Note. 3.0L engines are equipped with hydraulic tappets and do not require regular adjustment of valve clearances. On 4.2L models, valve adjustment should be made in accordance with the vehicle's routine maintenance schedule.
1. Start the engine and warm it up to normal operating temperature.
Note. If the valves are adjusted after the cylinder head or rocker arms have been serviced, the initial setting should be made with a cold engine.
2. Remove the air intake hose between the air cleaner and the pre-cyclone dust separator. To prevent dirt from entering the engine, wipe the joint between the cylinder head cover and the head housing with a suitable solvent.
3. Disconnect the engine ventilation hoses, give the fixing bolts and remove the cylinder head cover.
4. Turning the engine in the normal direction (see Section general information at the beginning of the chapter), bring the piston of the first cylinder to the TDC position of the end of the compression stroke. In this case, the distribution mark on the crankshaft pulley must be aligned with the zero mark on the cover of the timing gear drive (see accompanying illustration), and two valves of the sixth cylinder - to take up the overlapping positions: one immediately preceding the closing, the second - opening.
5. Using a 0.38 mm feeler blade, estimate the gap between the end of the inlet valve stem of the first cylinder and the working surface of its rocker (see accompanying illustration). The blade should pass through the gap with slight resistance.
6. If adjustment is necessary, loosen the rocker arm adjusting screw locknut and turn the screw until the desired result is achieved. After fixing the screw in the selected position, tighten the locknut. Check the gap again with a feeler gauge after tightening the locknut.
7. Proceeding in a similar way, check and correct the gaps of the following valves: exhaust valves of the first, third and fifth cylinders, intake of the second and fourth cylinders.
8. Turn the crankshaft one full turn in the direction of normal rotation so that the sixth cylinder piston moves to the TDC position of the end of the compression stroke. The above overlap position will be occupied respectively by the valves of the first cylinder.
9. Now check and adjust the clearances of the exhaust valves of the second, fourth and sixth cylinders and the intake valves of the third, fifth and sixth.
10. Reinstall the cylinder head cover, replacing the gasket if necessary, and the air intake sleeve.
11. Start the engine and check the cylinder head cover for signs of leaks. If any are found, remove the cause.