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CYLINDER COMBUSTION PRESSURE LEAKAGE The combustion pressure leakage test provides an accurate means for determining engine condition. Combustion pressure leakage testing will detect: ing). • Leaks between adjacent cylinders or into water jacket. • Any causes for combustion/compression pressure loss. (1) Check the coolant level and fill as required. DO NOT install the radiator cap. (2) Start and operate the engine until it attains normal operating temperature, then turn the engine (3) Remove the spark plugs. (5) Remove the air cleaner. turer’s instructions. The shop air source for testing (7) Perform the test procedures on each cylinder according to the tester manufacturer’s instructions. All gauge pressure indications should be equal, with no more than 25% leakage. FOR EXAMPLE: At 552 kPa (80 psi) input pres- sure, a minimum of 414 kPa (60 psi) should be main- Refer to the Cylinder Combustion Pressure Leak- age Test Diagnosis chart. CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART CONDITION POSSIBLE CAUSE CORRECTION AIR ESCAPES THROUGH Intake valve bent, burnt, or not Inspect valve and valve seat. AIR ESCAPES THROUGH Exhaust valve bent, burnt, or not Inspect valve and valve seat. AIR ESCAPES THROUGH Head gasket leaking or cracked Remove cylinder head and inspect. MORE THAN 50% LEAKAGE Head gasket leaking or crack in Remove cylinder head and inspect. MORE THAN 25% LEAKAGE AND Stuck or broken piston rings; Inspect for broken rings or piston. ENGINE OIL LEAK INSPECTION Begin with a thorough visual inspection of the engine, particularly at the area of the suspected leak. (1) Do not clean or degrease the engine at this time because some solvents may cause rubber to (2) Add an oil soluble dye (use as recommended by manufacturer). Start the engine and let idle for (3) Using a black light, inspect the entire engine for fluorescent dye, particularly at the suspected area (4) If dye is not observed, drive the vehicle at var- ious speeds for approximately 24km (15 miles), and (4) If the oil leak source is not positively identified at this time, proceed with the air leak Air Leak Detection Test Method (1) Disconnect the breather cap to air cleaner hose at the breather cap end. Cap or plug breather cap (2) Remove the PCV valve from the cylinder head cover. Cap or plug the PCV valve grommet. (3) Attach an air hose with pressure gauge and regulator to the dipstick tube. CAUTION: Do not subject the engine assembly to 9 - 14 4.0L ENGINE WJ DIAGNOSIS AND TESTING (Continued) |