No valve lash adjustment is necessary or possible on any of the gasoline engines covered in this guide. Hydraulic valve lifters automatically maintain zero clearance. After engine reassembly, these lifters adjust themselves as soon as engine oil pressure builds up.Diesel Engine (1997-98)
Valve adjustment is required on the 12-valve diesel engine every 24,000 miles (38,000 km).
- The engine must be cold for this adjustment (below 140ºF or 60ºC).
- Disconnect the negative battery cable.
- Remove the valve cover.
- Manually turn the engine and use the timing pin to locate Top Dead Center (TDC) for cylinder No. 1. Disengage the timing pin after locating TDC.
Perform the following two-step procedure to adjust the valves. Refer to the accompanying illustrations to determine which valves to adjust in each of the steps:
- Valve lash is measured between the rocker arm and the end of the valve. Check the lash by inserting a feeler gauge between the rocker arm and the valve. Adjust the clearance, if necessary. The clearance for the intake valves is 0.010 in. (0.254mm). The clearance for the exhaust valves is 0.20 in. (0.508mm). Adjust the lash by loosening the locknut on the rocker arm and turning the adjusting screw. After the adjustment is made, tighten the locknut to 18 ft. lbs. (24 Nm) and recheck the lash to be sure it did not change as the locknut was being tightened.
- Double-check that the timing pin is disengaged, then mark the pulley and turn the engine crankshaft 360º in the normal direction of rotation (clockwise). Check and adjust the clearance of the indicated valves following the same specifications as in Step 4a.
- Install the rocker cover with a new gasket, and then attach the fuel line to the injector. Start the engine and check for leaks.
Valve adjustment is not a routine maintenance item. Measurements should be taken while troubleshooting an operating problem or after valve train components have been removed/replaced.
- Measurements must be taken on a COLD engine with the coolant temperature below 140ºF (60ºC).
- Refer to the accompanying illustration. Rotate the crankshaft to align the timing marks as shown and measure clearance with a feeler gauge between rocker arm socket and crosshead at the appropriate valves as shown in the illustration.
- If clearance is not within specification, loosen the locknut and turn the adjusting screw as required to achieve the proper clearance. Tighten the locknut and recheck.