C7 Industrial Engine Operation and Maintenance Manual – Overhaul Considerations

Reduced hours of operation at full load will result in a lower average power demand and reduced fuel consumption. A decreased average power demand should increase both the engine service life and the overhaul interval.

The need for an overhaul is generally indicated by increased fuel consumption, increased oil consumption, excessive engine blowby, and reduced power. Arctic temperatures, extremely high temperatures, corrosive environments, or extremely dusty conditions contribute to premature wear and the need for an overhaul.

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.

Overhaul Options

Before Failure Overhaul

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. 

After Failure Overhaul

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 Caterpillar engine features 
  • Caterpillar dealer exchange components 
  • Caterpillar Inc. remanufactured exchange components 

Overhaul Recommendation

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.

Rebuild or Exchange

Cylinder Head Assembly, Cylinder Packs, Oil Pump, and Fuel Transfer Pump

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.

Inspection and/or Replacement

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 

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 

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.

Oil Cooler Core

During an overhaul, Caterpillar Inc. recommends the removal of the oil cooler core. Clean the oil cooler core. Then, pressure test the oil cooler core.


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.


  1. Remove the oil cooler core.


  1. Remove any debris from the oil cooler core. To remove debris from the oil cooler core, turn the oil cooler core onto one end.


  1. 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: Caterpillar Inc. recommends the use of Hydrosolv Liquid Cleaners. Table 1 lists the Hydrosolv Liquid Cleaners that are available from your Caterpillar dealer.
    Table 1
    HydrosolvLiquid Cleaners
    Part Number Description Size
    1U-8812 Hydrosolv4165 4 L (1 US gallon)
    1U-5490 19 L (5 US gallon)
    8T-7570 208 L (55 US gallon)
    1U-8804 Hydrosolv100 4 L (1 US gallon)
    1U-5492 19 L (5 US gallon)
    8T-5571 208 L (55 US gallon)


  1. 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.


  1. Wash the oil cooler core with hot, soapy water. Rinse the oil cooler core thoroughly with clean water.
  1. Dry the oil cooler core with compressed air. Direct the air in the reverse direction of the normal flow.


  1. 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 Caterpillar dealer.

Obtain Coolant Analysis

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.

For more information about coolant analysis, see your Caterpillar dealer.

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