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:
- Need for preventive maintenance
- Quality of the fuel that is being used
- Operating conditions
- 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:
- Avoid costly unplanned downtime.
- Reuse many original parts according to the standards for reusable parts.
- Extend the engine's service life without the risk of a major catastrophe due to engine failure.
- Attain the best cost/value relationship per hour of extended life.
Many options are available if a major engine failure occurs. 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 Caterpillar engine features
- Caterpillar dealer exchange components
- Caterpillar 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.
Inspect the following components 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.
- Cylinder head assembly
- Connecting rods
- Pistons
- Turbocharger
- Oil pump
- Fuel ratio control
- Cam followers
- Fuel transfer pump
- Timing advance
- Valve rotators
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 salvaged, repaired, or replaced.
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.
Replace the following components during the overhaul:
- Piston rings
- Thrust bearings
- Main bearings
- Connecting rod bearings
- Gaskets and seals
- Engine mounts
- Hoses
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
- Gear train
Inspect the camshaft for damage to the journals and the lobes. Inspect the camshaft bearings for signs of wear and/or for signs of fatigue.
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 rod bearings and 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 are found:
- Engine failure due to a broken crankshaft
- Excessive wear of the front main bearing
- Excessive wear of the gear train that is not caused by a lack of lubrication
- Visconic damper that is dented, cracked, or leaking
- Visconic damper that is discolored from heat
- Rubber damper that is deteriorated and cracked
- Rubber damper with slippage of the outer ring
Inspect the gear train for the following conditions:
- Worn gear teeth
- Unusual fit
- Unusual wear
Test the following components during the overhaul:
- Fuel injection nozzles
- Fuel injection pump
- Governor
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.
The following components should be cleaned and pressure tested during the overhaul:
- Engine oil cooler
- Aftercooler
Refer to the Operation and Maintenance Manual, "Aftercooler Core - Inpect/Clean" topic (Maintenance Section) for the cleaning procedure.
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.
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 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 1)
- 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 that are based on the analysis.
For more information about coolant analysis, consult your Caterpillar dealer.