What causes high rates of silicon and iron in a cummins diesel?

Answer 1

The high rate of silicon is caused by sand getting into your engine. The question is, what ELSE is in the oil?

If we're looking at iron, chromium and aluminum you've got increased top-end wear, which comes from the intake air. Start by inspecting your air filter; if it looks iffy replace it. Look for damage, cracks, loose hose clamps, etc., in the intake system. If all else fails, idle the engine and block off the air intake. If the engine stalls within 3 seconds you've got no air leaks. Anyway, change the oil, have your compression and blowby tested to be sure your engine isn't ruined, and have the oil retested at 50 hours run time.

If there's lead, tin, copper and aluminum in the sample you've got bearing wear, which means a leaking seal, a defective breather, bad oil filler cap or you're adding oil from a dirty container. For this you find and fix the problem, then do another test at 50 miles. If there's still bearing material in the oil you pull the oil pan and inspect the bearings.

If you have both conditions, and you didn't have any work done to the engine recently, have your mechanic pull the head and inspect the piston tops. There's a phenomenon called piston torching caused by mis-aimed injectors or bad injection timing--basically, the fuel coming out of the injector hits the piston. When this happens it's like having a flamethrower in your engine, except most flamethrowers don't work at as high a pressure as a diesel injection pump does.