What Are Some Causes of a 3204DT Caterpillar Engine Burning Oil?

by John Willis

Caterpillar is the world's largest manufacture of diesel engines. The Caterpillar 3201DT engine is a diesel power plant used in a number of applications from milling machines to asphalt profiles and track dozers to wheel-loaders. The 3201DT, like all other diesel engines, is apt to smoke under normal operating conditions more than normal gas engines. The 3204DT diesel is also prone to excess smoking for the same reasons all other diesels may smoke; there are several potential causes of excess smoking in diesel engines. The nature of the smoke itself can be a clue to the cause.

Unburned Fuel

Like "gas" engines, diesel engines require a particular ratio of gas and air to function properly. Diesel engines in particular tend to smoke as the engine accelerates because the fuel/air ratio at low RPMs is too rich and cannot be completely burned, whereas at higher RPMS it can be. The excess or unburned diesel fuel causes black smoke. If the smoke is present only during acceleration, it may be normal. If it blows black smoke even at high RPMs, there's probably something else causing the fuel/air mixture to be too rich. A likely cause is air constriction. Less air results in relatively more fuel in the fuel/air mixture. A dirty or clogged air filter is the most common cause.


Gas engines are generally more temperamental than diesels like the 3201DT, which are designed to be rugged, workhorse engines. While a gas engine isn't likely to start if water is present, a diesel may start and run in spite of the water, though it may billow white smoke. It's really not "smoke;" it's water vapor. The water can find its way into the fuel supply in a number of ways, from condensation in air intake to leakage into the fuel tank. Unfortunately, the most common cause of white vapor is a blown head gasket or head, which is a major fix. If vapor is present, shut your motor down until you can determine whether your head and head gasket are okay.

Burned Engine Oil

Blue smoke is the sign of burning engine oil. It indicates major wear on vital engine parts that seal combustion in the combustion chamber. Diesel and gas combustion engines create a lot of friction from metal to metal contact. In spite of cooling and lubrication, parts will eventually wear out. In the presence of blue smoke, the question is "how much wear and on which parts?" If you're lucky, instead of worn rings or cylinders, the problem is stuck rings. Rings make the pistons seal tight to the cylinder walls. They sit in grooves in the piston. If carbon builds in the groove, sometimes known as a "burnt ring," the small amount of flex and expansion in the ring becomes frozen, letting engine gasses by as if it were worn. Engine treatment products are available to cure this problem. The rings can be mechanically cleaned, but an oil additive may save you the time and expense. The other option probably includes honing or boring the cylinders, and replacing your pistons and rings.

Worn Rings and Cylinder

Valves also wear out. Like pistons and rings, valves create a seal in the engine. If the valves or valve seats are worn, the engine will smoke. The only remedy is to rebuild the valve train. The valve train and pistons and rings don't necessarily wear evenly. Previous replacement of rings might leave them in good condition. So, it's possible to require valves that need to be rebuilt and pistons and rings that are in working order.

About the Author

John Willis founded a publishing company in 1993, co-writing and publishing guidebooks in Portland, OR. His articles have appeared in national publications, including the "Wall Street Journal." With expertise in marketing, publishing, advertising and public relations, John has founded four writing-related ventures. He studied economics, art and writing at Portland State University and the Pacific Northwest College of Art.