Water coming out of your exhaust can be a simple sign of condensation settling in the exhaust system while the car sat and cooled down. It’s when the volume of water is more than perhaps a few tablespoons, or it persists while the car is running and fully warmed up that you need to worry about a more serious problem brewing in your car’s exhaust system.
Serious problems related to water coming out of a car’s exhaust include things like catalytic converter problems, a blown head gasket in the engine, bad piston rings, or a damaged EGR valve.
To help you dial the severity of the problem, we’re going to have to take a little bit more of a deep dive into the most common reasons why you have water coming out of the exhaust, how to diagnose the fault, and what you might be able to do about it.
Why Is Water Coming Out of My Car’s Exhaust and What Should I Do About It?
Water coming out of your exhaust when you first start the car isn’t really a major cause for concern. This is usually just condensation that built up in the exhaust system while the car cooled down. Over time, there’s a worry about this condensation causing rust in the muffler, but on its own, a few early dribbles of water coming out of the exhaust isn’t usually a standalone sign of a major fault.
The Top 6 Causes of Water in the Exhaust
There are some more serious causes of water in a car’s exhaust that you need to pay attention to. This includes problems with:
1. Condensation in the Exhaust System
When your car is running the exhaust system is very hot. When you stop the metal cools and ambient humidity can condense inside the tailpipe and muffler. It sits there until the next time you start your car, where the force of hot exhaust blows a small volume of water out of the tailpipe.
A few drips for a minute or two generally isn’t a big deal, and is completely normal. At most there’s a long term concern that the water in the exhaust system could rust the muffler or tailpipe. It’s when you have a more serious volume of water, or the water keeps coming out of the exhaust long after the car is fully warmed up that you might have a more serious issue brewing.
2. A Problem with the Catalytic Converter
Water in the exhaust can sometimes be caused by condensation occurring deep within the catalytic converter. The catalytic converter marries the internal exhaust system of the engine to the tailpipe and muffler. It changes the chemical composition of the gases produced by the internal combustion process, which can create a small volume of water molecules.
A little bit of water after starting the car isn’t a big deal. Though if you keep having water coming out of the tailpipe you should suspect a more serious problem.
How to Diagnose a Catalytic Converter Problem
A bad catalytic converter with water coming out of the exhaust will also be down on power with poor gas mileage. You might also notice a rattling sound when accelerating and the check engine light coming on or flashing. You might also smell foul sulfurous rotten egg odors coming out of the exhaust.
You should also strongly suspect a catalytic converter problem if the car has recently been misfiring. This is a sign that unburned fuel from the cylinders has been migrating through the exhaust system damaging the catalytic converter.
How to Fix a Bad Catalytic Converter
A mechanic might be able to fix a minor problem with a catalytic converter. Though for there to be any chances of this, you need to catch the problem early. If your catalytic converter was damaged by unburned fuel residue from a recurring engine misfire problem, then chances are good it will need to be completely replaced.
The cost to have a mechanic replace a catalytic converter can vary from $900 to $2,500. With most of the cost coming from the part itself. If you have a slightly older vehicle, you might be able to save a lot of money on parts by sourcing the new catalytic converter from a junkyard or an auto salvage company.
3. A Problem with the Head Gasket
If you have water coming out of the exhaust along with white smoke, you very likely have a head gasket problem. The head gasket seals the engine’s internal combustion chamber to allow it to build up the necessary compression to maintain power, while also keeping coolant and oil from leaking away. This further plays a critical role in keeping the engine running within the normal temperature range.
How to Diagnose a Head Gasket Problem
A head gasket problem will often manifest as water coming out the exhaust with white smoke, and an engine that is low on coolant and/or oil. This usually causes the engine to run hot. You might also notice the top of the oil cap is messy and bubbles in the radiator fluid.
A cracked head gasket essentially means that coolant and/or oil is making its way through the fault in the head gasket and exiting the exhaust system. Left unchecked a bad head gasket can become a monstrously expensive repair bill!
How to Fix a Bad Head Gasket
If you catch it early, and the gasket is only slightly compromised, you might be able to temporarily fix a bad head gasket with some relatively inexpensive head gasket sealer. This calls for pouring a modest amount of head gasket sealer liquid directly into your radiator.
Then immediately drive the car for at least 15 to 20 minutes to give it time to circulate through the system. Turn the car off and let it cool down for an hour or two before rechecking for leaks.
Head gasket sealer isn’t a permanent fix. Though you should be able to get at least three to perhaps six months out of it if the head gasket problem is minor.
If the head gasket sealer doesn’t fix the problem, then the head gasket needs to be replaced. This isn’t the sort of thing the average do-it-yourselfer can handle.
The cost to have a professional mechanic replace your head gasket ranges from $1,500 to $2,500. With the cost for parts being about half of the total bill.
4. Bad Piston Rings
When a bad head gasket goes undiagnosed it can lead to bad pistons and damage the rings, which will also cause water coming out of the exhaust along with oil residue. This is a major fault that is usually expensive to fix.
How to Diagnose Bad Piston Rings
Bad piston rings start out with a lot of the same symptoms as a head gasket problem, though you will also notice a significant loss of power and increasingly poor acceleration. You might also notice an oily residue with the water coming out of the exhaust.
How to Fix Bad Piston Rings
In a few rare cases, you might be able to fix a minor problem with the piston rings by spraying Sea Foam through the engine intake manifold or spraying it directly into cylinder cavities. The goal is to let it soak the pistons cleaning rings from the top end. You can then use oil with a thicker-than-normal viscosity to help the rings maintain a better seal.
Though this is usually only the case if you caught a head gasket problem early, just started to affect the piston rings. It’s usually only a temporary fix that might buy you a few weeks or perhaps a few months.
Most of the time when a bad head gasket, engine heating, and time cause bad piston rings with water coming out of the exhaust, you need the rings replaced. This might also include repairing or replacing multiple pistons.
The cost to have a mechanic repair bad piston rings can vary from $1,000 to as much as $5,000 depending on if there is damage to the actual piston or the cylinder walls. If it’s just the rings that need to be replaced, the final bill will end up being around $3,000 to $3,500.
5. A Crack in the EGR Cooler
If your car has a diesel engine and there’s a persistent problem with water coming out of the exhaust, you might have a cracked EGR cooler. This is a special device installed in a lot of newer cars and vehicles with a diesel engine that helps cool the exhaust gases. When it’s cracked it can affect performance leading to moisture and residual coolant getting into the car’s exhaust system.
How to Diagnose a Crack in an EGR Cooler
It’s designed to cool the exhaust, but can be prone to cracking, which allows a small volume of coolant and water to come out of the exhaust. If this is the case the exhaust and drips of water will smell overly sweet. You might also notice the check engine light coming on or flashing.
The longer you drive with a cracked EGR cooler the more you’ll notice water coming out of the exhaust followed by a rough idle. These are overt signs that the engine is getting stressed and you might be looking at an even worse repair bill.
How to Fix a Crack in an EGR Cooler
Fixing a crack in an EGR cooler is not the sort of thing a do-it-yourself mechanic can handle on their own. A lot of times you need a mechanic to completely replace the EGR cooler to prevent more serious engine and/or exhaust system damage.
The cost to have a mechanic replace your EGR cooler can range from $350 to $450. With about three-quarters of that cost being for the part itself.
6. The Engine Is Running Hot and/or Overheating
When you have water coming out of the exhaust and the car is running hot it’s usually related to condensation inside the engine. This is sometimes more common in deep cold weather and isn’t necessarily a sign of a problem on its own.
Where you need to worry is if the engine is running so hot that it’s overheating after the water starts coming out of the exhaust. This might be an early symptom of a head gasket problem or some other type of fault in the car’s cooling system.
Frequently Asked Questions
Is it normal for water to come out of the exhaust?
A little bit of water coming out of the exhaust within the first few minutes after start-up is completely normal and to be expected. It’s when water continues to come out of the exhaust and you notice other symptoms like white smoke, high engine heat, low coolant, or low oil that you should suspect there’s a more serious problem going on.
Can water in the exhaust damage my car?
Water coming out of the exhaust from condensation, without any other sort of mechanical fault is a minimal threat. Though with older vehicles that are allowed to sit for days at a stretch or aren’t driven very often water coming out of the exhaust can lead to an increasing problem with rust in the muffler and tailpipe.
I once had a 17-year-old pickup truck that was primarily used for farm work and snow plowing that suffered severe exhaust system rust from condensation due to low usage. Yet it only had 145,000 miles on the engine!
Is it safe to drive with water coming out of the exhaust?
If you have water coming out of your car’s exhaust with other signs of a mechanical fault, such as a bad head gasket, faulty piston rings, or a catalytic converter problem, you shouldn’t push your luck. You can limp the car home, to the auto parts store, or the mechanics, but you shouldn’t drive it anymore until it’s properly fixed.
white smoke, oily residue, and the engine is running hot, then you likely have some degree of head gasket failure. This might also include bad piston rings.
If the water coming out of the exhaust has a sweet aroma, and you are slightly low on coolant, you can still drive for a little while with a cracked EGR cooler. Though this is a matter of a week or two. Any longer than that and you risk more major damage to the engine.
Water coming out of your exhaust when you first start up the car isn’t a big concern. It’s usually just condensation that builds up once the car cools down and sits for a few hours.
It’s when you have water in the exhaust along with other signs such as white smoke, oily residue, low coolant or the engine is running abnormally hot, that you might have a more serious problem. This could be a catalytic converter problem, a bad head gasket, bad piston rings, or a crack in the EGR cooler.
If it’s a minor head gasket issue, you might be able to get by for 3 to 6 months with a head gasket sealer. If it’s a minor catalytic converter issue, a mechanic might be able to repair it cheaply. Pretty much all other mechanical problems that cause water to come out of the exhaust require more major repairs.
These are often beyond what a do-it-yourself-mechanic can handle. So, be prepared for a repair bill that’s upwards of $1,000 or more.
Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.