Tech Tip: Diagnosing Oil Leakages with Turbochargers

If you’ve ever had a turbocharger start leaking or smoking, you may have thought the turbocharger was faulty. This is a common misperception, but, most of the time it has nothing to do with the turbocharger functionality. More than 95 percent of the time, oil leakage is caused by a few issues:

• Oil drain line that is too small
• Oil drain line restricting oil flow
• Excessive blow-by

1. Check the size of the oil drain line. It should be equal to or larger than the bearing housing oil drain—and, the larger the oil drain, the better (within reason). “The inner diameter of the pipe should not be smaller than the drain hole in the bearing housing because this could cause the oil to back up and leak into the end housings,” says Seth Temple, Senior Application Engineer. “If the drain line is smaller than the hole size, then it can create restrictions.” He also recommends making sure the gasket is equally sized.
2. Check to see how the oil is returning back to the engine. The oil drain line should be straight and downhill, with no level spots or upturns, to remain free-flowing with no restrictions. It’s important to avoid 90° bends, so the drain line can enter the oil pan above the static oil line and not in line with the throw of the crank. “The goal is to make sure the oil flows freely to the top of the oil pan with no restrictions,” Temple says. “So, it’s critical the oil line is as vertical as possible to promote good oil flow. If you have restriction in the oil drain line, oil can back up and leak out of the compressor or turbine end. The oil will follow the path of least resistance.”
3. Check to see if the engine has excess crankcase pressure/blow-by. If the engine has high mileage and is in need of rebuilding, this can cause excessive blow-by. This essentially creates a higher pressure or restriction in the oil drain and does not promote good oil flow, causing the oil to follow the least path of resistance. If you follow these steps and determine it is not an improperly sized or restricted oil line, or excessive blow-by, then the leakage also may be due to excessive tilt of the turbocharger, a damaged bearing system, or worn or collapsed piston rings.