Engine Valve Lash - Inspect/Adjust
Required Tools
| Tool | Part Number | Part Description | Qty |
|---|---|---|---|
| A | 385-4005 | Angled Feeler gauge | 1 |
Illustration 1: Cylinder and valve location
(A) Exhaust valve
(B) Inlet valve
Causes of Valve Wear and Lash Issues
If the valve lash requires adjustment multiple times in a short period, it indicates excessive wear in another part of the engine. Identify and repair the underlying problem to prevent further engine damage.
Insufficient valve lash can lead to rapid wear of the camshaft and valve lifters, and may indicate worn valve seats.
Valves can become worn due to:
- Incorrectly operating fuel injection nozzles
- Excessive dirt and oil in the air filters
- The engine's load capacity being frequently exceeded
Excessive valve lash can cause broken valve stems, springs, and spring retainers, leading to emissions exceeding specifications.
Excessive valve lash can indicate:
- Worn camshaft and valve lifters
- Worn rocker arms
- Bent pushrods
- Broken socket on the upper end of a pushrod
- Loose adjustment screw for the valve lash
If the camshaft and valve lifters show rapid wear, investigate fuel contamination or dirty lubrication oil as potential causes.
Valve Lash Check
An adjustment is not necessary if the valve lash measurement is within the acceptable range. Check the valve lash with the engine stopped. Engine temperature does not affect the valve lash setting.
If the measurement is outside the acceptable clearance, an adjustment is necessary. Refer to "Valve Lash Adjustment" for the procedure.
Valve Lash Adjustment
NOTICE: It is crucial to follow this valve lash adjustment procedure precisely. Do not use traditional opposing cylinders methods. Failure to adhere to the correct procedure may result in severe engine damage.
The procedure to adjust the engine valve lash for the C4.4 engine differs from conventional engines due to altered valve opening and closing events.
| Valve Lash Specification | |
|---|---|
| Exhaust Valves | Inlet Valves |
| 0.35 ± 0.05 mm (0.0138 ± 0.0020 inch) | 0.35 ± 0.05 mm (0.0138 ± 0.0020 inch) |
Firing Order: 1-3-4-2
(2) The No. 1 Cylinder is at the front of the engine.
Note for New Engines: Check and reset valve lash after the first 500 hours and again after the next 500 hours. Subsequent checks should be at 1000-hour service intervals.
Note for Remanufactured Engines: If pushrods are replaced with new parts, adjust the valve lash to 0.25 ± 0.05 mm (0.0098 ± 0.0020 inch) for the initial rebuild. Reset tappets to 0.35 ± 0.05 mm (0.0138 ± 0.0020 inch) at normal service intervals thereafter.
Illustration 2: Setting the valve lash
(A) Angled feeler gauge
(1) Adjustment screw
(2) Locking screw
WARNING: Accidental engine starting can cause injury or death. To prevent this, turn the ignition switch to OFF and place a "Do Not Operate" tag at the ignition switch location.
Illustration 3
Procedure:
- Remove the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove and Install" for the removal procedure.
- Note: When removing or installing the valve mechanism cover, check the electrical harness. Ensure the injector harness is not trapped and does not contact the cover. Replace the harness if damaged.
- Rotate the crankshaft clockwise until the piston of No. 1 cylinder is at the top center position on the compression stroke. The exhaust valves and inlet valves of No. 4 cylinder will be in valve overlap. Measure the valve lash on the exhaust valves (1) and inlet valves (2) of No. 1 cylinder. Adjust to the settings in Table 2 if necessary.
- a. Loosen the valve adjustment locknut on the adjustment screw (1).
- b. Place Tooling (A) between the rocker arm and the valve. Turn the adjustment screw (1) while preventing the locknut (2) from turning. Adjust valve lash to the correct specification.
- c. After each adjustment, tighten the valve adjustment screw locknut to 21.5 to 32.5 N·m (15.9 to 24 lb ft) while holding the adjustment screw (1) in position.
- Rotate the crankshaft 180 degrees in the direction of engine rotation until the piston of No. 3 cylinder is at the top center position on the compression stroke. The exhaust valves and inlet valves of No. 2 cylinder will be in valve overlap. Adjust the valve lash for the inlet valves (5) and exhaust valves (6) of No. 3 cylinder.
- Complete the sequence of checks according to Table 3 for all cylinders. Reinstall the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove and Install" for the installation procedure.
