The need for a major overhaul is determined by several factors.
- An increase of oil consumption
- An increase of crankcase blow-by
- 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 need servicing. An increase in the levels of noise and vibration indicates that rotating parts require service.
Note: Oil analysis can 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.
For the 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.
Replacement of the following components is recommended at major overhaul.
- Air shutoff
- Bellows, clamps, and hardware
- EGR and ERV valves actuator assemblies
- Exhaust and inlet manifold seals and gaskets
- Exhaust manifolds 1, 3, 11, and slip fit exhaust joints
- Hump hoses
Gaskets, Seals, and O-rings
- Bearings
- Thrust plates
- O-rings, retaining rings, clamps, grommets, and gaskets
- Crankshaft seals
- Thrust washers
- Main bearings
- Cylinder head gasket
- Ferrules
- Shim gasket
- Stem seals
- ECM harness
- Grommets, tie straps, ladder clips
- Harness heat shielding
- Seals, gaskets, and o-rings
- Fuel
- Pressure
- Temperature
- Speed
- Accumulators
- High-pressure fuel pump
- Injectors
- Seals, gaskets, and o-rings
- Sensors
- Bearings
- Bushings, thrust plates, and thrust washers
- Piston rings
- Rod bearings
- Seals
- Adjusting screws
- HLA pushrods
- Oil dowel
Inspection, 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.
In addition to the inspection of components, inspect the alignment of the driven equipment. See the Application and Installation Guide for the engine or see the literature that is provided by the OEM of the driven equipment.
- Diesel Oxidation Catalyst (DOC)
- EGR and ERV valves
- Heat shields
- Inlet piping
- Turbocharger
- Cylinder block
- Driven equipment alignment
- Engine mounts
Inspect the camshaft for damage to the journals and lobes.
Use a magnetic particle inspection process to check for cracks in the camshaft.
Inspect the followers.
- Aftercooler core
- Jacket water pump
- Lines and castings
- NRS coolers
- Oil cooler core
- Oil pump
- Oil suction screen
- Scavenge pump
- Thermostats
Use the magnetic particle inspection process to check for cracks.
Inspect the following:
- Bearing material seized in journals
- Damage to journals
- Deflection
- Taper and profile of crankshaft journals for wear caused by rod bearings and main bearings
- Unusual wear patterns of rod bearings and main bearings may require investigation
Replace 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 front gear train that is not caused by lack of lubrication
- Cylinder head assembly
- Inspect and clean accumulator and injector bore
- Spacer plate
- Alternator
- Engine Control Module (ECM)
- Main engine harness
- Software update
- Check valves and regulating valves
- Clean the fuel module pump
- Fuel transfer pump
- High-pressure fuel lines
- High-pressure pump screen
- Low-pressure lines
- Priming pump
- Secondary filter canister and base
- Flywheel
- Front and rear gears (inspect for worn gear teeth, unusual fit, and unusual wear)
- Connecting rods
- Liners
- Pistons
- Piston pins
- Bridges
- Harness
- Rocker arms
- Rocker box and posts
- Rocker shaft
- Seals
- Starters
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.
Clean the high-pressure fuel pump (HPFP) oil screen. Refer to the Disassembly and Assembly manual for more information.
For conventional heavy-duty coolant/antifreeze, 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). This analysis 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.
Inspect the cylinder head assembly 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".
Your Cat dealer can provide these services and components. Your Cat dealer can ensure that the components are operating within the appropriate specifications.
The use of out-of-spec parts will cause unscheduled downtime and/or costly repairs.
Replace the injectors. Consult your Cat dealer about exchanging the injectors. Your Cat dealer can provide these services and components.
The wear of injectors is affected by the following considerations:
- Quality of the fuel
- Quality of the filtration of the fuel
The wear of the injectors can result in elevated levels of exhaust emissions and/or poor engine performance. The misfire of a single cylinder is not typically attributed to normal wear. This condition can be repaired by replacing the faulty injector.
The following circumstances can indicate that the injectors should be inspected more frequently:
- Use of fuels that are not recommended in this Operation and Maintenance Manual, "Refill Capacities and Recommendations"
- Extreme ambient temperatures that reduce the ability of the fuel to provide lubrication
- Frequent plugging of the fuel filters
- Insufficient maintenance of the fuel tank or the fuel storage tank that can allow excessive water, sediment, and other contaminants.
- Insufficient maintenance of the fuel filters
Clean the oil suction screen after the oil has been drained.
- Remove the screen assembly according to the instructions in the Service Manual, "Disassembly and Assembly" module. Discard the used O-ring seals.
- Wash the screen assembly in clean nonflammable solvent. Allow the screen assembly to dry before installation.
- Remove side covers to gain access to the sump. Clean the bottom of the sump with absorbent towels or pillows. When the bottom of the sump is clean, install the side covers.
- Inspect the screen assembly for good condition. Obtain a new screen assembly, if necessary. Install the screen assembly. Install new O-ring seals.
Note: Approximately