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White smoke from exhaust on startup then goes away may happen due to the usual condensation buildup. It is only problematic if the smoke persists due to a valve seal leak, clogged fuel filter, or other problems.
Stay with us throughout this article to find other reasons and fix the smoke coming out of your car.
JUMP TO TOPIC
- 1 Why Does White Smoke Come From the Exhaust on Startup Then Goes Away?
- 1.1 Condensation on Cylinder Walls or Exhaust
- 1.2 High Fuel/Air Mixture in the Engine
- 1.3 Smoke Due to Cracked Cylinder Head
- 1.4 Problems Due to Broken Piston Rings
- 1.5 White Smoke Due to Broken Valve Stem Seals
- 1.6 White Smoke Due To Faulty Fuel Injectors
- 1.7 False Injector Pump Timing
- 1.8 Smoke From Coolant Leakage
- 2 How To Fix a Car That Emits White Smoke From Exhaust During Startup?
- 3 Why Does White Smoke Come From the Exhaust When the Engine is Hot?
- 4 Conclusion
Why Does White Smoke Come From the Exhaust on Startup Then Goes Away?
White smoke comes from the exhaust on startup then goes away because of normal winter season condensation or rich air-fuel mixture. It can also happen due to broken piston rings, injector seals, or a cylinder head. You can also suspect a faulty injector, fuel injection timing, or coolant leaks.
Condensation on Cylinder Walls or Exhaust
A car blowing white smoke but not overheating might have moisture on the cylinder walls or exhaust. A little condensation over the cylinder walls is common in some circumstances, mainly during the winter season. These moisture droplets mix with exhaust pollutants and appear whiteish.
The condensed particles evaporate when the gas engine warms up, but frequent condensation may signal a problem. Some issues include coolant discharge in the combustion zone, a damaged head gasket, or a fault with the cooling system.
You should first know how much white smoke from exhaust is normal. If the smoke only appears when you start the car and disappears later, it’s normal. If you notice unusual condensation or white smoke, get the vehicle evaluated by a trained technician. They will detect and repair any underlying problems.
High Fuel/Air Mixture in the Engine
Another reason for white smoke out of exhaust on startup is the engine control unit (ECU) signaling for a rich fuel mixture. This helpful feature in most modern-day cars quickly warms up a cold engine. Fuel must be mixed into the right quantity of purified air through the air filter.
The smoke arises because the excess fuel fails to burn in the combustion chamber when the fuel-air ratio changes. It produces vapors that condense in the exhaust pipe and appear from the tailpipe.
Moreover, the engine revs higher when you push the accelerator. The fuel and air quantity available for the engine rises, resulting in enhanced combustion and power output. Consequently, the engine speed and RPM both increase.
Smoke Due to Cracked Cylinder Head
If you are still thinking, “Why does smoke come out of my exhaust when I start it?” you can check the cylinder head. The cylinder or engine head covers the burning chamber and links to the engine block. It has channels that connect to the block channels and transfers oil or coolant.
The engine head accommodates vital parts, such as exhaust manifolds, spark plugs, and injectors. It is made of aluminum and bears great pressure and stress as the engine runs. As a result, it may bend or crack.
A smashed engine head means that the oil and coolant can leak. The fluids seep into the burning chamber, and white smoke emits from the exhaust. Unlike the causes mentioned above, the smoke production, in this case, does not stop when the engine gets hot.
You can detect the smoke due to a broken engine head if you experience a loss of power or overheating.
The engine head may break due to one of the following reasons:
- Overheating expands, warps, and cracks the engine head. The engine may overheat due to a damaged thermostat or coolant discharge
- Abrupt temperature changes, for example, quick engine warm-up in freezing temperatures
- Mechanical stress due to heavy load, bad engine tuning, or vibrations
- Premature ignition in the burning chamber
Problems Due to Broken Piston Rings
A piston ring fits inside the cylinder closing the void between the cylinder wall and the piston. Different types of rings have distinct features, and all of them are necessary for proper engine operations. If the rings break, you will see blue, white, or grey smoke from exhaust on startup.
Compression rings, as the name suggests, maintain the pressure inside the burning chamber. The scraping ring returns the lubricant from the walls to the crankcase, and the oil control rings lubricate the walls.
If any of these rings fail to seal, a plethora of problems may arise.
- Rough idling and decreased fuel efficiency
- Poor engine performance due to loss of compression
- High oil consumption as it seeps into the burning chamber
- High friction and engine damage because of poor cylinder walls lubrication
- Blue smoke from the exhaust, but if excess oil burns, you will see white smoke coming out
White Smoke Due to Broken Valve Stem Seals
Valve stem seals form a seal within the valve guide and valve stem, keeping oil out of the burning chamber and the valve running smoothly. They maintain appropriate valve stem lubrication while reducing excessive usage of oil. Moreover, they prevent oil from entering the burning chamber. These seals may break, leading to the production of white smoke because the oil starts to burn with the fuel.
The following factors can lead to breakage of valve seals:
- Seal breaks over time as it undergoes pressure and stress. It also heats and cools repetitively, which can lead to hardening, so the seal becomes prone to cracking.
- Loss of flexibility because the seal is in close vicinity to the combustion process. The process generates considerable heat that hardens the seal and leads to cracks and oil leakage.
- Oil contamination due to dirt or carbon deposits speeds up the wearing of the seal. As a result, the seals become brittle when they come in contact with the polluted oil.
- Avoiding regular maintenance or using poor-quality engine oil increases the chances of seal wear. Regular oil change prevents dirt buildup and saves the seal from premature wear.
- Making changes to the engine for improved performance, such as changing the valve timing, puts extra stress on the seal.
White Smoke Due To Faulty Fuel Injectors
The white smoke from exhaust after sitting idle a few minutes can be associated with a bad fuel injector. The injector controls the fuel supply, but a fault can lead to the production of smoke.
You will also encounter rough idling, poor performance, and greater fuel consumption. All these issues, along with hydrocarbon emissions, help detect incorrect injectors. The color of the smoke varies depending on the injector damage. For example, if you see black smoke, the injector must be injecting a high volume of fuel into the chamber.
It happens when the injector loses control and remains open for a long time. The black gas discharge indicates that the extra fuel did not burn, so the exhaust expelled hydrocarbons. An oil discharge through the injector results in blueish smoke. It happens because the oil accumulates in the combustion engine, and when you start the car, the oil starts burning along with the fuel.
On the contrary, white smoke appears if there is a coolant or water leakage. It is not very common, but there is still a possibility if you face the white smoke problem. Damaged injector sealing or a fault in the cooling system allows coolant into the burning chamber, where it mixes with the fuel.
False Injector Pump Timing
False injector timing can also lead to white exhaust emissions. The injector timing goes off for various reasons, such as a glitch in the ECU. Other mechanical injuries to car components, such as the fuel pump (in the case of diesel engines) or camshaft sensor alter the timing. You can also check the electrical connections around the ECU and injectors. A damaged wire or connector can fail to pass the signal to the injector, resulting in false timing.
Contamination of the fuel can gradually impact the operation of injectors. In some cases, poor-quality fuel also alters the injector timing, and the exhaust emits white smoke.
It is only the tip of the iceberg because false injector timing causes big issues such as engine knocking. If left unchecked, it can damage the cylinder walls, pistons, valves, engine block, and other parts.
Smoke From Coolant Leakage
If you see the exhaust smoke and observe a sweet smell, there might be a coolant discharge into the combustion unit. Coolant that seeps into the combustion chamber combines with the fuel-air mix. As this occurs, the coolant vaporizes and is discharged as white smoke via the car exhaust system.
A blown head gasket is a typical source of coolant loss. The gasket closes the combustion chambers by sitting between the motor block and the engine head. Therefore, if the gasket breaks, coolant can seep into the chamber, causing white smoke.
Coolant can also seep into the chamber if the engine head is damaged. It can occur as a result of overheating. When the coolant reaches the burning chamber, it burns alongside the fuel, producing white smoke.
The intake manifold gasket also handles sealing the inlet chamber to the motor’s block. Coolant can seep into the manifold and, eventually, into the burning chamber if the gasket breaks.
You can also consider other parts of the cooling system, such as the radiator, water pump, or hose. White smoke can emit from the exhaust pipe if any of these components fail. The white exhaust smoke petrol-powered engine problem is quite common.
How To Fix a Car That Emits White Smoke From Exhaust During Startup?
You can fix a car that emits white smoke from exhaust during startup by filling the coolant in the reservoir and repairing the leakage points. You can also replace the broken intake or head gasket or weld the engine head. Cleaning the fuel injector can also fix the problem.
Fix the Low Coolant Level Problem
If you doubt a coolant leakage or the car releases a sweet smell while emitting smoke, you should start by filling the coolant. It is a simple procedure and costs less than other repair methods mentioned here. Park your car on an even surface, wait for the engine to cool down, and open the hood to locate the coolant tank. If it is your first time, you can consult your car’s manual to locate it.
The reservoir always has markings such as “full” and “low.” If the coolant level lies below the “low” mark, you can fill the tank with coolant up to the “full” mark. Always buy a good quality coolant because it has long-term impacts on the engine.
Filling the coolant is not enough when you have a leaking component, so you should diagnose the root cause. Mostly, a cooling pressure test helps pinpoint the leakage spot. The most common internal coolant leakage points are cracks in the engine head, head gasket, or motor block.
Repair the Leakage Point To Stop Smoke Production
It is crucial to find the point of leakage, otherwise, there is no use filling the coolant reservoir tank. An intake manifold gasket can cost from $200 to $550 to replace. The gasket alone is inexpensive, with prices ranging from $20 to $120. The labor is expensive, ranging between $170 and $420.
Repairing a head gasket can cost thousands of dollars, so it is generally quicker and less expensive to discard the affected part and replace it. A head gasket replacement costs around $1,600 to $2,000. The parts alone cost from $700 to $900, while labor costs between $900 and $1,200.
If the leakage is because of a crack in the cylinder head, you can repair or replace it. If the engine head is made of cast iron, you can weld it. Depending on the car model and labor cost, you might have to spend somewhere between $500 to $1,000.
If it is beyond repair, you will have to replace it. The labor cost is higher in this case because removing the engine head and then replacing it can be a tough job. Also, in some cars, the engine heads are easily accessible, while they are hard to access in others.
You can get the cylinder head replaced for $2,500 to $3,500. The labor cost alone is $1,200 to $2,800, and the components are comparatively inexpensive at around $200 to $500.
You can also repair or replace a cracked engine block. A mechanic can mend it with a cold-metal patch or weld it shut. These processes can be expensive and take up to 35 hours to fix, depending on the car model.
The total cost can be around $2,500 to $4,000, which makes it more expensive than replacing the engine block. So you can choose between a replacement costing $600 to $2,500 or repair the block. The labor cost varies on the per-hour charges of the shop, but usually, it is around $90 to $150 per hour.
Replace or Clean the Clogged Fuel Injector
If you are thinking about how to fix white smoke from exhaust on startup if there is a problem with the injectors, you have two options. You can clean the injector or replace it.
Cleaning is quite simple because injector cleaning agents are easily available at stores. You can do your research and buy from a reputable brand. Make sure you buy a cleaner that works for your car and then follow the instructions that come with the cleaner.
You can buy a cleaning agent for $5 to $30, depending on the brand and type. Some cleaners are in the form of additives, while others are pour-in treatments. If cleaning does not fix the problem you will have to replace the injector, but remember that you should replace all injectors. If you only replace the faulty injector, your car’s petrol engine might not work smoothly.
Why Does White Smoke Come From the Exhaust When the Engine is Hot?
Now you know all the reasons behind the white smoke that comes from the exhaust on startup before going away instantly or persisting. It will help you understand when your car needs repair.
Keep the following points in mind if you are facing a similar issue:
- Smoke due to condensation or a high air-fuel mixture is fine if it goes away after a few minutes.
- You need to check for a blown head gasket, cylinder cover, or engine block if the smoke persists.
- You can fix the car by fixing the leakage point, filling the coolant, or cleaning the injector.
Start noticing the smoke timing to diagnose the problem and hire a mechanic for more difficult solutions.
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