Causes of coolant in exhaust but not in oil | solutions

Cars comprise different fluids that keep your engine functioning well. However, they are supposed to remain in certain compartments or flow through certain channels to do their jobs. But when something goes wrong, they may appear in other places in your car, such as the exhaust, causing problems.

Vehicle owners have reportedly complained of having coolant in exhaust pipe, though not in oil. So they are worried about why it happens and possible ways to fix it as this situation can cause more damage if not handled timely. But before discussing how to fix the problem, why is there coolant in exhaust but not in oil?

coolant in exhaust but not in oil

Causes of Coolant in Exhaust But Not in Oil

Generally, when people observe exhaust smells like coolant, there is always a possibility that water is also in their oil. However, when it is found coolant in exhaust, but not in oil, the causes may differ. You may have a cracked head block, a blown head gasket or an antifreeze passage leaking for coolant from the exhaust pipe. Let’s go into depth.

1. Blown head gasket

If there is coolant coming off your car exhaust, there is a high chance that you have a blown head gasket. The head gasket helps seal your engine block and top cylinder, so fluids do not escape into places they are not needed.

However, when it develops a crack or a weak spot, it can allow coolant from the coolant passage to leak into your engine cylinder. The coolant in the cylinder then gets pushed out by the pistons via the exhaust valves onto your exhaust system.

In most cases, the oil will be mixed with coolant which results in reduced engine power. But it can sometimes happen without mixing with the motor oil.

2. Leaky coolant passage

Coolant gets transported via hoses from your cooling system to other parts of the vehicle that needs it. If any of these hoses get loose or broken, coolant can get into your exhaust system and come out through the tailpipe. And would usually get more noticeable when you start the car and leave it idle.

Like in a 2003 Chevy Tahoe diagnosed with this problem, coolant began leaking out profusely from both exhaust and fenders when the engine was left at idle. Go under your car with your engine running to see if you will notice any hose leaking.

3. Cracked head block

Another apparent cause of high performance Coolant coming out of exhaust, especially when there is coolant in oil. The intake gasket is a seal between the intake manifold and cylinder head, ensuring coolant or air does not reach where these two components meet. If, however, the head block cracked, coolant can find its way into the cylinder, where it gets pushed out by the piston into the exhaust.

How Do I Know If There Is Antifreeze In My Exhaust?

An easy way to know there is antifreeze in exhaust pipe is to watch out for the liquid coming off the exhaust. However, this liquid could also be water as water could form on the exhaust due to condensation when the exhaust is getting cold.

To be sure it’s coolant coming off your exhaust, you can taste the liquid and spit it out. Coolant usually has a sweet smell; if it is water, it would have no taste at all. Another way to know if it’s coolant is the color; coolant is a green fluid though it can be red, pink, orange, yellow, or blue.

Again, if truly what you see is a coolant, you should notice a coolant smell from exhaust or thick smoke coming out of the tailpipe during engine start-up, and it worsens when the leak is severe. Please note that an exhaust leaking out coolant is different from just a sweet-smelling exhaust. What does this mean?

While an exhaust leaking out coolant will also smell coolant, there are cases where you would only perceive the smell but not see any coolant. For example, if your exhaust smells like antifreeze, but there is no visible coolant leak from your exhaust, it means one thing. Your coolant has found its way into the combustion chamber, burnt there, and emitted in the form of exhaust smoke through your tailpipe.

This could also be due to a blown head gasket and even a cracked intake gasket, but in this case, the coolant doesn’t go directly into the exhaust but into the combustion chamber, where it gets burnt and emitted as exhaust gas. So you will get head gasket smell but not losing coolant from the exhaust pipe.

What Does It Mean If Coolant Is Coming Out Of The Exhaust?

If coolant is coming out of your exhaust, one or several seals sealing your coolant are broken, which could be the head or intake gasket. In other cases, it could be that the hose circulating the coolant is leaking. It could also mean a leak in the radiator housing the coolant.

Coolant leaking from exhaust pipe could be due to other reasons, but the most common ones are bad head or intake gasket, leaky coolant passage, or radiator.

How to fix coolant in exhaust pipe but not in oil

A great way to fix coolant in the exhaust, whether the coolant is leaking from the exhaust pipe or you’re only smelling it, is to know the cause. While we’ve established possible causes of coolant in the exhaust, carrying out a proper diagnosis would lead you to its actual cause. Here you could do a compression or pressure test. See possible ways to fix coolant in exhaust.

  • Head gasket coolant leak, cracked intake gasket, or leaky radiator can be fixed using a stop leak, especially when the damage is not too severe. If, however, it is irreparable, you will need to change these components.
  • Change leaky or broken coolant hose.
  • Hydrocarbons must have mixed with your coolant If the issue is a head gasket problem. This means testing for hydrocarbons is another way to detect if it’s a head gasket causing coolant in the exhaust. If there is a hydrocarbon in the coolant, flush out coolant out of the system totally alongside sealing or replacing the head gasket.
change leaky hose


What happens if coolant gets into the exhaust?

When coolant enters the exhaust, you will notice visible coolant leaking from the exhaust pipe. You would also notice white smoke from the tailpipe that worsens as the leaks get severe.

You may also experience a coolant shortage which can lead to overheating since the engine isn’t getting enough coolant to cool down. This can invariably lead to engine damage.

What does coolant in exhaust smell like?

Coolant in exhaust has a sweet flavor. However, if the coolant has found its way onto your combustion and burned there, you will perceive a cinnamon-like smell via your exhaust. This indicates that you may have a bad head gasket or cracked cylinder head allowing radiator fluid into the combustion chamber.

Why is my coolant not circulating through my engine?

Coolant may not circulate through your engine for several reasons. It could be that the thermostat allowing coolant to circulate is clogged or stuck in a close position. It could also be that your radiator is clogged or the coolant passage leaks.

Will a blown head gasket leak coolant?

Yes, a blown head gasket will leak out coolant. Aside from sealing the combustion chamber, the head gasket prevents coolant and oil from leaking into where it’s not needed. If, however, this gasket gets blown or damaged, it will leak out coolant. Add coolant if the level is too low.

How expensive is it to replace a head gasket?

Head gasket replacement lurks around $1624 – $2000. While the parts depending on your car, ranges from $700 – $900, labor costs around $900 – $1150


If you have coolant in exhaust, but not in oil, chances are that your head or intake gasket is bad, or you have a leaky coolant passage or radiator. An excellent way to fix this is to carry out a proper diagnosis to ascertain the real culprit.

If you have a cracked intake gasket, head gasket, or radiator, you can seal it using a head gasket entirely from the system if you detect hydrocarbons in the coolant. Allowing these problems to persist will only cause more engine damage, so fix them immediately.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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