21. Corrective Action for Valve Sticking
NOTICE: If valve sticking is a problem, complete the 1000-hour Engine Inspection Checklist in
Chapter 05-20 (regardless of the number of engine operating hours) (Figure 15). After
correcting the cause of valve sticking, complete the 1000-hour inspection after the next
1000 hours of engine operation, unless valve sticking occurs again.
Sticking between the valve stem and guide (on intake and exhaust valves) can
substantially change valve opening and closing. If the valve cannot open or close
correctly, incomplete combustion will occur, which can cause formation of more
deposits and increased valve sticking. Because a correctly-timed sequence of valve
opening and closing is essential to efficient and reliable engine operation, the cause of
valve sticking must be identified and corrected.
WARNING
A STUCK VALVE CAN CAUSE ENGINE FAILURE.
NOTICE: If one valve is sticking, examine all other valves on all of the engine cylinders as a
precaution.
A. Per Chapter 12-10 complete an oil and filter change and have an analysis done on the
metallic solids in the oil filter to identify the contamination and find the source to correct the
problem. Refer to the latest revision of Service Bulletin No. SB-480 for any additional
details.
B. If the source of the oil contamination cannot be found or corrected, complete the following
procedures in Chapter 12-10:
(1) Replace the oil filter (more often) after every 25 hours of operation (instead of after every
50 hours of engine operation.)
(2) Complete an oil change after every 25 hours of operation (instead of after every 50 hours
of engine operation.)
C. Complete an air filter change at more frequent intervals.
D. Examine the cooling air baffles and baffle strips for contamination. Remove any
contamination.
E. Identify with a tag and remove the top spark plugs from the engine cylinders per the “Spark
Plug Removal” procedure in Chapter 74-20.
F. Identify the location of each cylinder and valve train component for reference on assembly
and remove the cylinder and valve train components per the “Cylinder Removal” section in
this chapter.
G. Remove the intake and exhaust valves per the “Intake Valve Removal” and “Exhaust Valve
Removal” sections in this chapter.
H. Examine the valve stem keys/caps (Figure 15) for wear. Look for any distinct, uniform
patterns. Replace worn valve stem keys or caps.
NOTICE: Refer to the latest revision of the Service Table of Limits - SSP-1776 for valve
guide dimensions to use the correct reamer.
Use reamer tools to remove hardened carbon from the valve guides.
I. Apply ordinary cup grease on the flutes of the reamer to remove the deposits on the reamer.
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