LO 9-8 Outline maintenance procedures and practices used to service diesel engine cylinder heads

1. Maintenance of Cylinder Heads and Valve Trains

Maintenance of Cylinder Heads and Valve Trains

Maintenance of cylinder heads is often required when coolant or combustion leaks occur. In addition, valve seats and faces can become worn or damaged, which requires replacement during a cylinder head overhaul and service Figure 60. Continual pounding of the valve faces and seats can take place whenever valves are out of adjustment; this prevents effective performance of the quieting ramps on the camshaft, which slows down valve velocity as they seat. Valve faces become recessed when worn out. Excessive oil consumption and extended idle time can contribute to valve seat and face pitting, which eventually results in valve leakage Figure 61. Very long periods of extended idle can lead to excessive formation of slobber on the back of the valve Figure 62. If the slobber solidifies during a cold shutdown period while the valve is open, the valve and piston will make contact and the valve will bend.

FIGURE 09-60: Worn or damaged valves should be replaced during a cylinder head overhaul and service.

FIGURE 09-61: The intake and exhaust valve faces have worn away with accumulated distance. Most valves recede into the valve face and seat, which causes valve lash to disappear.

FIGURE 09-62: An exhaust valve slobbered from excessive engine idle.