Home TroubleshootingExhaust Water Coming Out Of Exhaust While Idling – How And Why?

Water Coming Out Of Exhaust While Idling – How And Why?

by Kelvin Yates

Imagine this, you step out to your garage early in the morning, and start your vehicle for the first time of the day. Then, you notice water coming out of exhaust while idling. Has this ever happened to you? Or have you been worried by this? Today, we will tell you all about how and why this phenomenon happens.

Some gearheads believe that water droplets in the exhaust show that the engine is healthy. However, there are many that disagree with this as well. If you own a vehicle and have noticed this happen, you will surely find this article interesting.

We know that you are curious to know why sometimes water comes out of the exhaust pipe, and want to know whether you should be worried about this or not. So, we won’t keep you waiting any longer. Let’s start off by taking a look at the main component we are concerned with, the exhaust system.

How Does The Exhaust System Work

Before talking about water coming out of the exhaust while idling, it is important for you to have a good understanding of the exhaust system as a whole.

water coming out of exhaust while idling

The exhaust system makes use of several components in order to function properly and as intended. The most important parts of the exhaust system are,

  • Exhaust Manifold
  • O2 Sensor
  • Catalytic Converter
  • Hangers
  • Muffler
  • Exhaust Joints
  • Resonator
  • Exhaust Pipe

Now, we will take a closer look at each of these components to better understand what each of them does.

1. Exhaust Manifold

The first component of the exhaust system we will be taking a look at is the exhaust manifold, which is the first section of the exhaust system. It is directly bolted onto the engine block and can be made from a variety of materials like cast iron, aluminum, and stainless steel.

The main function of the exhaust manifold is to collect exhaust gases from each of the cylinders and send them on their way toward the catalytic converter through a single pipe.

That is… Unless you’re experiencing an exhaust manifold leak (most noted for its distinctive exhaust leak sound), which might necessitate an exhaust manifold repair. A repair will be far cheaper than the cost of replacing the exhaust manifold outright.

2. O2 Sensor

The oxygen sensor, more commonly known as the O2 sensor, measures the amount of oxygen gas in exhaust fumes. This sensor is present in most modern vehicles with fuel injection systems. It is mounted either in the manifold or toward the exhaust pipe.

The onboard computer uses information from this sensor to make adjustments to the air-fuel mixture in order to maximize the fuel economy.

3. Catalytic Converter

Arguably, the catalytic converter is one of the most crucial elements of the exhaust system. When the exhaust gases get to this element, a chemical reaction turns the unburnt hydrocarbons, carbon monoxide, and nitrogen gases into carbon dioxide and water which are much less harmful to the environment.

In most vehicles, the catalytic converter is mounted between the muffler and the exhaust manifold.

water coming out of exhaust while idling

4. Hangers

The exhaust system runs through the length of your vehicle as it starts from the engine and ends all the way back to the rear. So, there should be something to hold it in place. This is the responsibility of the handers.

Usually, these are made from rubber. The stretchy nature of rubber makes it possible for them to be stretched between hooks to secure the exhaust system. Additionally, rubber provides friction and noise reduction too.

Furthermore, it is important to mention that hangers come with a universal design. In other words, there are no special hangers for a specific car model. So, you can (mostly) interchange hangers with different vehicle models if required.

5. Muffler

By nature, engines make loud noises due to the internal combustion process and the emission of exhaust gases. However, in order for your vehicle to be road legal, this noise has to be silenced. This is where the muffler comes in unless you prefer a loud exhaust.

The main purpose of the muffler is to quieten the sound of the exhaust down to acceptable levels. Mainly, there are two methods for quieting the exhaust noise. They are absorption and reflection. Usually, mufflers make use of both of these principles to reduce the noise of the exhaust.

Inside the muffler, you will find a series of chambers and tubes. The sound of the exhaust bounces around these components which absorb their energy, reducing the noise in the process. Furthermore, some mufflers contain fiberglass packing to make the sound absorption process stronger.

6. Exhaust Joints

The exhaust system contains four types of exhaust joins. They are flat band joints, U-bolt, V-band clamps, and ball & socket. These joints secure the slip-fit pipe connections to the hangers and do not require any welding to attach to the body.

Without proper joints, there is a high chance of the exhaust system hanging loose and impacting the ground or other obstacles.

7. Resonator

The resonator supports the muffler to minimize and quietens the sound of the exhaust. In other words, it acts like a mini-muffler that is positioned either behind or in front of the muffler. Typically, resonators are straight pipes that are filled with materials that muffle and absorb sound.

8. Exhaust Pipe

The exhaust pipe is what carries the exhaust gases through all the components we talked about earlier. It runs the length of the vehicle, starting at the manifold and ending at the tailpipe which protrudes from the rear of the vehicle and releases the exhaust gases into the atmosphere.

Generally, exhaust pipes are constructed using durable materials like stainless steel, regular steel, or aluminum tubing. As always, there are both advantages as well as disadvantages with each of these materials. Plain steel is cheaper but not as durable as others.

On the other hand, stainless steel is corrosion-resistant and lasts for a long while. Similarly, aluminum is also somewhat rust-proof and cheaper than stainless steel.

As you now have a clear understanding of the most important elements of the exhaust system, it is time to move on with the discussion. Next, we will tell you about the factors that lead to water coming out of exhaust while idling, and what it indicates about the vehicle’s overall condition.

Water Coming Out Of Exhaust

Whether or not you should worry about water coming out of exhaust while idling is a factor that largely depends on the circumstances surrounding the situation. A little bit of water coming out of the exhaust might not always be bad after all. After all, exhaust gases contain some water vapor inside them after all.

Usually, you get an idea about the condition of your engine by looking at the exhaust. Black smoke is an indication of an incomplete combustion cycle caused by an excess of fuel. In the same way, white smoke indicates that water has entered the combustion system, possibly due to a blown head gasket.

So, what does water coming out of the exhaust system actually mean? Well, there are several causes that lead to this condition. Some of the most common ones include,

  • Condensation Of Water
  • Condensation In The Catalytic Converter
  • Faulty Pistons
  • EGR Cooler Issues
  • Blown Head Gasket
  • High Engine Temperature
  • Water Pump Issues
  • Coolant Leak
  • Blocked Exhaust System
  • Crack In The Engine Block

Water Coming Out Of Exhaust While Idling #1 – Condensation Of Water

Condensation is the most probable reason why you are seeing water coming out of the exhaust system. This is not something to worry about, as this is a natural byproduct of the combustion process. In addition to water vapor, other byproducts include carbon dioxide and nitrogen gases.

Once the combustion cycle finishes and the exhaust gases are leaving the chamber, the water particles and carbon dioxide gas gets mixed with each other.


If the engine is given enough time to cool down, these water particles will condense into droplets and come out of the exhaust system.

Ideally, the water drips will stop within a few minutes after you start your engine once again. As we mentioned above, this is completely normal, and you have nothing to worry about.

Water Coming Out Of Exhaust While Idling #2 – Condensation In The Catalytic Converter

We talked about the importance of the catalytic converter in the previous section, and you should know that it can also cause water to drip out of the exhaust. The catalytic converter is designed with the intention of changing the chemical composition of the exhaust gases. So, more water molecules will be produced inside it.

After the conversion process finishes, water molecules will find their way out through the tailpipe. Actually, water dripping out of the exhaust is a sign that shows your catalytic converter is functioning at its optimum. Once again, the water droplets will go away on their own in a few minutes.

Water Coming Out Of Exhaust While Idling #3 – Faulty Pistons

On their own, faulty piston rings will result in blue smoke, sooty exhaust, and the formation of oily residue around the tailpipe. However, when paired with head gasket issues (such as noticing oil in the coolant), problems in the piston rings will cause water to come out of the exhaust system while idling. Furthermore, piston issues will fill up your passenger compartment with a burning smell too.

Unlike the other two issues we discussed so far, this is something that you should not take lightly. If you suspect that there are issues with the pistons, take your vehicle to a mechanic and have them take a look at it. If left unfixed for a long time, faulty pistons (such as piston slap problems) can wreak havoc on your engine.

Water Coming Out Of Exhaust While Idling #4 – EGR Cooler Issues

Vehicles with diesel engines use an EGR cooler to cool down the exhaust gases before they enter the intake. Over time, cracks may form on this part, letting coolant enter the exhaust pipe in the process.

You may mistake this coolant dripping from the tailpipe for water. The best way to distinguish between the two liquids is the smell. If the dripping liquid has a sweet smell, we recommend you take a look at the EGR cooler if your vehicle is equipped with one.

Water Coming Out Of Exhaust While Idling #5 – Blown Head Gasket

A blown head gasket (such head gasket problems are common among some Subarus) is another issue that can result in water coming out of the tailpipe. Sealing the engine block and the cylinder head is the main responsibility of the head gasket, and when it fails, coolant will seep up into the combustion chamber and cause massive issues.

In addition to water coming out of exhaust while idling, head gasket failure has some other additional symptoms as well. Air bubbles in the coolant reservoir and the engine overheating are two that immediately come to mind.

Overall, a blown head gasket is not an issue that should be taken lightly. If not fixed properly, this problem has the capacity to completely destroy your engine. The only solution would be paying up for a costly head gasket replacement cost.

Nevertheless, the latter is still cheaper than fixing severe engine issues caused by a blown head gasket, if not replaced soon. Therefore, you should be attentive to the blown head gasket symptoms early on. These can include issues such as seeing oil leaking from the head gaskets.

Water Coming Out Of Exhaust While Idling #7 – High Engine Temperature

The engine of your vehicle will generate the most amount of heat the moment you start it up. Eventually, the flow of coolant and other lubricants will cool it down. But for those first, few moments, the engine as well as the exhaust will be red hot. That should answer any curiosities about how hot does a car exhaust get.

If the exterior conditions are cold, the heat will create water vapor inside the exhaust pipe. This results in the formation of water droplets, which will continue to drip out of the tailpipe for a few minutes.

Water Coming Out Of Exhaust While Idling #8 – Water Pump Issues

Proper circulation of coolant is essential to prevent any engine from overheating. This is where the water pump comes in. A faulty water pump will cause coolant leaks, releasing water into the exhaust system in the process. So, try to be on the lookout for the symptoms of a bad water pump (you can learn more in our overview of what is a water pump in a car and what does the water pump do in a car).

If you notice an excessive amount of water coming out from the exhaust system, a faulty water pipe might be the one to blame. Replacing a faulty water pump is a straightforward job. Sometimes, other components like belts will need to be replaced as well. The latter will need to be tallied alongside the total water pump replacement cost.

Water Coming Out Of Exhaust While Idling #9 – Coolant Leak

A coolant leak is another common reason that leads to water coming out of the exhaust pipe. So, it’s worth looking into what causes that coolant leak, in the first place. An overheating engine that is running low on coolant will cause water to be drawn into the combustion chamber, leading to water droplets in the exhaust system.

Once you have established that your vehicle is suffering from a coolant leak, there are a few different methods you can try to repair it. The first and cheapest method is using a sealant to seal the leak. But, this is not a permanent fix, and you’ll have to apply the sealant periodically for the best results.

Replacing the leaking hose or the gasket is the ideal method, and it will get rid of the leak permanently. However, as you might have guessed, fixing a coolant leak (immediately diagnosed by quickly looking into low coolant symptoms) in this way is more expensive.

Water Coming Out Of Exhaust While Idling #10 – Blocked Exhaust System

Blockages in the exhaust system due to debris or rust buildup are another prime contender for causing water to come out of the exhaust. Additionally, this can hamper the performance of the vehicle as well.

If you suspect this is the cause, we recommend you take your vehicle to a mechanic as soon as possible. An experienced mechanic will be able to clean out the exhaust system without replacing any components.

But on more severe occasions, you may have to spend some money on a muffler or catalytic converter replacement (just like a Volvo catalytic converter). If you’re too concerned about how much for a muffler replacement, as well as the cost to replace the muffler and exhaust pipe, you can consider a muffler repair cost if the issue isn’t too serious.

Some of those issues include seeing a hole in the muffler. Due to this, you might also look into getting a muffler delete, or looking up where you can get a muffler delete near me. Granted, the latter might lead you into some issues with the law.

Water Coming Out Of Exhaust While Idling #11 – Crack In The Engine Block

The final cause of water coming out of the exhaust we will be taking a look at are cracks in the engine block. Cracks are mainly caused by prolonged overheating, and coolant can flow through these cracks and enter the exhaust system.

If your engine is suffering from a cracked engine block, we have some bad news for you. There is no cost-effective way to repair it, and you’ll have to replace the entire engine block instead.

Water Coming Out Of Exhaust While Idling

If the water is coming out of the exhaust only while idling, you should check the exhaust and engine components for any signs of damage. As we have established, a few drops of water leaking from the tailpipe is not something to worry about.

But, if it is a constant stream of water or the droplets are accompanied by white smoke, it might be a sign of a more severe issue. If that is the case, have your local mechanic go through the vehicle to identify what the matter is.

Water Coming Out Of Exhaust While Running

Ideally, water should not come out of the exhaust when you are driving your vehicle down the road. Although this can be expected sometimes, it is still a good idea to have a mechanic take a look at the issue.

If you are experiencing this problem, take a closer look at the water that is coming out. If you notice that it contains oily residue, there might be some severe damage inside the engine block. Worn-out valve guides, broken piston rings, a bad head gasket, or general wear and tear to the interior engine components can all result in oily water coming out of the exhaust.

Liquid Coming Out Exhaust

The cost to get rid of liquid coming out of the exhaust varies depending on the close. For example, the cost of replacing a blown head gasket can fall anywhere between $1000 – $2000. Similarly, expect to pay between $1000 – $5000 for a piston ring replacement cost.

The cost of these repairs is so high not because of the cost of the parts. Instead, it is in labor costs that you’ll have to pay the most.

These repairs require the whole engine to be taken apart, which requires a lot of time and makes them very labor-intensive.

You might consider not going through with these repairs due to the astronomical costs involved. However, this will do your wallet more harm than good. Leaving these issues unsolved will ultimately end up destroying the engine, needing you to replace it entirely. Just imagine the parts and labor cost of that!

Final Verdict

As we have established, a small amount of water coming out of exhaust the moment you start your engine happens due to natural condensation, which is nothing to worry about. But, if the water keeps dripping out for a long while, it might be a sign of something sinister.


Head gasket issues, a defective EGR cooler, a blocked exhaust system, or a faulty water pump can all result in water droplets dripping out of your tailpipe. If the water does not stop, the best course of action is to take the vehicle to your local mechanic in order to have them take a look at it.

FAQs On Water Coming Out Of Exhaust While Idling

How Hot Does A Muffler Get

Typically, with the engine turned on, the temperature inside the muffler can reach around 300 – 500 degrees Fahrenheit. The entire exhaust system is made to withstand temperatures as high as 1600 degrees.

What Causes Exhaust Leaks

There are many factors that can lead up to exhaust leaks. Some of the leading causes include damage from frequently driving over rough terrain and corrosion. Reduction in fuel economy, along with increased engine noise, and fumes in the cabin are some symptoms you can use to identify exhaust leaks.

How Hot Does Car Exhaust Get

Along with the engine, the exhaust is one of the hottest areas of a vehicle. Here, the temperature can range anywhere between 600 to 930 Fahrenheit, but it has been reported to get as high as 1600 degrees in some vehicles.

Why Does Water Come Out Of My Exhaust

Water can come out of the exhaust due to a number of reasons. The most common one is condensation, which is a natural process that you shouldn’t worry about. Other causes include damage to the EGR cooler, blown head gaskets, engine block damage, faulty piston rings, and debris buildup in the exhaust system.

What Comes Out Of Car Exhaust

The main responsibility of the car exhaust system is to release byproducts of the combustion process from the engine to the outside. Furthermore, the exhaust system is designed to muffle the sound of vehicles as well. The gases that come from the exhaust system contain several toxins such as carbon monoxide, nitrogen oxide, and nitrogen monoxide.

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