The need for a major overhaul is determined by several factors.
- An increase of oil consumption
- An increase of crankcase blowby
- The total amount of fuel consumption
- 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 require service. An increase in the levels of noise and vibration indicates that rotating parts require service.
Note: Oil analysis may 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 your Cat dealer 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.
A major overhaul includes all the work that is done for the top end overhaul. A major overhaul includes more parts and labor. More parts and labor are required to rebuild the engine.
For the major overhaul, all the bearings, seals, gaskets, and components that wear are disassembled. The parts are cleaned and inspected. If necessary, the parts are replaced. The crankshaft is measured for wear. The crankshaft may require regrinding. Alternatively, the crankshaft may be replaced with a Cat replacement part.
Your Cat dealer can provide these services and components. Your Cat dealer can ensure that the components are operating within the appropriate specifications.
| Overhaul Schedule
First Occurrence Following Intermediate Overhaul |
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| Fuel Consumption | |
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| Load Factor | < 25 Per Cent | 25 - 30 Per Cent | 30 - 50 Per Cent | > 40 Per Cent |
| Service Hours | 24000 | 21000 | 18500 | 16000 |
| Load Cycles(1)(2) | 192000 | 192000 | 192000 | 192000 |
| (1) | To illustrate engine capability, a load cycle has been defined as an increase of at least an 80 per cent rated power followed by a decrease of at least 80 per cent rated power. Load cycles of less than 80 per cent rated power may also impact the engine overhaul interval, requiring your specific operating profile to determine your appropriate interval. |
| (2) | Determining the appropriate overhaul interval will require understanding of the locomotive operating profile including total operating hours, amount of fuel burned, load factor, load cycles, and total number of engine starts. Caterpillar requires the use of data recorders to help determine the operating profile and to set appropriate intervals for a fleet on a given route. Changes in operating profiles (a different deployment or change in the operating profile for the existing route) may require adjustment of overhaul intervals to ensure reliable performance. Failure to follow the overhaul intervals may result in unplanned repairs. For assistance with calculating load cycles, installing data recording equipment and/or confirming overhaul intervals, contact your Cat dealer. |
Inspect 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".
- Aftertreatment dosing cabinet
- Aftertreatment CEM
- Camshaft
- Coolant (SCA) temperature regulator (ESTAT)
- Crankshaft
- Driven equipment (Alignment)
- Engine cylinder block
- Flywheel
- High-pressure fuel lines
- Rear gear train
- Oil suction screen
Reconditioning or Exchanging of Components
Inspect 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".
Recondition the worn components or exchange the components, if necessary. Your Cat dealer can provide these services and components.
- Aftertreatment DEF injector
- Aftertreatment DEF pump
- Camshaft followers
- Connecting rods
- Coolant (SCA) temperature regulator (ESTAT)
- Cooling system including, tubes, brackets, clips, housings, and elbows
- Crankshaft vibration damper
- Cylinder head assembly
- Cylinder liners
- Engine mounts
- Exhaust manifolds
- Fuel pressure regulating valve
- Fuel transfer pump
- Jacket water pump
- Oil cooler bypass valve
- Oil cooler core
- Oil lubrication system including tubes, brackets, clips, housings, and elbows
- Oil pressure regulating valve
- Oil Prelube pump
- Oil pump
- Piston pins
- Rocker arms
- SCAC water pump
- Software update
- Starter motor
Replace the following components during the major overhaul:
- Aftercooler core
- Aftercooler gaskets and air inlet bolts
- Aftertreatment air regulator
- Aftertreatment air strainer
- Aftertreatment catalysts
- Aftertreatment CEM sensors and harnesses
- Aftertreatment DEF strainer
- Aftertreatment dosing cabinet sensors, harnesses, and solenoid valves
- Aftertreatment sensors including temperature, DEF level, and pressure
- Air inlet compression bellows
- Air inlet manifold gaskets and seals
- Camshaft bearings
- Camshaft thrust washers
- Connecting rod bearings
- Coolant (SCA) temperature regulator (ESTAT)
- Crankshaft seals
- Crankshaft thrust washers
- Engine control module
- Engine sensors - level, pressure, speed, and temperature
- Engine wiring harness
- Exhaust bellow shields
- Exhaust manifold bellows, clamps, and bolts
- Exhaust manifold (Turbine inlet) supports and hardware
- Exhaust manifold seals
- Flexible pipe bellow, turbine outlet elbows, and clamps
- Flexible pipe heat shielding
- Flywheel ring gear
- Front gear train
- Fuel accumulator
- Fuel boost pump
- Fuel injector
- Fuel priming solenoid
- Gear train bushings and bearings
- Main bearings
- Pistons
- Piston rings
- Torsional coupling
- Turbochargers
Clean the oil cooler core and the aftercooler core. Then, pressure test both of these cores. For instructions on cleaning the cores, see this Operation and Maintenance Manual, "Aftercooler Core - Inspect/Clean" topic.
Clean the oil suction screen. Also, remove side covers to clean the oil sump. For instructions on removal and installation of components, see the Service Manual, "Disassembly and Assembly" module.
For conventional heavy-duty antifreeze/coolant, check the concentration of supplemental coolant additive (SCA) regularly. The concentration of SCA can be checked with an S·O·S coolant analysis (Level 1). 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 to verify the condition of the water that is being used in the cooling system. A full water analysis may be obtained from the following sources:
- Cat dealer
- Local water utility company
- Agricultural agent
- Independent laboratory
Caterpillar recommends an S·O·S coolant analysis (Level II) which is a comprehensive chemical evaluation of the coolant. This analysis is also a check of the overall condition inside the cooling system. The following services are provided:
- Full Level 1 analysis
- Identification of the source of metal corrosion and of contaminants
- Identification of buildup of the impurities that cause corrosion
- Identification of buildup of the impurities that cause scaling
- Determination of possible electrolysis within the engine cooling system
A report of the results of the analysis is provided. Maintenance recommendations are based on the results.
For more information about S·O·S coolant analysis, consult your Cat dealer.