FAILURE ANALYSIS
78
A properly maintained engine will provide years of ser-
vice. Occasionally an engine will fail. An important part
of working on engines is finding out why they failed.
Was it something the customer did? Was it a manufac-
turing defect? Did the engine just wear out? All of these
questions need to be answered when a failed engine is
found.
Engines can fail in a variety of ways but most failures
can be classified in the following categories:
• Abrasive ingestion
• Insufficient lubrication
• Over heating
• Over speed
• Mechanical breakage/ wear
NOTE: There may be a combination of failures.
Finding the cause of an engine failure requires the
complete disassembly of an engine and careful exami-
nation of the parts.
With a good understanding of how the engine works,
close examination of the parts and experience, an
understanding of why the engine failed can be
reached.
Abrasive Ingestion
Abrasive Ingestion is when hard particles are intro-
duced into the engine. Particles can be introduced into
the engine by leaks in the air intake system, through a
dirty oil fill plug or by particles of metal that wore off of a
part, especially during the break in cycle. Particles may
also be introduced through worn or improperly installed
seals or gaskets.
1. Abrasive particles that enter the engine through
the intake system can be sand or dirt.
See Figure 11.1.
2. An abrasive particle can enter the engine by
bypassing an improperly installed air filter or
through leaks in the intake system. Usually there
will be tracking marks were the particles enter
the system. Use these marks to find the source
of the abrasives.
NOTE: Dirt can also work its way through a
poorly maintained air filter.
See Figure 11.2.
Figure 11.1
Figure 11.2
CHAPTER 11: FAILURE ANALYSIS
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