The main cause of recent fires in BMW cars turned out to be in faulty exhaust gas recirculation (EGR) valves, not the bypass as claimed by the German automaker claimed in August, investigation showed Wednesday.

According to interim investigation results announced by Korea Transportation Safety Authority on Wednesday, the cause of fires in BMW cars laid with faulty EGR valves, not EGR bypass claimed by BMW.

The latest finding is raising concerns over the possibility of other fire-catching elements which could lead to additional recalls. In July, BMW recalled a total 106,317 vehicles from 42 models, the largest recall thus far by a foreign auto brand in Korea. The German automaker issued an additional recall on 65,763 vehicles in October.

The public-private investigation team led by the authority consisting of experts in specific fields carried out experiments to test the cause of production defect in relation to the fires and possibility of further ignitions.

The experiments showed that BMW cars catch fire when all three conditions are met - when there is a leak in EGR cooler, when the EGR valve is partially set to be left open and the car drives in high speed, and when diesel particulate-NOx reduction system is in operation.

In such an environment, the deposits due to EGR cooler leakage meet with high temperature exhaust emissions coming in through EGR valves, triggering sparks, and spreading bigger inside engine room induction system. The spark becomes bigger when it contacts air in high-speed driving environment and creates a hole in the induction system to spread and move onto the engine room to cause fire.

The latest interim finding is different from what BMW had announced in August, the investigation team said.

Back then, BMW claimed the fires were caused by opened EGR bypass valves and EGR cooler leakage in high mileage cars while driving in high speed.

The public-private investigation team, however, confirmed that EGR bypass has no relation to the cause of the fires and rather EGR valves in which BMW had not pointed out.

By Yong Hwan-jin and Lee Eun-joo

[ⓒ Pulse by Maeil Business Newspaper & mk.co.kr, All rights reserved]