. If the reading stays the same, the cause is either damaged valve seats or valve stem seals. Compression Test If the measurements for two cylinders next to each General Remarks other are both too low then it is very likely that the cylinder head gasket between them is burnt through. NOTE: Removing fuses and disconnecting electrical This can also be recognized by traces of engine oil in components causes the powertrain control module the coolant and/or coolant in the engine oil. (PCM) to log an error message. After the measurements have been carried out this error Excessive Engine Oil Consumption message should be cleared from memory by The amount of oil an engine uses will vary with the connecting to PDU. way the vehicle is driven in addition to normal The compression pressure should be checked with engine-to-engine variation. This is especially true the engine at operating temperature. during the first 15,000 km when a new engine is being broken in or until certain internal components become Check The Compression Pressure conditioned. Vehicles used in heavy-duty operation may use more oil. The following are examples of WARNING: On manual transmissions, shift heavy-duty operation: the transmission into neutral. On automatic trailer towing applications transmission vehicles, select ’’P’’. Failure to severe loading applications follow these instructions may result in personal sustained high speed operation injury. Engines need oil to lubricate the following internal 1. Remove the fuel pump relay. components: 2. Start the engine - the engine will start, run for a cylinder block cylinder walls few seconds then stall. pistons and piston rings 3. Remove the spark plugs. intake and exhaust valve stems 4. Install the compression tester. intake and exhaust valve guides 5. Install an auxiliary starter switch in the starting circuit. With the ignition switch OFF, using the all internal engine components auxiliary starter switch, crank the engine a When the pistons move downward, a thin film of oil is minimum of five compression strokes and record left on the cylinder walls. As the vehicle is operated, the highest reading. some oil is also drawn into the combustion chambers NOTE: The approximate number of compression past the intake and exhaust valve stem seals and strokes required to obtain the highest reading. burned. 6. Repeat the test on each cylinder, cranking the The following is a partial list of conditions that can engine approximately the same number of affect oil consumption rates: compression strokes. engine size G37831 en |