Other factors must also be considered for
determining a major overhaul:
• The service hours of the engine
• The wear metal analysis of the lube oil
• An increase in the levels of noise and vibration
An increase of wear metals in the lube oil indicates
that the bearings and the surfaces that wear may
need to be serviced. An increase in the levels of
noise and vibration indicates that rotating parts
require service.
Note:
Oil analysis can indicate a decrease of wear
metals in the lube oil. The cylinder liners may be
worn so that polishing of the bore occurs. Also, the
increased use of lube oil will dilute the wear metals.
Monitor the engine as the engine accumulates
service hours. Consult Perkins Engines Stafford
about scheduling a major overhaul.
Note:
The driven equipment may also require service
when the engine is overhauled. Refer to the literature
that is provided by the OEM of the driven equipment.
Major Overhaul Information
During a major overhaul, all the bearings, seals,
joints, and components that wear should be
disassembled. The parts should be cleaned. The
parts should then be inspected. If necessary, the
parts should be replaced. The crankshaft should be
inspected and measured for wear. The crankshaft
may require regrinding. Alternatively, the crankshaft
may be replaced.
Inspecting Components
Inspect the following components during a major
overhaul.
• Radiator and system
• Camshaft
• Camshaft followers
• Connecting rods and bearings
• Crankshaft and bearings
• Gear train
• Inlet air piping
• Oil cooler
• Pistons and rings
• Cylinder liners
• Cylinder heads
• Inlet and exhaust valves
Replace the crankshaft vibration dampers.
i08304220
Overhaul
(Top
End)
Scheduling
a
Top
End
Overhaul
Top
end
overhauls
should
be
scheduled
according
to
the
recession
of
the
valve
stems.
This
measurement
provides
an
accurate
indication
of
the
rate
of
valve
wear.
This
measurement
can
be
used
to
predict
when
a
cylinder
head
requires
replacement.
Note:
Generally,
cylinder
heads
wear
out
at
different
rates.
Sometimes,
servicing
the
cylinder
heads
at
different
times
may
be
the
most
economic
decision.
This
action
depends
on
the
valve
stem
projection
of
the
individual
cylinders.
However,
this
decision
must
include
the
costs
of
additional
downtime
that
is
caused
by
this
procedure.
Perform
an
economic
analysis
to
determine
if
cylinder
heads
should
be
serviced
as
a
group
or
divided
into
smaller
groups.
Top
End
Overhaul
Information
A
top
end
overhaul
involves
servicing
the
cylinder
heads.
During
a
top
end
overhaul,
one
piston
should
be
removed.
Inspect
the
piston,
piston
rings,
and
the
cylinder
liner.
The
condition
of
these
components
will
determine
the
period
of
the
major
overhaul.
Refer
to
Service
Manual
for
more
information.
Monitoring
Valve
Seat
Wear
Record
the
engine
valve
lash,
for
more
information
refer
to
the
Operation
and
Maintenance
Manual,
“Maintenance
Interval
Schedule”.
The
monitoring
of
the
valve
seat
wear
should
be
carried
out
before
any
adjustment
of
the
valve
lash.
1.
Remove the rocker covers.
2.
Refer to Systems Operation, Testing and
Adjusting, “Valve Lash - Adjust”.
3.
On all engine cylinders, record the clearance
before any adjustments are made.
4.
Set the valve bridges.
5.
Adjust the valve lash to 0.4 mm (0.016 inch).
The recorded values can be used to identify any
excessive valve seat wear on individual valves. The
recorded values can be used to schedule a top end
overhaul.
An example of recorded valve lash
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