A major overhaul includes the work that is done for a top end overhaul. All other parts that are visible during the major overhaul are completely inspected. The seals and gaskets that are exposed are also replaced. The internal passages of the engine are cleaned.
Your Caterpillar dealer can provide these services and components. Your Caterpillar dealer can ensure that the components are operating within the appropriate specifications.
If you elect to perform an overhaul without the services of a Caterpillar dealer, be aware of the following recommendations.
Replace the following components during the major overhaul. In addition, replace the components that are specified in this Operation and Maintenance Manual, "Overhaul (Top End)" topic.
- Connecting rod bearings
- Crankshaft seals
- Exhaust shields
- Gaskets and seals
- Main bearings
- Piston rings
- Valve rotators
Components for Inspection, Rebuilding or Exchanging
Inspect the following components according to the instructions that are in Caterpillar reusability publications. Refer to Guidelines for Reusable Parts and Salvage Operations, SEBF8029, "Index of Publications on Reusability or Salvage of Used Parts".
- Camshaft followers
- Connecting rods
- Cylinder liners
- Fuel transfer pump
- Oil pump
- Pistons
- Piston pins
- Prelube pump
- Scavenge oil pump
- Turbochargers
Inspect the following components according to the instructions that are in Caterpillar reusability publications. Refer to Guidelines for Reusable Parts and Salvage Operations, SEBF8029, "Index of Publications on Reusability or Salvage of Used Parts".
- Camshaft
- Camshaft bearings
- Crankshaft
- Crankshaft vibration damper
- Driven equipment (alignment)
- Gear train
- Gear train bushings
- Spacer plates
Inspect the camshaft for damage to the journals and the lobes. Inspect the following components for signs of wear and/or for signs of fatigue:
- camshaft bearings
- camshaft followers
Inspect the crankshaft for any of the following conditions:
- deflection
- damage to the journals
- bearing material that has seized to the journals
Check the journal taper and the profile of the crankshaft journals. Check these components by interpreting the wear patterns on the following components:
- rod bearing
- main bearings
Note: If the crankshaft or the camshaft are removed for any reason, use the magnetic particle inspection process to check for cracks.
Replace the crankshaft vibration damper if any of the following conditions occur:
- Engine failure due to a broken crankshaft
- Excessive wear of the front bearing for the crankshaft
- Excessive wear of the gear train that is not caused by a lack of lubrication
Inspect the gears of the gear train and inspect the gear train bushings for the following conditions:
- Worn gear teeth
- Unusual fit
- Unusual wear
In addition to the inspection of components, inspect the alignment of the driven equipment. See the Application and Installation Guide for the engine.
Clean the oil cooler core and the aftercooler core. Then, pressure test both of these cores.
- Remove the core.
- Remove any debris from the core. To remove debris from the oil cooler core, turn the oil cooler core onto one end. To remove debris from the aftercooler core, turn the aftercooler core upside-down.
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NOTICE 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.
- Back flush the core internally with cleaner in order to loosen foreign substances. This will also help to remove oil.
Note: Hydrosolv Liquid Cleaners are recommended. Table 1 lists the Hydrosolv Liquid Cleaners that are available from your Caterpillar dealer.
Show/hide tableTable 1 Hydrosolv Liquid Cleaners(1) Part Number Description Size 1U-8812 Hydrosolv 4165 4 L (1 US gal) 1U-5490 19 L (5 US gal) 8T-7570 208 L (55 US gal) 1U-8804 Hydrosolv 100 4 L (1 US gal) 1U-5492 19 L (5 US gal) 8T-5571 208 L (55 US gal) Show/hide table(1) Use these cleaners at a concentration of two to five percent and at a temperature up to 93 °C (200 °F) . For more information, see Application Guide, NEHS0526, "Service Technical Group". Consult your Caterpillar dealer for assistance. - Steam clean the core in order to remove any residue. Flush the fins of the oil cooler core and the aftercooler core. Remove any other trapped debris.
- Wash the core with hot, soapy water. Rinse the core thoroughly with clean water.
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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.
- Inspect the components in order to ensure cleanliness. Pressure test the core. Many shops that service radiators are equipped to perform pressure tests. Repair the core, if necessary. Install the core.
The concentration of supplemental coolant additive (SCA) should be checked regularly with test kits. The concentration of SCA can also be checked with an S·O·S coolant analysis (Level I). A more detailed coolant analysis is recommended periodically.
For example, considerable deposits are found in the water jacket areas on the external cooling system, but the concentrations of coolant additives were carefully maintained. The coolant water probably contained minerals which were deposited on the engine over time.
A coolant analysis can be conducted in order to verify the condition of the water that is being used in the cooling system. A full water analysis can be obtained by consulting your local water utility company or an agricultural agent. Private laboratories are also available for water analysis.
Caterpillar recommends an S·O·S coolant analysis (Level II).
S·O·S Coolant Analysis (Level II)
An S·O·S coolant analysis (Level II) is a comprehensive coolant analysis which completely analyzes the coolant. An S·O·S coolant analysis (Level II) provides the following information:
- Complete S·O·S coolant analysis (Level I).
- Properties of the coolant are visually inspected.
- Metal corrosion and contaminants are identified.
- Identification of built up impurities that can cause problems BEFORE the problems make repairs necessary.
A report of the results of the S·O·S coolant analysis (Level II) is provided. Maintenance recommendations are based on the results.
For more information about S·O·S coolant analysis, consult your Caterpillar dealer.