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Why Is There Smoke Coming From Underneath My Car’s Hood?

Smoke billowing from the hood of your car is an unmistakable sign that something is definitely off. It could be a sign of a simple issue, or something is terribly wrong with your vehicle. It is normal to see a small white puff of smoke coming from your tailpipe after sitting overnight. It's just water vapor. On a rainy day, you may also notice some steam coming from the hood as water comes into contact with the exhaust or the radiator. However, if you are driving and suddenly smoke starts billowing from the engine or tailpipe, you need to stop immediately and take a peek.

Before you panic, it is important first to understand what the color or smell of the smoke implies. Identifying the cause will help you determine whether to keep driving or to reach out to a repair shop for their expertise.

What causes a car to smoke?

When small amounts of motor oil or other fluids spill or leak from a damaged seal or gasket onto the exhaust system or a hot engine, it causes the production of smoke under the hood of your car. Some of the leaking fluids may include power steering, engine coolant, transmission or brake fluid, or even window washer solvent.

What is the significance of different colors of smoke?

White smoke: White smoke could mean that the engine is having some trouble, a cracked cylinder head or engine block, a leaking head gasket, or a coolant is penetrating the combustion chamber. If the smoke smells sweet, then the coolant is very likely the cause of the smoke. If the smoke smells like fuel, then there is something wrong with the fuel system controls.

Blue or gray smoke: Blue or gray smoke accompanied by a bitter, pungent smell is a sign that the engine is burning oil. The most probable oil source could be worn piston rings, leaking valve seals, an overfilled crankcase, a plugged PCV valve, using the wrong type of oil, or failing to change the oil regularly. When a defective transmission vacuum modulator allows transmission fluid to leak into the intake manifold, thick gray smoke is produced.

Black smoke: Black smoke is a sign that your vehicle is burning too much raw fuel. When there is incomplete combustion due to a leaking fuel injector, a failed engine sensor/ ignition component, or a defective fuel pressure regulator, raw unburned fuel makes its way into the exhaust system and out through the tailpipe. This black smoke will smell of gasoline.

Another possible reason for black smoke is an electrical failure due to a short circuit. It will cause interference with other electrical devices and the lights to flicker.

What should you do when your car starts smoking?

You should pull over and determine if it is safe to keep on driving. Check the warning lights and gauges to determine if the engine is overheating. This will determine if you can drive to a repair shop or call a tow. Ensure a qualified technician thoroughly inspects your vehicle to determine the cause of the smoke. Consult our auto repair shop today for any engine repairs.

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