Procedure To Clean Oil Passages In Crankshafts And Cylinder Blocks

All Engines

It is Caterpillar’s recommendation that the procedure that follows should be used to clean all new, used (crankshafts and cylinder blocks that are to be used again) and reconditioned crankshafts and cylinder blocks before they are assembled.

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) is a product of fuel combustion that, over a long period of time, has mixed with oil and become thick. Most of the time this debris can not be removed completely when only a high pressure wash or a high pressure nozzle is used to clean the oil passages.

Debris (chips or abrasive material from the reconditioning operation) that is not removed after an engine or bearing failure or after a reconditioning operation can also cause early engine failure. It is important that all debris is removed from the oil passages in the crankshaft and cylinder block. Larger particles of debris can cause damage to the crankshaft journal and bearings when the engine is first started because the bypass valve can let unfiltered oil get in to the engine. See Illustration 1.

Illustration 1.

Use the following procedure to make sure the oil passages in the crankshaft and cylinder block are free of debris:

1. Remove all plugs. Allen head plugs may have to be drilled and removed with a 6.35 mm (.25″) Easy Out Remover. Most lightening hole core plugs are held in position with snap rings. These snap rings can be removed with two screwdrivers or can be cut in half with a cold chisel. Cylinder block plugs and similar plugs in older crankshafts can also be removed with a cold chisel.

2. Install one of the brushes from the chart in a variable speed drill. Use a brush that has a diameter that is just larger than the diameter of the oil passage to be cleaned.

3. Use a petroleum solvent and one of the brushes from the chart to loosen any debris or carbon (deposits) in all the oil passages in the crankshaft and cylinder block. See Illustration 2. Make sure the end of the brush goes to the end of each oil passage. Each oil passage must be cleaned from every possible direction. 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 3.

Illustration 2.

Illustration 3.

4. Use the brush and a solution of detergent and water to “float” the debris out of the oil passages. Use water to wash the rest of the detergent and water solution out of the oil passages and then use an air hose to dry the cylinder block or crankshaft.

5. If the crankshaft and cylinder block are not going to be used immediately, put a rust inhibitor on the crankshaft and cylinder block to prevent damage.

6. Make sure the rust inhibitor is removed before the crankshaft is installed in the cylinder block.

7. Install all the plugs in the crankshaft and cylinder block. See the Specifications section of the Service Manual for the correct torques and procedures for the installation of the plugs in the crankshaft and cylinder block.

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