White Smoke From Exhaust: Main Causes and How to Fix

You never want to see smoke coming out of your car’s tailpipe. In most cases, some thin white smoke from your exhaust in the winter is perfectly normal and not a source of concerns. However, whenever you notice thick bursts of white smoke from exhaust, it is a sign that something is wrong with various components of your engine, whether it’s white smoke from exhaust on startup or white smoke from exhaust when accelerating.

The most common reasons for thick white smoke from exhaust involves some malfunction that requires immediate repairs or replacement of faulty parts, many of which are very expensive, and if you continue to drive in this state, you would risk further serious and expensive damage to your engine. To avoid this, you must understand the various root causes of white smoke from exhaust and master the maintenance steps of how to troubleshoot and fix these problems. Also included is the cost for repair or replacement in each case.

Exhaust Emissions: What’s Normal?

Before we go on to explain why thick white smoke from exhaust is a sign of troubles, you must first understand where exhaust fumes come from and what is normal. Inside your engine’s combustion chamber, a spark ignites the mixture of fuel and air, creating a series of combustions or contained explosions inside the cylinder. The direct byproducts of such explosions are exhaust gases that get funneled down the exhaust system. Before exiting through your tailpipe, these gasses pass through the muffler to reduce noise and through a catalytic converter to reduce harmful emissions. 

Under normal conditions, you shouldn’t be able to see the exhaust coming out of your tailpipe. Especially in winter though, you might occasionally see a thin veil of smoke that is white in color, which is just water vapor. This is perfectly normal and would disappear after a short while. It’s important to understand that while thin white smoke from exhaust is normal, if it is thick and comes out in visible bursts, you will need to perform inspection of various parts to diagnose the source of the problem.

What Does White Smoke From Exhaust Mean? 

white smoke from exhaust
Thick bursts of white smoke from exhaust means problem with your engine components. Source: GoMechanic

Thick white smoke from exhaust suggests that coolant or water has inadvertently entered the combustion chamber, which they should never. When coolant or water is burned within the engine block, it produces thick white smoke that exits through your tailpipe. 

A common occurrence is white smoke from exhaust emitted in thick bursts. Never ignore this and let it prolong. The most common reasons for this occurrence include cracks to vital engine parts, including damages in the cylinder head, head gasket or engine blocks. Even if it’s only a small crack, the damage can easily become more extensive if you continue to drive and postpone replacing the cracked component. It could result in further contamination of engine oil or engine overheating, which can lead to permanent engine damage. You’d then have to replace the completely broken down engine, which is expensive and is a job best left to the professionals. 

What does white smoke from exhaust mean? Below are the 9 most common reasons for white smoke from exhaust, and further below is how to troubleshoot and deal with each culprit. 

Reasons For White Smoke From Exhaust

Thin White Smoke: Condensation Buildup

Thin white smoke on startup then disappears is usually a result of condensation build-up within the exhaust system. It tends to occur in the winter or cold mornings. The smoke should be thin, not too visible and only be coming out in small amounts upon startup, and will burn out fairly quickly after your engine warms up, particularly after about 30 seconds to a minute. It is not a sign of trouble, but if it occurs in conjunction with other occurrences of reduced engine performance or difficult starting, it may indicate a more serious issue within your engine.

Coolant Leak: Damaged Coolant Reservoir Tank

Sometimes, if the coolant reservoir tank is damaged or cracked, it can leak coolant into the engine’s combustion chamber. This leaking coolant is then burned within the cylinders, creating thick white smoke from exhaust.

Coolant leak from a cracked coolant reservoir tank is generally less than the sources of leaks right below, but it can happen when you are fixing another problem nearby and accidentally damage the tank. In any case, you’ll need to replace the damaged reservoir tank.

Coolant Leak: Crack in the Cylinder Head, Engine Block or Head Gasket

While a cracked coolant reservoir tank is rare, when most mechanics hear about thick white smoke from exhaust, they would assume the worst. That is usually due to a crack in the cylinder head, head gasket or engine block, all of which are not very quick and cheap to replace, and is not a maintenance job for the novice. 

Cracks in these parts are caused by a consistently overheating engine due to low coolant levels, which is due to leaking coolant, and constant temperature fluctuations of the engine. They allow coolant or oil to leak into the cylinders, which then are burned and produce thick white smoke from exhaust.

Cracked Cylinder Head

Whenever your cylinder head is cracked or damaged in any way, coolant will leak out of it and get mixed in with the engine oil. Once that happens, the oil will become contaminated. This doesn’t need to be a big crack; all it takes is a tiny crack to create thick bursts of white smoke from your tailpipe. As coolant continues to mix in with engine oil, the white smoke will begin to have a distinct sweet odor that won’t go away.

Cracked Head Gasket

cracked head gasket
A cracked head gasket must be replaced. Source: BlueDevil-Products

The head gasket is a thin metal sheet found between the cylinder head and block, sandwiching the top and bottom part of most engines. Its main function is to form a seal between the two parts and helps to prevent coolant leaks from the cover surrounding the engine. 

One of the reasons for cracks to form on the head gasket is just normal wear and tear. When this happens, the coolant is no longer contained within the cooling channels of the engine but finds its way into the cylinder, where it gets burned. A cracked head gasket cannot be repaired; it will need to be replaced right away.

Cracked Engine Block

The worst case scenario is that your entire engine block has a crack in it. If this is indeed the culprit, be prepared for an expensive and time-consuming replacement. You’d most likely require professional service in this case. 

Most engine blocks are made out of either cast-iron or aluminum alloy, so that they would last long in constant high-heat conditions and can also effectively transfer heat away from the engine. However, the engine is a complex system that requires each and every component to work in absolute precision. If any of the engine components isn’t working as it should, the block can overheat, which weakens and deteriorates it.

In addition to white smoke coming from the exhaust, there are few common symptoms that the block may be getting too hot, including discolored coolant, puddles of fluid under your car, frozen coolant in the radiator and poor performance since the engine can’t maintain proper compression if there’s a leak in the combustion chamber.

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Problems with Fuel Injection

Bad Fuel Injector

A fuel injector is basically a spray nozzle that delivers fuel to the combustion chamber as input for the combustions. Contrary to what many folks expect, the injector doesn’t control when or how much fuel gets sent, it just “injects”, that is it only acts to restrict or allow its passage at the right time. For optimal combustion within the engine’s chamber, it must inject fuel at precise moments, meaning even the smallest variation can throw the system out of balance.

If the fuel injector is leaking or is stuck in the open position or malfunctions in any way, then the chamber is no longer receiving the right amount of fuel at the right time. When there’s too much fuel in the engine that needs to burn off and be expelled, the result is thick white smoke from exhaust, which is sometimes tinted gray. It’s also possible that your fuel injectors are clogged, which render them effectively useless.

It’s not advisable to inspect the injection or try to change it on your own, as it is a job best left up to the mechanics. The reason that fuel injectors fail is mostly due to contaminants in the fuel. One way to avoid this is to replace the fuel filter routinely, at least every 2 years or so. 

Diesel Engines Only: Injector Pump Timing Is Off 

If your engine runs on diesel, the reason for white smoke from tailpipe is most likely an issue with the injector pump timing. The pump is in charge of injecting diesel into the cylinders. Like with the fuel injector in a gas-powered engine, if the pump’s timing is off and diesel is not delivered to the engine’s chamber at the precise moments, it can lead to an overrun of diesel, causing thick white smoke coming out of tailpipe.

Other signs of injector pump failure include trouble starting, poor idle, reduced performance, rough rides, reduced RPM limit and poor fuel economy. 

Engine Control Unit Error

Alternatively, there’s nothing wrong with the fuel injector, but you might have a faulty or simply glitchy engine control unit that is throwing off the timing of the fuel injector. This just means you need to reset or repair the engine control unit so that it can correct the timing of the fuel pump injector.

Often, to reprogram the computer, you just need to unplug your car battery for a few minutes. In the case that this does not resolve the issue of thick white smoke from exhaust, it’s best that you take your car to a certified mechanic who is familiar with the engine of your vehicle’s make and model.

Note: Blue-tinted White Smoke Due To Oil Leak

Sometimes the white smoke coming from exhaust is tinted blue, although many folks might not be able to distinguish this. Blue-tinted white smoke suggests that your engine is burning oil. 

The only thing that should be inside a combustion chamber is the precise mixture of air and fuel. If oil somehow finds its way into the cylinder, it will be ignited together with the air and fuel mixture, resulting in a thick blue-ish cloud of smoke to exit the tailpipe, which might appear to be white smoke to some people. Other signs include engine misfires and increased oil consumption. 

How can oil leak into the combustion chamber? This is most likely due to leaky piston rings or valve seals, allowing oil to flow inside. When oil is leaking, the engine components are not being lubricated properly by the oil, which means they’ll start to get worn out prematurely. This will cause a whole other flock of expensive repairs and replacement that no car owner would want to deal with.

In most cases, you shouldn’t have to deal with leaky piston rings or valve seals until after the 100,000-mile mark. One way to help prolong their lifespan is to switch to high-mileage motor oil.

How to Troubleshoot and Fix White Smoke From Exhaust

Check Coolant Level

If you want further proof that you’re having an issue with coolant making its way into your engine block when it should be contained, first, you should check the coolant level. If you notice the level is low and do not see coolant leaking from the coolant reservoir tank, it supports the theory that the leak is due to a crack in the head gasket, cylinder head or engine block. Furthermore, it’s advisable that you invest in an engine block leak detector kit that uses chemistry to detect whether your coolant is contaminated.

The first step is to open the hood. However, don’t forget that the engine should be sufficiently cool before you remove the radiator cap or reservoir cap. If the engine is hot, give it at least an hour or the longer the better to cool down before you attempt to check the coolant. 

Then, with your vehicle parked on a flat surface, open the coolant reservoir and look into the coolant chamber to check the coolant level. Look for the markings on the side of the plastic overflow bottle that say “Low” and “Full,” or similar terms, then grab a funnel and fill the reservoir until the level reaches “Full”. One way is to put a stick into its reservoir and check how much coolant there is. 

If the amount of coolant is adequate, proceed to inspect the other engine components below any cracks or any damage that may lead to the coolant getting mixed with engine oil or fuel. It’s advisable that you also perform a cooling system pressure check to try to determine which part is actually causing the leak (Pressure is applied to the system up to the range specified on the radiator cap. If the system cannot hold pressure for at least two minutes, then there’s a leak. If no external leaks are found, the highest possibility is a crack in the head gasket, cylinder head or engine block).

Step 1: Look For Any Crack In The Intake Manifold Gasket

The first thing to check, you would think, is the head gasket, but before this, you should inspect the intake manifold gasket first. The intake gasket seals the intake manifold; it not only transports coolant to the engine but also oxygen. If the intake gasket develops a crack, the engine overheats due to leaking coolant, air, and gas. Keep in mind that the gasket is mostly made of rubber or plastic. Therefore it is prone to damage caused by extreme heat. Fortunately, although it can get cracked or damaged, it can easily be repaired if detected early.

The replacement cost of an intake manifold gasket is anywhere from $190 to $540. The gasket itself is relatively cheap and will cost somewhere in the neighborhood of $20 to $120. What’s expensive is the cost of labor, which will be anywhere from $170 to $420, since replacing any engine component is not a straightforward job. 

Step 2: Look For Any Crack In The Head Gasket

After checking the intake manifold gasket, you should move on to the head gasket. The head gasket is designed to seal the head to the block in order to prevent the coolant from getting to the cylinder. If there’s a crack in the head gasket, it needs to be replaced immediately. 

The cost of head gasket repairs can run into the thousands, meaning it’s often easier and cheaper to just scrap the damaged part and replace it. It costs between $1,600 and $2,000 to replace a head gasket. The cost for the parts themselves vary between $720 and $850, while the labor costs range from $900 to $1,200.

Step 3: Look For Any Crack In The Cylinder Head

The cylinder head is essential since it connects to the engine block and head gasket. Due to the fact that it’s made of aluminum, it’s prone to warping or breaking in the case of engine overheating, releasing white smoke from exhaust. If upon inspection, you spot a crack, replace the cylinder head right away.

Repairing a cracked cylinder head will run between $500-$1,000 depending on whether it’s aluminum or cast-iron. Cracks in cast iron heads can often be repaired by furnace welding or flame spray welding. 

If the crack cannot be repaired, the entire cylinder head needs to be replaced. While it’s not all that hard of a job, it is an extremely time-consuming job because the engine head has to be removed and then replaced, thus the large portion of the replacement cost is labour cost. Also, labor costs vary greatly depending on the make and model of your vehicle. Luxury vehicles like BMWs, and Audis often have various components that need to be removed to get to the cylinder heads.

The average cost for cylinder head replacement is between $2,800 and $3,200. Labor costs are estimated between $1,200 and $2,700 while parts cost only anywhere from $200 to $500. 

Step 4: Look For Any Crack In The Engine Block

There are three possible methods for repairing a cracked engine block, that is using a cold-metal patch over the crack, cold-metal stitching it shut, or re-welding the crack. These require the work of a professional. Regardless of which route you opt for, it is certainly not cheap. The labor for an engine block repair could be anywhere from 12 to 35 hours, depending on the make and model of your vehicle, as for some models it’s much harder to get to the engine block and disassemble it. This can set you off between $2,500-$4,000 for a temporary fix.

In the case that it’s more sensible to salvage your current engine and get an engine block replacement, you can expect to pay between $600 and $1,000 for small block engines or between $1,550 and $2,500 for a long block engine, depending on the model being swapped. That’s only for the parts and machine costs. As for labour cost, the hourly rate can vary greatly, from $90 per hour to over $150 per hour. So the labour cost alone for a typical engine block replacement can run anywhere from $1,000 to $2,000.

Step 5: Clear or Replace the Fuel Injector

It’s also possible that your fuel injectors are clogged and cannot do their job properly. They are generally susceptible to getting clogged by carbon deposits and sludge formation. The good news is that there are commercial fuel injector cleaners that can help clear a dirty fuel injector.

Otherwise, if the fuel injector fails not because of clogs, this means it has reached the end of its life, so the only thing you can do is replace it. However, an important note is that you should always replace the entire set of fuel injectors rather than just replacing the problematic one, or else the engine won’t run evenly.

Step 6: Inspect valve seals or piston rings

Piston rings and valve seals are prone to wear and tear. If these fail, replacement is in order. Unfortunately, as simple as the parts might sound, replacing piston rings is extremely expensive, usually ranging from $1,800 to $3,500, of which the parts only run about $75-$200 and the remaining is for labour, since this is an extremely time-consuming job. 

Replacing valve seals costs a little less, but it still can cost you from $900 to as high as $2,000. Similar to piston rings replacement, the process of replacing valve seals involves disassembling the entire engine until you can reach the valve spring.

This means that unless you fancy yourself a self-taught DIY mechanic and are very knowledgeable about dismantling an entire engine, it’s recommended that you leave this to the pros.

Diesel Engines Only: Replace the Fuel Pump 

If the culprit of white smoke from exhaust is because the timing of the injector pump is off, you might simply need to reprogram the computer. If that doesn’t solve the issue, you will most likely have to replace the pump entirely. The average cost for a fuel pump replacement is between $220 and $1,100 depending on vehicle. Labor costs range from $120 and $260, while parts cost around $90 to $860.

The other possibility is that you have to replace the camshaft, which can run between $1,500-$3,000. These jobs are not suitable for the novice, as it requires tools and knowledge that only a certified mechanic would have.

And after you have the replacement performed, try to avoid fuel injector pump failure due to contaminants in the diesel. Remember to routinely replace the diesel fuel filter, as well as buying the highest quality of diesel you can afford at prestigious refill stations. 

White Smoke From Exhaust: Different Reasons for Diesel Engine and Gas Engine

When you encounter white smoke from exhaust, it’s important to note that this means different sources of problems in gas- and diesel-powered engines.  

When you encounter white smoke in your diesel-powered car, it means the fuel is not burning correctly due to a lack of heat in the combustion chamber. The unburnt diesel does not only cause white smoke but also contains certain toxins that will likely sting your eyes.

If you own a diesel-powered vehicle, in addition to the reasons discussed above, white smoke from exhaust is usually caused by low cylinder compression, low fuel pressure to the fuel pump, damaged fuel lines, incorrect or broken fuel pump timing, broken injection timing, cracked or damaged rings or cylinder liners, and broken crankshaft keyway.

 DiagnosisCommon Causes
Diesel Engine
Leaking coolant or water dripping into combustion chamber• Bad head gasket
• Cracked block or cylinder head
Petrol EngineIncomplete air/fuel
mixture
• Faulty fuel injection system
• Incorrect fuel injection and valve timing
• Engine overheating
• Faulty fuel pump and/or injection pump

Conclusion

There is no room for overlooking the white smoke issue. Not only white smoke affected other vehicles and the environment, it also means your car is in trouble that needs special attention. It may cause problems for you and the other drivers if you don’t fix this before driving.

Yet again, all car owners need to do is to keep calm in order to cure their vehicles. For that reason, always taking care of your engine is highly recommended.

Most of the cars from Japanese brands like Toyota, Honda, Suzuki, Mitsubishi, Nissan… are produced with good engines and high-quality accessories to avoid white smoke from exhaust. Go for a Japanese car to avoid this bad situation.