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Weichai America Corp.
Revision: August 2019 43
Clean the cylinder head, focusing on the combustion chamber surface, valve seat, intake and
exhaust valves, and intake and exhaust passages. Remove the carbon deposits and mucilage
glue, and check the surface condition.
1.
Appearance Inspection:
Check the cylinder cover for any discoloration or cracks. If any cracks are discovered, a leak
test should be done.
2.
Valve Recession:
Valve recession is the vertical distance between valve undersurface and cylinder cover
undersurface. Any difference between the measured and required values of valve recession
can reflect the degree of wear on the valve and valve seat. A depth micrometer can be used to
measure valve recession, as shown in Figure 9-7 below:
Fig. 9-7 A Depth Micrometer
Reference Table 9-1 for valve recession requirements. If valve recession exceeds the allowed
range, the cylinder cover must be replaced to ensure engine reliability. If valve recession
doesn’t exceed allowed range, disassemble the valve and check the sealing surface between
the valve and valve seat for wear and abnormal damage.
Table 9-1 Valve Recession Specifications
Required value of valve recession (mm)
Intake valve
1.00~1.45
Exhaust valve
1.00~1.45
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