"I am confused by an oil analysis result I received a few days ago. It was for a sample from a gas engine. The concentration of copper and lead were high, so I decided to dismount the engine and check some of the parts and bearings, but didn't see any abnormal wear. I'm so frustrated. When do you know you need to open an engine in order to prevent catastrophe? In your experience, when is it necessary to open an engine (whether gas or diesel) after having received an oil analysis report?"
Typically, when copper and lead are present in an oil analysis report, it is an indication of bearing wear. Determining whether it is justified to remove the engine and rebuild will require further investigation. Just one oil sample rarely provides enough information to make a diagnosis. You should ask a number of questions before deciding to dig into the engine, such as:
While a rise in copper and lead may be related to bearing wear inside an engine, there are other possible sources. Copper can be found in journal bearings, various bushings, radiators and even as an anti-wear additive in the oil. Lead is primarily used in journal bearings but is also employed as solder in radiators. Any radiator or oil cooler leaching may appear as elevated levels of copper in the report.
To investigate an abnormal result, first make certain the sample was not labeled incorrectly. Communicate with the laboratory to ensure a mistake wasn't made on their end. Another oil sample should be taken to verify the data. If the results are conclusive, additional testing should be performed to find the root cause of the issue. For example, a filtergram could provide helpful information in determining whether the copper and lead results were from bearing wear or a coolant leak.
Examining other elements within the report may reveal more details. If a bearing is wearing to the point of catastrophic failure, the iron content should show a rise in particle count as well. If a coolant leak is present, an elevated potassium result may be shown on the report.
Remember, when using oil analysis as a deciding factor for rebuilding equipment, you first must have sufficient evidence that a rebuild is warranted. This means one test result may not be enough. The full benefits of oil analysis are obtained when a trend can be established and monitored. This may require multiple samples and someone who is well-versed in interpreting the results.