a white smoke from exhaust on startup
Tips & Tricks

6 Reasons for White Smoke from Exhaust on Startup

Smoke from your car’s exhaust should be colorless. Colored smoke may indicate an underlying problem with various components of your engine. Such malfunctions could cost you a pretty penny in terms of repairs or replacements. So why is there white smoke from exhaust on startup? Let’s find out.

Exhaust Emissions

Exhaust emissions occur when an air-fuel mixture burns inside internal combustion engines. Emissions from this reaction usually contain a combination of the remnants of atmospheric air, water vapor, carbon dioxide, and other components in a gaseous state. These vary from black, to blue, and white, the most common color from exhaust emissions.

Diagnosing a Smokey Exhaust

Diagnosing a smoky exhaust is the first step to finding a suitable solution for your car’s engine.

It is important to observe:

The time it appears (whether it only appears when stationary, during start-up, or when the engine is running)

  • The color and kind of smoke
  • The smell of the smoke
  • The time the smoke appears

Smoke might appear when your car is stationary, accelerating, or when the engine is running. Smoke caused by water or antifreeze entering the cylinder might be no cause for alarm. It is, however, important to confirm whether you have the correct amount of antifreeze in the radiator and overflow bottle.

Smoke during startup could result from condensation, which is nothing to worry about if it clears after a few minutes of driving.

The Color of Smoke

While smoke coming from your exhaust could cause alarm, the color of the smoke could pinpoint the underlying issue your car has.

Thin white smoke on a cold morning is nothing to be concerned about. Thick smoke could indicate that your engine might be burning fuel containing coolant, which means that your radiator might be leaking.

Blue smoke that appears when your engine lights up in the morning might indicate that your engine is burning oil. This also means that you need to see your mechanic immediately.

Gray exhaust smoke is usually caused by burning the transmission fluid.

Black smoke points out that your engine is burning too much fuel and shows that your engine is not being cared for properly. It might also indicate that you need to change your air filter.

What’s That Smell?

Since the car exhaust port functions to neutralize the harmful fumes that emanate from the engine, foul smells from the exhaust indicate that there is a problem.

The smell of rotten eggs comes from small amounts of sulfur present in the fuel. It may also indicate the need to replace the converter and the fuel filter.

A strong exhaust smell may indicate a leak into the exhaust system, while a constant sweet scent indicates that the antifreeze is leaking.

Why is there White Smoke from Exhaust on Startup

white smoking popping out of the car

Here are several reasons why white smoke appears from your car’s exhaust upon startup.

Condensation Build Up

In cold temperatures, you may notice a thin veil of white smoke, no cause for alarm. This occurs when the warm exhaust gases meet with the cold air, which results in condensation and steam.

This usually requires that the car is warmed up thoroughly. Once the engine starts to warm up, mainly after 30 seconds to 1 minute, the smoke should diminish.

Coolant Leak

If, after 1 minute of warming up your engine, the smoke is not disappearing, you might want to check your engine for a coolant leak. This could be because your car has a cracked cylinder head or a leakage from the head gasket, or a cracked engine block.

Cracked Cylinder Head

The most common reason for a cylinder head crack is usually overheating, which is caused by the rapid heating of the engine or other stressful functioning conditions.

This crack allows the coolant to leak out of it and mix with the engine oil, and the coolant then contaminates the engine oil once mixed. The fumes released will be thick and white with a consistent sweet odor that doesn’t disappear during combustion.

Head Gasket Failure

You can find the head gasket between the cylinder head and the engine block. It is a thin metal sheet that is vital as it seals the internal combustion process to allow the coolant and the oil to travel throughout the engine to cool and lubricate.

Cracks form in the gasket for many reasons, but wear and tear are most common. When this crack happens, the coolant seeps from the cooling channels of the engine into the cylinder, where it gets burned, producing thick white smoke. The only way to fix this is to replace the gasket.

Cracked Engine Block

A cracked engine block is the most severe issue in the automotive repair field as it means replacing your engine altogether in the worst-case scenario. It is ambiguous to determine since, in most cases, it can be mistaken for other issues such as a cracked cylinder head or a blown gasket. This is because it can present similar symptoms like Steam from the exhaust pipe, coolant or oil leaks, and engine overheating, among others.

Engines are made of either cast iron or aluminum alloy to ensure their durability and that they can last through dynamic heat conditions. When the engine overheats, the block can crack due to thermal stress.

The crack can also occur in freezing temperatures if the cooling system has more water than required and insufficient amounts of antifreeze. This happens when water freezes and expands, which stresses the walls and causes them to crack.

Fuel Injection Malfunctions

Faulty Fuel Injector

A fuel injector is an essential component in charge of sending fuel into the internal combustion chamber. It functions to deliver fuel at the right moment, pressure, and amounts. At its peak performance, the fuel injector plays a considerable role in ensuring excellent fuel economy, high engine power, and a smooth ride.

A slight change in the pressure or timing can throw the whole system out of balance. If the injector malfunctions, there will be a delay in receiving the fuel, and the amount of it will be off. An excess of fuel means that the engine will need to combust and expel, resulting in the thick white smoke.

Clogged fuel injectors do not let fuel through them, leading to a loss of power in your engine. This will require you to seek professional cleaning or acquire a complete injector replacement.

Leaking fuel injectors can lead to pricey damages if left unaddressed. A leaking injector obstructs proper injection and combustion processes. Once the fuel seeps, it will pollute other engine components resulting in breakdowns.

Injector Pump Timing for Diesel Engines

Since combustion is a delicate process, the timing of the pump is important as it highly contributes to the efficiency and power of the engine. This is because the diesel has to be pushed into the cylinder moments before the end of the compression stroke.

A fault in the timing of the fuel injector means that the cylinder is affected. This leads to a diesel overrun, resulting in a thick white smoke coming out of the tailpipe.

It is advisable that once you have discovered this fault with your injection pump, seek the help of a professional as this requires an excellent level of skill.

Oil Level Variations

When the engine contains more fuel than it should hold, your car will emit white smoke with a blue or grey tint. This is because the excess oil results in a buildup of oil in the combustion chamber.

Steps to Fix White Smoke from Exhaust Startup

While the underlying issues that cause your engine to emit white smoke could range from normal to severe, it is important to fix the exhaust problem urgently.

This will ensure that the issue does not affect other parts of your car and saves you time and money.

Check the Coolant Level

If the coolant level is low and you do not find any indication of it leaking from the coolant reservoir tank, the chances are that there is a leak due to a crack in the head gasket.

Inspect the Intake Gasket for Cracks

The engine overheats if the gasket develops a crack, giving you the white flames. To remedy this situation, you should replace the cylinder immediately.

Examine the Head Gasket

The head gasket functions as a seal that inhibits the coolant from getting into the cylinder. If you find a crack on inspection, change the gasket right away.

Cracks in the Cylinder Head

Repairing a cracked head cylinder is highly dependent on the material it is made from.

For cast irons, you can repair the cylinder head by welding. If it is beyond repair, the entire cylinder-head should be replaced.

Inspect for Cracks in the Engine Block

Repairing such cracks require the work of a professional and is costly. You can fix these cracks by re-welding them, cold-metal stitching them shut, or using a cold-metal patch over the crack.

Clean or Replace the Fuel Injector

Fuel injectors are inclined to get clogged by carbon deposits and sludge formation. They can be cleaned using commercial fuel injector cleaners or replaced altogether.

Inspect Valve Seals or Piston Rings

You should replace these parts once they begin to fail since they are predisposed to wear and tear.

Replace Diesel Engine Fuel Pumps

If you discover that the issue lies in the timing of the injector pump, the solution would be to reprogram the computer. If this approach fails, you will need to replace the entire pump.


There is a need for all car owners to constantly check the condition of their car to ensure that the slightest issues are resolved early and at a lesser cost.

Subtle signs like the color of your exhaust fumes will help you determine the health of your car so that you can maintain it and ensure the longevity of your vehicle.

A cloud of thick white smoke is an indicator of severe engine malfunction. You need to handle such cases urgently to ensure the problem does not spread to other components of your car.