Most vehicle fires originate within the engine compartment. Leakage of fuel, motor oil, transmission fluid, power steering fluid, brake fluid, or even coolant can lead to engine fires, and the leakage of a flammable or combustible liquid in an engine compartment results from some kind of failure. The failure may be a result of normal wear and tear, failure of a mechanic to make repairs safely, design failure which leads to rupture or abrasion of hoses or manufacturing defects in hoses, gaskets or fluid connections. About 15 percent of motor vehicle fires originate in the passenger compartment. The main causes of these are electrical short circuits and cigarettes.
Catalytic converters can generate temperatures high enough to ignite surrounding materials.
When engine control systems malfunction, catalyst operating temperatures can be elevated to a level where the entire catalyst and downstream exhaust pipe glow red hot.