Where Car Fires Usually Start

Most car fires begin in the engine compartment or around the running gear and wheel area, typically triggered by mechanical or electrical failures; passenger compartments are less common points of origin, and while crash-related fires are a small share of incidents, they account for a disproportionate number of fatalities. Analyses of U.S. incident data (e.g., from NFPA and the U.S. Fire Administration) consistently find that roughly three in five highway vehicle fires originate in the engine, running gear, or wheel areas.

The typical points of origin

Investigations show clear patterns in where fires start because heat, fuel, and electrical energy are concentrated in predictable parts of a vehicle. Understanding these hotspots helps drivers spot problems early and prioritize maintenance that reduces risk.

The following locations account for the majority of vehicle fire starts and the reasons they are vulnerable.

• Engine compartment: The most common origin due to hot surfaces (exhaust manifolds, turbochargers), fuel and oil lines, and dense wiring. Fluid leaks, failed hoses, and electrical shorts can ignite combustibles.
• Running gear and wheel area: Overheated brakes, seized wheel bearings, and dragging brake pads can ignite wheels/tires. Overheating catalytic converters can also ignite underbody debris.
• Underbody/exhaust system: Catalytic converters run extremely hot; contact with dry grass or roadway debris trapped near the exhaust can start fires beneath the vehicle.
• Passenger compartment/cargo area: Less common for accidental starts, but involved in arson, smoking-material ignitions, or faults in aftermarket electronics (e.g., audio, inverters, seat heaters).
• Battery and high-voltage systems (EVs/hybrids): Rare compared with all causes overall, but when they occur, thermal runaway events typically involve the traction battery pack (often under the floor) after damage, manufacturing defects, or charging-related faults; 12‑volt systems can still cause traditional electrical fires in any vehicle.

While all areas can be involved, the concentration of heat sources, flammable liquids, and electrical circuits makes the engine bay and wheel/undercarriage zones the primary origins in conventional crash-free fires.

Why those areas ignite

Fire needs heat, fuel, oxygen, and a source of ignition. Modern vehicles pack these elements into tight spaces, especially around the powertrain. The mechanisms below explain the most frequent ignition pathways.

Key mechanisms that turn faults into fires include the following.

• Fluid leaks onto hot parts: Engine oil, power steering fluid, transmission fluid, or fuel contacting exhaust components can ignite.
• Electrical faults: Chafed wiring, corroded connectors, or overfused circuits can arc and ignite insulation or nearby plastics. Aftermarket add-ons are a common factor when poorly installed.
• Overheating brakes/bearings: Dragging brakes or failing bearings create intense heat at the wheel, leading to tire or brake material ignition.
• Catalytic converter heat: Converters can exceed 1,000°F (538°C). If they are clogged or overloaded, temperatures rise further, igniting underbody debris or vegetation.
• Charging and battery issues (EVs/hybrids): Physical damage, internal defects, or thermal management failures can trigger thermal runaway in lithium-ion cells; high-voltage cables and connectors also carry ignition risk if compromised.
• Crash-induced leaks and shorts: Although a smaller share of all incidents, crashes can rupture fuel systems or crush wiring, producing fast-moving fires that are more likely to be fatal.

In short, heat buildup, combustible materials, and electrical energy converge in the engine and wheel areas, making them the likeliest origins when something goes wrong.

Warning signs drivers should not ignore

Early detection often prevents a fire. If you notice the following signs, act quickly and safely.

Watch for these indicators and respond promptly.

• Smell of burning plastic, rubber, or insulation from the engine or dashboard.
• Visible smoke from wheel wells or the hood, or steam that smells “sweet” (coolant) or “oily.”
• Warning lights (battery, temperature, check engine) plus dimming lights or electrical glitches.
• Unusual heat near the floorboard or center tunnel, or hot wheels after a short drive.
• Fluid leaks under the car, particularly fuel or oil near the exhaust.
• Burning or melting around charging ports or cables (for plug-in vehicles).

If any of these appear, stop in a safe place, turn off the engine, move away from the vehicle, and call emergency services. Do not open the hood if you see fire or heavy smoke—introducing oxygen can intensify flames.

How investigators pinpoint the origin

Fire origin is determined through systematic examination of burn patterns and damaged components. This matters for safety recalls, insurance, and prevention guidance.

Here are common tools and clues used during vehicle fire investigations.

• Burn patterns and “V” shapes that point back to the hottest and earliest area of involvement.
• Component autopsies of alternators, wiring harnesses, battery modules, fuel rails, and hoses.
• Melting and beading on copper conductors indicating arcing.
• Heat discoloration on exhaust parts near suspected leak points.
• Data logs from engine control units and, for EVs, battery management systems.

Together, these indicators help differentiate an electrical origin from a fluid-fueled fire or a heat-only event such as brake or converter overheating.

Prevention: practical steps that reduce risk

Most accidental vehicle fires are preventable with attentive maintenance and cautious operation. The following actions target the most common origins.

Adopt these practices to lower the odds of a fire.

• Fix leaks promptly: Address fuel, oil, and coolant leaks; replace brittle hoses and clamps.
• Protect wiring: Repair chafed looms, avoid overfusing circuits, and use proper routing and grommets.
• Be cautious with aftermarket installs: Use fused power feeds and professional-grade connectors; avoid tapping into critical harnesses.
• Maintain brakes and bearings: Service dragging brakes and noisy or hot wheel bearings immediately.
• Keep the underbody clear: Don’t park over dry grass; remove debris lodged near the exhaust or catalytic converter.
• Mind charging safety (EVs/PHEVs): Use certified equipment, ensure intact cables/connectors, and follow manufacturer guidance; seek inspection after any underbody or battery impact.
• Heed warning lights and smells: Don’t “drive through” electrical or overheating warnings.
• Carry a small extinguisher rated for Class B and C fires, but only use it if the fire is incipient and it’s safe to do so.

Regular inspections and careful modifications address the primary ignition scenarios in the engine bay and wheel/undercarriage areas, where most fires start.

Summary

Car fires usually start in the engine compartment or around the running gear and wheel area, where heat, fuel, and electrical systems converge. Mechanical failures (leaks, overheating brakes/bearings) and electrical faults are the dominant triggers; passenger-area starts are less common, and crash-related fires, though fewer, are more deadly. Prompt maintenance, cautious aftermarket wiring, and attention to early warning signs markedly reduce the risk.