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. These parts are available from:

The Elliott Company
1809 Sheridan Avenue
Springfield, OH 45505 U.S.A.
Telex: (810) 452-2865
Telephone: (513) 324-4191

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.

Cleaning Procedure For Cylinder Blocks And Crankshafts

Caterpillar recommends to use the procedure that follows to clean the oil passages in all new, used and reconditioned crankshafts and cylinder blocks.

1. Use steam cleaning or a similar method to remove as much external dirt, oil or preservative coating as possible.

2. Remove all covers and plugs from the oil passages. See Guideline For Reusable Parts, Visual Inspection Of Crankshafts, Form SEBF8043 for information about crankshaft plug removal.

3. Position cylinder blocks upside down (oil pan rails up).

4. Use a petroleum base cleaning solvent and the correct size brush in a variable speed drill to loosen debris or carbon deposits (sludge) in all crankshaft or cylinder block oil passages. Operate the drill at approximately 300 rpm. The diameter of the brush must be slightly larger than the diameter of the oil passage that is to be cleaned. Make sure the end of the brush goes to the end of each oil passage. Each oil passage must be cleaned vigorously and repeatedly from every possible direction.

5. After most of the debris has been removed using the brush and petroleum base cleaning solvent, use the brush and a solution of detergent and water to clean out all visible debris.

6. After brushing, use the aerated nozzle (“Jiffy Gun”) and hot alkaline type cleaning solution to clean and flush all debris from the oil passages.

7. Flush auxiliary passages toward the main oil gallery, then flush the main gallery from one end. Flush all main galleries such as the camshaft bores in a similar manner. Always flush out the main galleries last, to wash away debris flushed from the auxiliary passages.

8. One major source of debris that is not obvious is small metal particles that are created when pipe plugs and other plugs are installed. The following procedure will reduce the dangers from this source.


a. Clean the cylinder block or crankshaft first with all plugs removed.

b. Use a small brush to clean the threads of each plug and tapped hole; use detergent and water. If threads are damaged or have burrs, use a tap to clean and repair them. Then clean the threads and passages again with a brush and use the aerated nozzle (“Jiffy Gun”) to flush the passages.

c. Install all plugs in the crankshaft and cylinder block. Be sure the correct plugs are used. Tighten each plug to its correct torque. See the appropriate Service Manual module.

d. Repeat flushing of the main galleries (after the plugs are installed) with the aerated nozzle and cleaning solution to remove particles caused by installation of the plugs. (Although auxiliary passages can only be flushed from one end, this operation will usually be adequate and better than not flushing after the installation of the plugs).

9. Use clean water under pressure to flush the rest of the detergent and water solution out of the oil passages. Then use air pressure to dry the cylinder block or crankshaft. (Do not allow surfaces to dry by evaporation. Corrosion and rust are more likely).

10. If the crankshaft or cylinder block is not to be used immediately, flush the oil passages with clean oil and put plastic plugs in all oil passage openings. Put a rust inhibitor over the complete cylinder block or crankshaft. Put the crankshaft or cylinder block in VCI (volatile corrosion inhibitor) storage bags for long term storage (more than 30 days). For more information about rust inhibitor materials, contact the local Caterpillar Dealer.

11. Before a crankshaft or cylinder block (that is new or has been in storage) is put into service, be sure to remove all plastic plugs and rust inhibitor. Flush out the oil passages. Then dry and lubricate as necessary before installation.

Precautions For Engine Start-Up

It is very important for an engine to have adequate (needed) lubrication during the first seconds of operation. A “dry start” (without needed lubrication) of an engine can cause bearing damage. An engine generally has enough oil on the parts for lubrication during engine start-up; however, this lubrication may not be enough or may be lost if the engine has been in storage for any length of time. To prevent the possibility of a “dry start” and bearing damage during the first seconds of operation, pressure lubrication of the engine is necessary (fill the main oil passages with oil under pressure).

Special Instruction, Form SMHS7701, gives the pressure lubrication procedure for engines.

Engine Maintenance

It is essential to bearing performance that the lubrication system be maintained properly. This maintenance will help keep the oil clean and free of contamination. Correct maintenance includes …

using oil of the correct grade and viscosity
maintaining the correct oil level
adhering to the recommended oil and filter change intervals
using the correct oil filter; one known to be high quality

The appropriate Operation and Maintenance or Lubrication and Maintenance Guide will give recommendations for oil grade, viscosity and change intervals. Use of the correct Caterpillar filter is the best way to make sure filter performance is satisfactory.


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