Car maintenance is a little bit timing when to bring your vehicle in for inspection, and a little bit noticing the signs your car makes when it’s warning you of potential problems.
One of the things you never want to see is smoke pouring from the exhaust, regardless of the color. This signifies a deeper, internal problem, and suggests something is wrong. In general, a cloud of thick white smoke indicates a major issue needs to be addressed quickly, or risk something as serious as a blown engine.
Understanding the exhaust system
Before we analyze what smoke coming from the exhaust pipe might mean, it’s important to understand what it is and where it comes from.
Essentially, your vehicle’s engine needs four things to work:
- A spark
Fuel is the basic lifeblood of keeping your vehicle working. Too much, and it runs rich. This can waste fuel, but can also eventually damage the engine. Too little, your engine will struggle, or not run at all.
Air mixes with the fuel, which causes it to flow either at the perfect level, or can cause it to run rich or lean. As the two mix, it combines with a spark to ignite the fuel and start the car. This needs to have the right timing to ensure the engine runs efficiently.
This timing affects how much emissions your engine emits. As your car ages, the process becomes less efficient. Older parts can mean each process is just a little off. That’s why older cars have less rigid emissions standards than newer cars.
What normal exhaust looks like
The exhaust pipe is there to pull emissions from the engine compartment and release it away from your vehicle. The gas coming from your tailpipe should be clear. On a cold day, the moisture in the emissions can sometimes look like a thin, white cloud.
That’s because gas moves through a process to clean it before it’s released into the air supply. The catalytic converter is an exhaust emissions control device that converts the toxic gasses produced by the engine, and transforms into less harmful pollutants by changing their chemical structure.
If you see something other than gas and air moving from the tailpipe, which has a clear visual appearance, you’ll notice it as smoke. A thick plume of white smoke from the exhaust comes from either water or coolant burning.
Water or coolant can sometimes leak, moving into the combustion chamber as your vehicle operates. It can move through cracks in the cylinder head or engine block, or if your vehicle is experiencing a blown head gasket. Any of these indicate a major repair.
White smoke is pouring out of the exhaust pipe … now what?
White smoke is a clear indicator of a bigger problem. The more you drive your vehicle, the more extensive damage may occur inside the engine compartment. Continuing to drive with a crack in the cylinder head, engine block, or coming from a blown head gasket could lead to further damage, contamination, or possible overheating. Drive too far under these conditions and you’ll have to replace the engine to get it operational again.
Another way to check where the problem originates is by checking the coolant level. If it’s low and you don’t see coolant leaking anywhere else in the engine compartment, it supports the theory that there is a leak in the engine block or head gasket. Once this is cracked or blown, replacement is the only way to repair.
Q&A – Common questions we get about white smoke from the exhaust
Q: Can low oil be the root cause of white smoke?
No. If oil somehow makes it into the combustion chamber, you’ll see a blueish smoke emitting from the tailpipe.
Q: What if the smoke looks black or gray instead of white?
Each color indicates a different problem. Black smoke can mean too much gas is burning, the air filter may need changing, or the fuel injectors may be clogged. Gray smoke is often caused by burning excess oil or a crankcase ventilation valve malfunction. With an automatic, gray smoke can also be a sign of a transmission fluid leak into the engine.
Blue smoke has a few causes. It could be motor oil burning in the fuel system, valve seals or piston rings breaking down. Cars with high mileage are also prone to emitting blue smoke. If you notice blue smoke, watch it for a bit. If motor oil is accidentally spilled onto the engine, it may look blue as it burns off. If it disappears right away, it’s probably nothing.
Q: What is in the exhaust that makes it so bad?
Exhaust gasses come from the combustion process inside the engine. As it operates, it produces carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen oxide, and hydrocarbons. Carbon monoxide is poisonous and needs to be directed away from the vehicle. The catalytic converter’s job is to convert it into carbon dioxide.
Q: What about bad spark plugs? Can they cause white smoke emissions?
No. Spark plugs are used in the ignition system, but they don’t cause white smoke. Spark plugs have their own symptoms if they’re going bad.
Q: What if smoke only appears when climbing a hill?
That can be common here along the Front Range, especially if you regularly pull heavy loads into the mountains. It’s almost always darker smoke, ranging from dark gray to black. The usual source of the problem is the carburetor. If the carburetor sends more excess fuel into the system when the engine is already stressed, it can create a puff of smoke. If this is the only time you see it, there’s nothing to worry about.
Q: What about electric cars? Would the same problem exist with electric?
Exhaust gasses are produced with combustion engines. Because electric vehicles run on a battery, it won’t produce exhaust. In fact, electric cars won’t have a tailpipe on their design.
Do you have white smoke coming out of the exhaust?
If so, it’s time to bring your vehicle in for servicing. Different shades of color will mean different things. But if you continue to see smoke of any color, it’s an alert that something is wrong.
To reduce higher repair bills, coming in sooner will catch the problem early, and hopefully prevent it from escalating over time.
What questions can we help you answer about the exhaust system?