B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 003-004   Overhead Set

Diagnosing component malfunctions – rocker lever, valve stem, push tube, tappet, and camshaft.

The rocker lever group consists of the rocker lever assemblies, rocker assembly oil manifold, valve cover, and crankcase breather.

Each cylinder of the engine has a separate rocker lever assembly. The pedestal support has drillings to route the oil flow to the shaft and levers.

The rocker levers are push tube actuated and use an adjusting screw to control the clearance between the rocker lever and valve stem. The rocker levers do not use a bushing in the bore for the rocker lever shaft. The rocker lever must be replaced if the bore is damaged or worn beyond the specification limit.

The ball end of the push tube fits into the ball socket in the tappet. The other end of the push rod has a ball socket in which the ball end of the rocker lever adjusting screw operates.

NOTE: The phosphorous and zinc levels in MidRange natural gas engine oils help in the lubricating of sliding tappets.

Excessive valve lash can indicate a worn valve stem, push tube, valve tappet, or rocker lever.

Loose rocker levers and the need to reset the valve clearance frequently can also indicate camshaft lobe or tappet wear. If an inspection of the rocker levers, valve stems, and push tubes does not show wear, then tappet and/or camshaft lobe wear can be suspected. Refer to Procedure 001-008 and Refer to Procedure 004-015.

CAUTION  Anytime a new camshaft is installed, new tappets and push tubes must also be installed. Failure to do so can cause severe engine damage.

The camshaft lobes can be inspected after removing the lubricating oil pan.

The tappets can also be inspected with the lubricating oil pan removed. Remove the push tubes, lift the tappets, and inspect the tappet faces.

A severely damaged camshaft journal(s) can generate metal chips that will be found in the lubricating oil pan and oil filter.

NOTE: As the clearance between the camshaft bushing(s) and camshaft journal(s) increases, oil pressure and volume will decrease, causing damage to the camshaft and tappets.

NOTE: All valve adjustments must be made when the engine is cold, and stabilized coolant temperatures are at 60°C [140°F] or below.

Remove the rocker lever cover capscrews, insulators, and spacers from the cover.

Remove the rocker lever covers.

Engine Barring Tool, Part Number 3824591

Locate top dead center for cylinder Number 1.

Use a 1/2-inch drive, Engine Barring Tool, Part Number 3824591 to rotate the engine (clockwise when facing the damper) until cylinder Number 4 (for 4 cylinder) or cylinder Number 6 (for 6 cylinder) intake rocker arm starts to open the intake valve.

Wiggle the rocker arm while barring the engine; when the rocker arm gets tight, stop barring.

NOTE: On the liquefied petroleum gas application, the evaporator must be removed in order to use the engine barring tool.

Refer to Procedure 005-094 in Section 5.

Feeler Gauge

NOTE: The clearance is correct when some resistance is “felt” when the feeler gauge is slipped between the valve stem and the rocker lever.

Engine Valve Adjustment

Locate top dead center for cylinder number 1.

Set only the valves indicated by the arrows in the illustration (E = exhaust, I = intake).

Holding the locknut steady with the wrench, adjust the valve clearance with the screwdriver or Allen wrench.

Tighten the locknut and measure the valve lash again.

Mark the pulley, and rotate the crankshaft 360 degrees.

Adjust the valves as indicated in the illustration.

Set only the valves indicated by the arrows in the illustration (E = exhaust, I = intake). Do not set valves that are not indicated.

Install the rocker lever covers, and tighten the capscrews.

Refer to Procedure 003-011.