What Causes Blue Smoke from a BMW?
1 Answers
The main reason for blue smoke from a BMW is the entry of engine oil into the combustion chamber, where it participates in combustion. Reasons for oil entering the combustion chamber include: 1. Incorrect oil viscosity selection: Manifested as no blue smoke during cold starts in the morning, but slight blue smoke emission after the engine warms up. There was no blue smoke before, but it appears after switching to another type of oil. There is acceleration functionality, but oil consumption is too fast, and engine noise increases. 2. Carbon deposits cause the piston rings to lose tension and fail to seal properly, allowing oil to enter the cylinder through the gaps: Little to no blue smoke during cold starts in the morning, but more blue smoke appears mainly during acceleration and after the engine warms up. Power decreases, cylinder pressure sealing performance declines, and oil consumption relatively increases. 3. Aging and hardening of valve stem seals prevent them from expanding and contracting with the temperature of the valves, causing oil to enter the cylinder from the seals during cold starts: Manifested as blue smoke during cold starts in the morning but none after the engine warms up, with excessive oil consumption. 4. Sticking of the PCV valve allows combustible mixture to leak into the crankcase, thinning and deteriorating the oil, which then enters the combustion chamber, accelerating oil consumption: The power decline period of the oil and consumption speed up, with noticeably insufficient power.
