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Top End Overhaul Information
A top end overhaul involves servicing the cylinder heads and turbochargers. Also, some other engine components are inspected.Top end overhauls require more tools than preventive maintenance. The following tools are needed for restoring the engine to factory specifications:
Torque wrenches
Dial indicators
Accurate measurement tools
Cleaning equipment
Rebuilding equipmentCat dealers are equipped with these tools. Caterpillar dealers can provide a flat rate price for a top end overhaul.Unexpected problems may be found during a top end overhaul. Plan to correct these problems, if necessary.
Build up in the cylinders from excessive oil consumption
Build up in the cylinders from contamination of the fuel
Plugging of the aftercooler from coolant that is poorly maintained
Plugging of the aftercooler from contamination of the inlet air
Degradation of the oil cooler from hydrogen sulfide in the fuelInspect the following components according to the instructions that are in Cat reusability publications. Refer to Guidelines for Reusable Parts and Salvage Operations, SEBF8029, "Index of Publications on Reusability or Salvage of Used Parts".Your Cat dealer can provide these services and components. Your Cat dealer can ensure that the components are operating within the appropriate specifications.If you elect to perform an overhaul without the services of a Cat dealer, be aware of the following recommendations.Replacing of Components
Note: The cylinder head may be rebuilt, when possible.Replace the following components during a top end overhaul.
Alternator and fan drive belts
Cylinder heads and gaskets
Hoses and clamps
Rod ends for the control linkage of the actuator
Spark plugs
Spark plug wires
Water temperature regulatorRebuilding of Components
Rebuild the following components during a top end overhaul:
Gas regulator
Starting motor
Turbocharger
Water pumpsNote: Periodic inspection of the turbocharger is recommended for determining when the turbocharger will require an overhaul. In a few applications, the turbocharger may require rebuilding prior to the top end overhaul. An example is an application with loads that vary frequently. In these cases, rebuilding the turbocharger normally occurs separately from rebuilding the cylinder heads. Some applications can operate longer before the turbocharger requires rebuilding. Only experience can determine the actual need.Inspecting of Components
Clean the following components. Pressure-test the components. Replace the components, if necessary:
Aftercooler core (if equipped)
Oil cooler coreNote: If proper maintenance of the cooling system is not performed, the aftercooler core can be difficult to clean.Note: This procedure may be used for cleaning both the aftercooler core and the oil cooler core.
Remove the core. For the procedure, see the Service Manual, "Disassembly and Assembly" module.
Turn the core upside-down to remove debris.
Do not use a high concentration of caustic cleaner to clean the core. A high concentration of caustic cleaner can attack the internal metals of the core and cause leakage. Only use the recommended concentration of cleaner.
Do not use a high pressure spray for cleaning the fins of the core. A high pressure spray can damage the surface of the fins and reduce the flow of air through the core.
Back flush the core with cleaner.Caterpillar recommends the use of Hydrosolv liquid cleaner. Use a 2 to 5 percent concentration of the cleaner at temperatures up to 93 °C (200 °F). Refer to Application Guide, NEHS0526 or consult your Cat dealer for more information.
Steam-clean the core to remove any residue. Flush the fins of the core. Remove any other trapped debris.
Wash the core with hot, soapy water. Rinse the core thoroughly with clean water.
Personal injury can result from air pressure.Personal injury can result without following proper procedure. When using pressure air, wear a protective face shield and protective clothing.Maximum air pressure at the nozzle must be less than 205 kPa (30 psi) for cleaning purposes.
Dry the core with compressed air. Direct the air in the reverse direction of the normal flow.Note: The test pressure for the oil cooler is 790 kPa (115 psi). The maximum differential pressure of water for the aftercooler is 44 kPa (6 psi). The maximum differential pressure of air for the aftercooler is 5.1 kPa (.74 psi).
Inspect the core to ensure cleanliness. Pressure-test the core. Many shops that service radiators are equipped to perform pressure tests. If necessary, repair the core.
Install the core. For the procedure, see the Service Manual, "Disassembly and Assembly" module.For more information on cleaning the cores, consult your Cat dealer.Exhaust Bypass
Inspect the condition of the exhaust bypass (if equipped). Recondition the component, if necessary. See this Operation and Maintenance Manual, "Exhaust Bypass - Inspect" topic (Maintenance Section).Governor
Inspect the governor for proper operation. Make any repairs that are necessary.Transformers
The transformers produce a voltage increase. For good operation, the connections must be clean and secure. Inspect the transformers for the following conditions:
Dirty insulator
Loose connections
Loose connector
MoistureTest the resistance of the transformers according to the Service Manual, "Specifications" module. Consult your Cat dealer for assistance.