TUBE AS 4680990 - Caterpillar

reports occasionally identify the cause of rod bearing failures as "unexplained" lack of lubrication. A preliminary examination of engine maintenance and work application provides no obvious explanation for bearing damage and/or failure.
Caterpillar believes that most failures caused by marginal lubrication conditions will fall into one or more of the following categories.
1. Low Oil Level - Engines with excessive oil consumption or serious leaks are prime suspects.2. Quick Starts After Oil Change - The empty oil filter can cause a delay in engine oil pressure and can cause bearing damage. Always crank the engine with fuel shut off to develop oil pressure, or start engine at low idle rpm.3. Cold Starts - Repeated rapid starts to high idle rpm (to get air tanks filled, etc.) can damage crankshaft bearings, especially in cold temperatures with heavier grades of lubrication oil such as SAE 30 or SAE 40 oil.4. Dry Starts - Engines should be pressure lubricated after a rebuild or after not being used for 30 days or more prior to starting the engine.5. Operating On Excessive Slopes - Industrial, marine and generator set engines should be installed and operated within specifications relating to tilt or slope of the engine and maintain the required lubrication overfill volumes that are specified.6. Running Engine Backwards - Several conditions can lead to opposite rotation of the crankshaft, most of these occurring when there is excessive engine load at low idle rpm. See Engine News, December 12, 1984, page 2, "Causes And Correction Of Opposite Crankshaft Rotation In Direct Injection Engines".7. Dilution of Lubrication Oil - Fuel/coolant dilution can be a contributor to lack of lube failures.8. Other Parts Failures - Failures of other components such as oil pump, oil lines or bypass valves are not normal causes, but they are possible and can be verified.Another question frequently asked is, "Can the lead-tin overlay (LTO) smearing of crankshaft bearings be caused from the clearance and loss of oil pressure from a spun bearing?" Caterpillar engines may see a pressure drop from the failed bearing, but Caterpillar believes the oil pump is designed with enough capacity to handle a single bearing failure without significant loss of engine oil pressure. Also, as the above list indicates, a failure may result many miles after a set of bearings has been smeared or scuffed from a lack of lube condition. A bearing inspection is recommended when any lack of lube condition occurs.