Engine Compartment Fire

On April 30, 2018, Mercedes-Benz USA, LLC, (Mercedes-Benz) submitted a Defect Information Report (DIR) to NHTSA regarding a defect that could result in a vehicle fire starting from the engine compartment in 42,781 model year (MY) 2008 and 2009 Smart Fortwo cabrio and coupe vehicles (451 platform). According to Mercedes-Benz’s DIR, “the rear insulation mat within the engine compartment might deform, deteriorate, loosen and over time, subsequently be able to contact hot components of the exhaust system. This could lead to an ignition of the insulation mat and possible fire in the engine compartment.” The US-specification exhaust system has an external catalytic converter packaged close to the insulation mat, where temperatures in the vicinity of the insulation mat reach high values. Over time, these temperatures can lead to a change in the insulation mat's material characteristics and ultimately allow the material to deform. Depending on the magnitude and the specific location of the deformation, the insulation mat could contact hot components of the exhaust system and ignite. Mercedes-Benz will replace the rear insulation mat on the affected vehicles with the improved mat first implemented in the United States in MY 2010 vehicles. ODI’s analysis of fire incident field data reported to NHTSA and Mercedes-Benz show an increasing trend of non-crash fires in the subject vehicles that begins after 4 years of service and accelerates after 7 years of service. The analysis shows that this trend is driven by fires occurring in the engine compartment. Forensic investigations of fires occurring in the past year identified the insulation mat as a likely or possible cause of most of the fires originating in the engine compartment. This investigation is closed based on Mercedes-Benz insulation mat recall. For more information about field data trends and fire investigations, see the closing resume in the document file for this investigation.