The need for an overhaul is generally indicated by increased fuel consumption and by reduced power.
The following factors are important when a decision is being made on the proper time for an engine overhaul:
- The need for preventive maintenance
- The quality of the fuel that is being used
- The operating conditions
- The results of the S·O·S analysis
Oil Consumption as an Overhaul Indicator
Oil consumption, fuel consumption, and maintenance information can be used to estimate the total operating cost for your Cat engine. Oil consumption can also be used to estimate the required capacity of a makeup oil tank that is suitable for the maintenance intervals.
Oil consumption is in proportion to the percentage of the rated engine load. As the percentage of the engine load is increased, the amount of oil that is consumed per hour also increases.
The oil consumption rate (brake-specific oil consumption) is measured in grams per kW/h (lb per bhp). The brake-specific oil consumption (BSOC) depends on the engine load. Consult your Cat dealer for assistance in determining the typical oil consumption rate for your engine.
When an engine's oil consumption has risen to three times the original oil consumption rate due to normal wear, an engine overhaul should be scheduled. There may be a corresponding increase in blowby and a slight increase in fuel consumption.
Using Fuel Consumption For Calculating the Overhaul Intervals
Experience has shown that maintenance intervals are most accurately based on fuel consumption. Fuel consumption corresponds more accurately to the engine load. Table 1 and 2 lists average ranges of fuel consumption for a load factor of approximately 60 percent.
| Service Hours and Fuel Consumption for C27 Generator Set(1) | |||
| Top End Overhaul | 6000 Service Hours | ||
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| Major Overhaul | 12000 Service Hours | ||
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| (1) | Fuel consumption is based on a load factor of approximately 60 percent. |
| Equation For Calculating Overhaul Intervals |
| F/R = H |
| “F” is the estimated total amount of fuel consumption of the engine. |
| “R” is the rate of fuel consumption in liters per hour or gallons per hour. |
| “H” is the number of estimated hours until the overhaul interval. |
Use the actual records of fuel consumption, when possible. If the actual records are not available, use the following procedure in order to estimate the fuel consumption.
- Estimate the average percent of the load for the operation of the engine.
- Refer to the data for fuel consumption in the Technical Marketing Information (TMI) for your engine. This will determine the fuel consumption for the percent of the load that was estimated in Step 1. Use this figure as variable "F" for the equation in Table 2. For more information about the Technical Marketing Information (TMI) for your engine, consult your Cat dealer.
A planned overhaul before failure may be the best value for the following reasons:
- Costly unplanned downtime can be avoided.
- Many original parts can be reused according to the standards for reusable parts.
- The engine service life can be extended without the risk of a major catastrophe due to engine failure.
- The best cost/value relationship per hour of extended life can be attained.
If a major engine failure occurs and the engine must be removed, many options are available. An overhaul should be performed if the engine block or the crankshaft needs to be repaired.
If the engine block is repairable and/or the crankshaft is repairable, the overhaul cost should be between 40 percent and 50 percent of the cost of a new engine with a similar exchange core.
This lower cost can be attributed to three aspects:
- Specially designed Cat engine features
- Cat dealer exchange components
- Caterpillar Inc. remanufactured exchange components
To minimize downtime, a scheduled engine overhaul by your Cat dealer is recommended. This will provide you with the best cost/value relationship.
Note: Overhaul programs vary according to the engine application and according to the dealer that performs the overhaul. Consult your Cat dealer for specific information about the available overhaul programs and about overhaul services for extending the engine life.
If an overhaul is performed without overhaul service from your Cat dealer, be aware of the following maintenance recommendations.
Clean the fuel injector body and replace the O-rings. Replace the O-rings and the gasket on the injector sleeve. Clean the area around the injector seating in the injector sleeve. Refer to the Service Manual for the complete procedure, or consult with your Cat dealer for assistance.
These components should be inspected according to the instructions that are found in various Cat reusability publications. The Special Publication, SEBF8029 lists the reusability publications that are needed for inspecting the engine parts.
If the parts comply with the established inspection specifications that are expressed in the reusable parts guideline, the parts should be reused.
Parts that are not within the established inspection specifications should be dealt with in one of the following manners:
- Salvaging
- Repairing
- Replacing
Using out-of-spec parts can result in the following problems:
- Unscheduled downtime
- Costly repairs
- Damage to other engine parts
- Reduced engine efficiency
- Increased fuel consumption
Reduced engine efficiency and increased fuel consumption translates into higher operating costs. Therefore, Caterpillar Inc. recommends repairing out-of-spec parts or replacing out-of-spec parts.
Piston Rings, Crankshaft Bearings, Valve Rotators, and Crankshaft Seals
The following components may not last until the second overhaul.
- Thrust bearings
- Main bearings
- Rod bearings
- Valve rotators
- Crankshaft seals
- Nonmetallic fuel lines (if equipped)
Caterpillar Inc. recommends the installation of new parts at each overhaul period.
Inspect these parts while the engine is disassembled for an overhaul.
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 is removed for any reason, use the magnetic particle inspection process to check for cracks in the crankshaft.
Inspect the camshaft for damage to the journals and to the lobes.
Note: If the camshaft is removed for any reason, use the magnetic particle inspection process to check for cracks in the camshaft.
Inspect the following components for signs of wear or for signs of scuffing:
- Camshaft bearings
- Camshaft followers
Caterpillar Inc. recommends replacing the crankshaft vibration damper.
During an overhaul, the removal of the oil cooler core is recommended. The oil cooler core and the hould be cleaned and pressure tested.
| NOTICE |
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Do not use caustic cleaners to clean the core. Caustic cleaners can attack the internal metals of the core and cause leakage. |
Note: Use this cleaning procedure to clean the oil cooler core.
- Remove the oil cooler core.
- Remove any debris from the oil cooler core. To remove debris from the oil cooler core, turn the oil cooler core onto one end.
- Flush the oil cooler core internally with cleaner in order to loosen foreign substances. This will also help to remove oil from the oil cooler core.
Note: The use of Hydrosolv Liquid Cleaners is recommended. Table 3 lists the Hydrosolv Liquid Cleaners that are available from your Cat dealer.
Show/hide tableTable 3 Hydrosolv Liquid Cleaners(1) Part Number Description Size 1U-5490 Hydrosolv 4165 19 L (5 US gallon) 174-6854 Hydrosolv 100 19 L (5 US gallon) Show/hide table(1) Use a two to five 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. - Use steam to clean the oil cooler core. This removes any remaining residue from the cleaner. Flush the fins of the oil cooler core. Remove any other trapped debris.
- Wash the oil cooler core with hot, soapy water. Rinse the oil cooler core thoroughly with clean water.
Show/hide table
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 oil cooler core with compressed air. Direct the air in the reverse direction of the normal flow.
- Inspect the components in order to ensure cleanliness. The oil cooler core should be pressure tested. Repair the oil cooler core, if necessary. Install the oil cooler core.
For more information about cleaning the cores, consult your Cat dealer.
The concentration of supplemental coolant additive (SCA) should be checked regularly with test kits or with S·O·S Coolant Analysis (Level 1). Further coolant analysis is recommended when the engine is overhauled.
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 Inc. recommends an S·O·S Coolant Analysis (Level 2).
S·O·S Coolant Analysis (Level 2)
An S·O·S Coolant Analysis (Level 2) is a comprehensive coolant analysis which completely analyzes the coolant and the effects on the cooling system. An S·O·S Coolant Analysis (Level 2) provides the following information:
- Complete S·O·S Coolant Analysis (Level 2)
- Visual inspection of properties
- Identification of metal corrosion
- Identification of contaminants
- Identification of built up impurities (corrosion and scale)
S·O·S Coolant Analysis (Level 2) provides a report of the results of both the analysis and the maintenance recommendations.
For more information about coolant analysis, consult your Cat dealer.