ABYC Diesel Practice Exam

When troubleshooting a sudden oil leak on a mechanical engine, what might cause the dipstick to be pushed out?

1. Low oil level

2. Plugged crankcase breather

3. Oil pump failure

4. Worn engine seals

The correct answer is: Plugged crankcase breather

A dipstick being pushed out during a sudden oil leak on a mechanical engine is often indicative of excessive pressure building up in the crankcase. This condition can occur when the crankcase breather is plugged or obstructed. The breather system is designed to allow gases to escape from the crankcase, which helps maintain a stable pressure within it. When the breather is blocked, the build-up of pressure can force the dipstick out of its tube as a result of the internal pressure exceeding the atmospheric pressure. This situation highlights the importance of having a functioning crankcase ventilation system, as it prevents the accumulation of pressure that can lead to other issues, such as oil leaks or even damage to engine seals and gaskets. While factors like oil level, oil pump functionality, and engine seal wear can contribute to oil leaks or engine issues, they do not directly relate to the pressure buildup that would cause the dipstick to be ejected. Thus, a plugged crankcase breather is the most relevant cause for this particular symptom.