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.
i06546607
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
Every 500 service hours record the valve lash. 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
Table 19
Recorded clearances on
A1 cylinder
Total valve wear
Hours
Inlet
Exhaust
Inlet
Exhaust
500
0.4mm
0.4mm
0
0
1000
0.4
0.4
0
0
1500
0.35
0.35
0.05
0.05
2000
0.35
0.35
0.1
0.1
2500
0.3
0.3
0.2
0.2
3000
0.25
0.3
0.35
0.3
3500
0.25
0.35
0.5
0.35
4000
0.25
0.3
0.65
0.45
After 4000 hours running, the valve seat wear on the
inlet is 0.65 mm (0.026 inch) and the exhaust is
0.45 mm (0.018 inch).
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SEBU9077-01
