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 Caterpillar 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 Caterpillar 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.
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's 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.
Many options are available if a major engine failure occurs. An overhaul should be performed if the engine block or the crankshaft can be repaired.
If the engine block is repairable and/or the crankshaft is repairable, the overhaul cost should be less than the cost of a new engine with a similar exchange core.
This lower cost can be attributed to these aspects:
- Caterpillar dealer exchange components
- Caterpillar Inc. remanufactured exchange components
To minimize downtime, Caterpillar Inc. recommends a scheduled engine overhaul by your Caterpillar dealer before the engine fails. 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 Caterpillar 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 Caterpillar dealer, be aware of the following maintenance recommendations.
These components should be inspected according to the instructions that are found in various Caterpillar 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.
The following components may not last until the second overhaul.
- Piston rings
- Thrust bearings
- Main bearings
- Connecting rod bearings
- Crankshaft seals
- Engine mounts
- Hoses
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
- Valve lifters
Test the following components during the overhaul.
- Fuel injection nozzles
- Fuel injection pump
Testing the fuel system during the overhaul will ensure that your engine operates at peak efficiency. Your Caterpillar dealer can provide these services and components in order to ensure that your fuel system is operating within the appropriate specifications.
Caterpillar Inc. recommends the use of Hydrosolv Liquid Cleaners. Table 1 lists the Hydrosolv Liquid Cleaners that are available from your Caterpillar dealer.
| HydrosolvLiquid Cleaners | ||
| Part Number | Description | Size |
| 1U-8812 | Hydrosolv4165 | |
| 1U-5490 | |
|
| 8T-7570 | |
|
| 1U-8804 | Hydrosolv100 | |
| 1U-5492 | |
|
| 8T-5571 | |
|
The concentration of supplemental coolant additive (SCA) should be checked regularly with test kits or with S·O·S Coolant Analysis (Level I). Further coolant analysis is recommended when the engine is overhauled.
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 that 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 Inc. 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 and the effects on the cooling system. An S·O·S Coolant Analysis (Level II) provides the following information:
- Complete S·O·S Coolant Analysis (Level I)
- 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 II) provides a report of the results of both the analysis and the maintenance recommendations.
For more information about coolant analysis, see your Caterpillar dealer.