Check Engine Light White Smoke From Exhaust

If your car exhaust is pumping out white smoke and the check engine light is on, then you’ve probably got a problem with the engine that needs investigating. If you are driving or have just started the engine the causes may be different, so why does this happen and how do you fix it?

If the check engine light is flashing and there is white smoke coming from the exhaust then there is a problem with one or more engine components. The problem could be caused by a cracked cylinder head, cracked engine block, a coolant leak, broken piston rings, or damaged valve seals.

White smoke from the exhaust usually means that water or coolant is leaking into the engine cylinders. This then contaminates the fuel mixture and gets burned up or evaporates and is released as condensation into the exhaust producing white smoke.

Why is my check engine light on and smoke coming from the exhaust? (5 Reasons Why)

Usually when the check engine light comes on it means that the ECU has detected a problem with the engine. If there is also white smoke coming from the exhaust, then this means that something such as water or coolant is getting into the engine and is burning up as part of the combustion process.

Sometimes white smoke can be simply caused by condensation in the exhaust on a cold or damp morning. You’ll notice the white smoke on engine startup and this will disappear 20 or 30 seconds after you start the engine.

However, if the check engine light stays on after the engine starts up and the white smoke doesn’t stop, then you’ve more than likely got a problem with the engine.

Here are some of the causes of continuous white smoke coming from an engine with a check engine light present.

Cause 1: A Damaged cylinder head

blown cylinder head gasket
An overheating engine can cause a blown head gasket and white smoke from the exhaust

One of the leading causes of white smoke coming from your exhaust is a cracked or warped cylinder head. Damage to the cylinder head usually occurs if an engine is constantly overheating and cooling, causing it to expand and contract beyond its normal range.

Once the seal between the cylinder head and the engine block is damaged, coolant may start to find its way from the cooling channels within the engine block into the combustion chambers when the engine is running. This coolant is then heated and escapes through the exhaust as white smoke.

The coolant can also find its way into the engine oil, compounding the problem by contaminating it and reducing its ability to lubricate and cool the engine.

If there is coolant getting into the engine cylinders then this will adversely affect the combustion of the fuel and will cause misfires and problems with the spark plugs. This along with out of range oxygen sensor readings from the exhaust will trigger the check engine light.

Cause 2: Leaking Intake Manifold Gasket

Another common, and often overlooked cause of white smoke from the exhaust is a leaking intake manifold gasket. Some engines have coolant channels running through the intake manifold that keep the manifold cool.

The intake manifold funnels air into each of the engine cylinders and is located directly above the cylinder head. Some engines feature coolant channels within the intake manifold to cool the air going into the engine and to help remove excess heat from the engine cylinders when the engine is running.

Sometimes a crack in the intake manifold or a leaking gasket between the manifold and the cylinder head can allow coolant to drip into the air intake valves of the engine.

This coolant can then make its way into the cylinder and this will affect the combustion of fuel, possibly causing misfires and a check engine light.

Cause 3: A Cracked Engine Block

Another reason for white smoke coming out from the exhaust with a check engine light, is an engine block coolant leak caused by an internal crack in the engine block itself.

Just like the cylinder head, the engine block is sensitive to extreme changes in temperature. Running the engine while it is overheating can cause the engine block to crack around the cylinder bores.

Running the engine with low coolant levels and engine block casting failures are among the leading causes of engine block failure.

Once the engine block fails, coolant may leak into the engine cylinder chambers, and similar to a blown head gasket will cause problems with the contamination of the fuel combustion process that can trigger a check engine light and cause white smoke from the exhaust.

Cause 4: Bad Valve Seals

Problems with the valve seals can also trigger a check engine light, and can allow coolant or oil to contaminate the fuel within the engine leading to white exhaust fumes.

Engine valves regulate the air getting into the engine and exhaust fumes that are leaving the engine. If the seals have started to wear then a small amount of engine oil will start dripping into the combustion chamber from the top of the engine when it is turned off, or when idling.

This can cause white (or light blue) smoke from the exhaust which may trigger the check engine light if the oxygen sensors detect too much oxygen in the exhaust fumes due to a problem with the fuel not burning thoroughly.

A faulty valve seal generally won’t produce white smoke continuously, it usually only happens when the vehicle is left overnight or after the engine has been idling. The check engine light may go off once the exhaust fumes normalize.

Cause 5: Leaking Piston Ring

Damaged piston rings
Damaged piston rings can also cause white smoke

Another less common cause of white smoke and a check engine light is a leaking or broken cylinder piston ring.

If one of the cylinder piston rings is leaking, this can cause a reverse in pressure toward the oil pan. This can force engine oil into the combustion chamber, causing a loss of pressure in the cylinder.

When the oil mixes with the fuel in the cylinder this can cause a range of engine problems that include a drop in engine power, engine misfires, and a decrease in fuel economy.

You will also notice excessive white or blue smoke coming from the exhaust when driving that will trigger a check engine light.

A drop in oil pressure and oil leaking and burning off in the engine cylinders can contribute to the engine overheating. This can cause further damage to the cylinder head and engine block that may lead to coolant leaks within the engine and more white smoke from the exhaust.

What Next: How To Fix Check engine light and white smoke from the exhaust?

This type of check engine light issue can be more difficult to diagnose and repair as it will more than likely involve stripping down the engine to check for coolant leaks and damaged gaskets.

Continuous white or light blue smoke from the exhaust nearly always points to coolant or engine oil leaking into the engine cylinders.

However, it’s still a good idea to check the ECU for error codes before starting as this may help to pinpoint the exact cause of the check engine light and white smoke.

  1. Check the coolant level and check for leaks. The first visual check is to see if there are any obvious coolant leaks. Coolant can leak from damaged hoses, the coolant bottle, or possibly from a bad water pump. Check the coolant level is sufficient in the coolant top-up reservoir when the engine is running and up to temperature. Then check for dried coolant leaks (white chalky residue) around coolant hoses and joints and around the water pump. If the coolant is low, top it up and then recheck it after taking a short drive.
  2. Check the exhaust manifold for cracks. With the engine running, carefully check around the exhaust manifold where it seals with the engine block and along the exhaust for leaks. Water vapor can collect along leaks in the exhaust due to the difference in temperature between the exhaust and the outside air and this can produce white smoke and trigger a check engine light if the oxygen sensors detect too much oxygen in the exhaust fumes.
  3. Check the engine oil level and condition. Check that there is sufficient engine oil, low oil levels may point to an internal leak in the engine. Dip the engine oil and check that it is clean and does not have a milky brown appearance. Dirty or milky engine oil can mean that coolant is getting into the oil somewhere within the engine.
  4. Remove the cylinder head and inspect the engine. This is a last resort and you may need to get a specialized mechanic to deal with this step. Once the cylinder head is removed you can check the inside of the engine for cracks and damage to the seals and gaskets.

FAQ – Check engine light with white smoke from the exhaust

1. Can I drive with white smoke from the exhaust and check engine light?

No, it’s not a good idea to continuously drive if there is white smoke coming from the exhaust and the check engine light is staying on. There is a good chance that the engine is burning coolant and this can lead to it overheating.
If the coolant is leaking through a bad cylinder head gasket then this will only get worse over time and if left unchecked can cause permanent damage to the engine block and cylinder head.

2. Can a clogged catalytic converter cause white smoke and a check engine light?

Yes if the engine is burning oil then this can clog up a catalytic converter and trigger a check engine light. Oily deposits in the exhaust fumes can start to clog up a catalytic converter making it less efficient at filtering the exhaust fumes.
If the engine is running rich (often a side effect of a clogged catalytic converter) then this will generate more white smoke from the exhaust.

3. Can a faulty injector cause white smoke and a check engine light?

Yes a faulty fuel injector or a leaking injector o-ring can cause white smoke and check engine light. Faulty injectors can lead to too much or too little fuel getting into the engine. Too much fuel can cause the engine to run rich, leading to unburnt fuel entering the exhaust manifold and vaporising into white smoke.
This can cause engine misfires and a check engine light if the oxygen sensors detect a problem with the lack of combustion of the fuel.