C27 and C32 Industrial Engines Caterpillar

Overhaul (Major)

Usage:

C27 AT4

Note: Fuel consumption in this Operation and Maintenance Manual, "Maintenance Interval Schedule" is based on a load factor of approximately 40 percent.

Refer to this Operation and Maintenance Manual in order to determine the maintenance interval for a major overhaul.

The need for a major overhaul is determined by several factors.

An increase of oil consumption
An increase of crankcase blowby
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 require 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.

A major overhaul includes all of the work that is done for the top end overhaul and the general inspection. A major overhaul includes additional parts and labor. Additional parts and labor are required in order to rebuild the engine.

For the major overhaul, all of 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.

If you elect to perform an overhaul without the services of a Cat dealer, be aware of the following recommendations.

Replacement of Components

Replace the following components during the major overhaul.

Connecting rod bearings
Crankshaft seals
Crankshaft vibration damper
Electronic fuel injectors
Main bearings
Piston rings
Nonmetallic fuel lines (if equipped)
Clean emissions module

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.

Camshaft followers
Connecting rods
Cylinder head assembly
Cylinder liners
Engine wiring harness
Exhaust bellows
Fuel transfer pump
Oil pump
Pistons
Piston pins
Prelube pump
Spacer plate
Turbochargers

Inspection of Components

Camshaft
Camshaft bearings
Crankshaft
Crankshaft thrust washers
Driven equipment (alignment)
Engine control module
Front gear train
Gear train bushings and bearings
Rear gear train

Inspect the camshaft for damage to the journals and the lobes. Inspect the following components for signs of wear and/or for signs of fatigue:

camshaft bearings
camshaft followers

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 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 occur:

Engine failure due to a broken crankshaft
Excessive wear of the front bearing for the crankshaft
Excessive wear of the gear train that is not caused by a lack of lubrication

Inspect the gears of the gear train and inspect the gear train bushings for the following conditions:

Worn gear teeth
Unusual fit
Unusual wear

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.

Cleaning of Components

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 - Clean/Test" topic.

Clean the oil suction screen. Also, remove side covers in order to clean the oil sump. For instructions on removal and installation of components, see the Service Manual, "Disassembly and Assembly" module.

Obtain a Coolant Analysis

For conventional heavy-duty coolant or 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 One). 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 probably contained minerals which 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 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 Two). This analysis is a comprehensive chemical evaluation of the coolant. This analysis is also a check of the overall condition of the inside of the cooling system. The following services are provided: