Perkins 4008-30 Operation And Maintenance Manual page 90

90
Maintenance Section
Overhaul (Top End)
Note: It is possible for oil analysis to 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.
Perkins recommends that at 7500 hours for prime
power and base load applications or 5 years for
standby applications, the following components
should be removed from the engine:
• Piston assembly
• Piston rings
• Cylinder liner
• Connecting rod bearings
Note: One cylinder should be selected to have the
components removed.
Contact your Perkins distributor or Perkins dealer for
more information. An inspection of the components
by the Perkins distributor or Perkins dealer can help
to determine when a major overhaul is required as
well as the other factors.
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
Replace the crankshaft vibration dampers.
Overhaul (Top End)
Scheduling a Top End Overhaul
Top end overhauls should be scheduled depending
on valve recession. Record the valve depth at each
service and then calculate the valve recession. This
measurement provides an accurate indication of the
rate of valve wear. This measurement can be used to
predict when a cylinder head must be replaced.
Note: Generally, cylinder heads wear out at different
rates. Sometimes, servicing the cylinder heads at
different times may be the most economic decision.
The decision depends on the valve recession of the
individual cylinders. However, this decision must
include the costs of extra 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.
Contact your Perkins distributor or Perkins dealer for
more information.
Monitoring Valve Seat Wear
At the required service interval, record 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).
Note: After the engine valve lash is recorded,
Perkins recommends that the valve depth is
measured and recorded.
SEBU9077-02
i08253506