Procedure To Clean Oil Passages In Crankshafts And Cylinder Blocks

All Engines

Cleanliness is a major factor in preventing bearing failures. Do not assemble debris into the engine. Successful overhauls demand clean work areas and clean components for assembly. It is important that the correct procedures and tools are used to achieve the desired cleanliness.

Cleanliness must start with the disassembly of the engine. First, use a steam cleaner or similar equipment to clean the external surface of the engine. This will help keep the assembly area clean and reduce the chance of contamination in an assembled engine. Use plastic plugs and covers to prevent debris from entering the disassembled engine components. Use the correct tools, lifting devices and storage racks to avoid damage and protect the engine components.

One reason for bearing failure after an engine overhaul is debris that was not removed from the oil passages in the crankshaft and cylinder block. Some of this debris (carbon deposits or sludge) is a product of fuel combustion that, over a long period of time, mixes with oil and becomes thick.

Another source of debris is metal chips or abrasive material that is not removed after an engine or bearing failure or after a reconditioning operation. This debris can cause damage to the bearing journals and bearings when the engine is first started.

Extra care must be taken after a bearing failure to make sure all the debris and bearing material is removed from the entire engine lubrication system. The crankshaft oil passages must be cleaned. All plugs, orifice dowels, cooling jets and hoses must be removed from the block so the oil passages can be cleaned. Remove auxiliary equipment that is lubricated by the engine oil. Disassemble this eqiupment and clean the oil passages.

Equipment For Cleaning

It is important that all debris is removed from the oil passages in the crankshaft and cylinder block. Cleaning must be complete and thorough, because cleaning that is not thorough may only result in loosening debris, allowing it to break free and damage bearings and other components after the engine is put into service.

Oil passages must be thoroughly cleaned with brushes to make sure all carbon deposits (sludge) and debris are removed. Good quality brushes are required. The following brushes are available from Caterpillar and are in sizes that will clean all current engine blocks and crankshafts.

NOTE: When the main oil passage in the cylinder block is cleaned, it will be necessary to weld a 3.18 mm (.125″) mild steel rod to the end of the brush handle. Make sure the rod is long enough to let the brush go all the way through the cylinder block. See Illustration 1.

Illustration 1. Weld a steel rod to brushes used to clean long passages such as the main oil gallery in cylinder blocks.

Most of the time debris can not be removed completely when only a high pressure wash or a high pressure nozzle is used to clean the oil passages. A nozzle with a high aerated flow or pulsating flow is recommended. One aerated nozzle that can be used is the “Jumbo Jiffy Gun” with “Air Boost.” Parts for this tool are shown in the chart that follows.

Use a 2 to 3% (by volume) alkaline type cleaning solution (detergent) with the cleaning gun (aerated nozzle). The temperature of the cleaning solution must be 43 to 55°C (110 to 150°F).

Special Instructions will be available to give more detailed information about the cleaning equipment and procedures.

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