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How To Locate & Repair Antifreeze Leaks | (Complete Guide)

An antifreeze leak is bad news for your car’s cooling system. Antifreeze leaks can quickly cause overheating, and substantial engine damage could result if the leaks are left unrepaired. Some believe that antifreeze only prevents your engine from freezing, but it also cools your engine as well.

A coolant leak can occur at many different places in your engine, from the radiator to the water pump. Most of the time, there will be symptoms that you have a coolant leak. When you notice any of these symptoms, you should take care of the problem right away. Keep reading as we tell you some of the most common causes of an antifreeze leak and how to locate and repair those leaks.

What Is Antifreeze?

Antifreeze is primarily made of ethylene glycol, and it lowers the freezing point of water. When your vehicle’s cooling system is filled with antifreeze, the freezing point is lowered to around -37 degrees Fahrenheit. This is why you do not fill your cooling system with water. If you did, the water would freeze and could crack your engine block. Instead, you typically use a mixture of water and antifreeze to achieve optimal freeze protection.

Not only does antifreeze lower the freezing point of a water solution, but it also raises the boiling point. Typically, the boiling point of the coolant is raised to around 320 degrees Fahrenheit. This allows your coolant to circulate through the engine and remove heat from the engine without boiling. In addition to these important properties, antifreeze also provides lubrication for some parts of your engine. Coolant helps lubricate your water pump, and it provides far superior lubrication than pure water.

Signs That Your Car Is Leaking Antifreeze

How do you know when your car is leaking coolant? There are a few symptoms that you are likely to see. If you notice any of these symptoms, you should head to an auto repair shop soon to have the problem repaired. Here are the things you should watch for.

— Overheating

Engine overheating is one of the most common symptoms of a coolant leak. When your coolant leaks from the cooling system, the coolant level gets too low. The engine overheats when there is not enough coolant in the system to keep things properly cooled. Overheating can also be caused by a few other things, like a faulty thermostat, a bad water pump, or a blown head gasket. If you notice your vehicle overheating, take a look at the coolant reservoir. If the coolant level is low, then you can be sure you have a leak somewhere.

— Puddles Underneath Vehicle

Drops or puddles of coolant underneath your vehicle absolutely signal a coolant leak. Just make sure that you know what the liquid is. Leaking engine oil could also create a puddle under your car, but oil and coolant have completely different colors and smells. Coolant is typically bright green or orange, and it has a sweet smell. If you confirm the liquid is coolant, you shouldn’t drive your car until you diagnose the problem. You could have a significant leak that needs to be repaired before driving anywhere.

— Sweet Smell

Antifreeze has a sweet smell, and you can often smell the leak before you see it. You may notice the sweet smell coming from under your hood, or it might be apparent in the vehicle’s cabin. When you have an antifreeze leak in the heater core, you might notice that the carpet in the car is wet. When this happens, you will almost always notice the sweet smell in your car. If you notice this smell, especially when the heater is blowing, you should get your vehicle checked by a mechanic as soon as possible. It is very likely that you have a coolant leak somewhere in your car.

Common Causes Of An Antifreeze Leak

Now that you know the symptoms of an antifreeze leak, you are probably wondering what would cause a leak. Antifreeze leaks can occur for several different reasons, but here are the most common causes.

— Cracked Radiator

A cracked radiator is one of the most common causes of an antifreeze leak. Your car’s radiator sits at the front of your car, directly behind the grille. It extends from the top of the engine bay and sits close to the ground in most cases. Rocks and other road debris are notorious for damaging radiators. Hitting debris at highway speeds can lead to radiator damage that causes leaks. In addition to damage, radiators can develop leaks due to corrosion. Old antifreeze starts to turn acidic, and it can corrode the internal parts of your radiator and lead to small holes or cracks. A cracked radiator will leak antifreeze, and you will often see drops of antifreeze underneath your car when this happens. If you have a radiator leaking coolant, you need to get it repaired right away.

— Faulty Radiator Cap

Your car’s engine coolant is pressurized in the cooling system as you drive. Pressurizing the coolant increases the coolant’s boiling temperature, allowing the cooling system to remove heat from the engine more effectively. The radiator cap is important in allowing the system to build pressure. If the cap is faulty, it might start to leak as the pressure builds. Instead of keeping the system sealed, the cap can allow coolant to escape. Not only could the lack of pressure cause your car to overheat, but the leaking fluid will lead to a low coolant level. If you notice your temperature gauge creeping up, it might be due to a faulty radiator cap. Make sure that you never attempt to inspect or remove the radiator cap with the engine running or while it is hot! Coolant could spew from the system and cause severe burns. Let the engine cool completely before attempting to diagnose the radiator cap.

— Radiator Hose Problem

Rubber hoses get hard and brittle as they age, and radiator hoses are no exception. Sometimes an old hose will simply burst because it can no longer withstand the heat and pressure in the system. This immediate failure of a radiator hose will require you to shut off your vehicle until the hose is replaced. Hose clamps can also become loose over time. When the clamps become loose, they might no longer hold a tight seal between the radiator or thermostat and the hoses. These connection points can start to leak, and it might take you a little while to notice the leak. If you notice that your coolant reservoir is getting low but don’t see any obvious leaks, you should inspect all the hose connections to see if any of them appear wet.

— Blown Head Gasket

A blown head gasket is one of the worst causes of an antifreeze leak that you might experience. In the case of a blown head gasket, antifreeze leaks inside the engine. Instead of flowing through the passages between the engine block and cylinder heads, the antifreeze can escape into the cylinders and combustion chamber because the gasket no longer provides a good seal. When this happens, you will likely notice white smoke from your exhaust as the antifreeze burns. In severe cases, you might even experience a hydrolocked engine. If you see white smoke from your exhaust and a high engine temperature, you can be certain that you have a blown head gasket.

— Bad Water Pump

The water pump’s primary function is to pump coolant through the engine and coolant system to keep the engine at its proper operating temperature. A couple of things can cause the water pump to develop small leaks. First, the gasket that seals the water pump to the engine can go bad. Next, the radiator hose that connects to the water pump can become loose. You might experience a leak at this connection point. Finally, the seals or bearings in the water pump itself can fail. When this happens, you might see coolant dripping directly from the water pump. Depending on how your engine’s cooling system is designed, the water pump might be mounted to the outside or inside of the engine. Replacing a water pump that is mounted inside is much more expensive, and it can cost you up to $2,000 in some cases.

— Damaged Heater Core

Your heater core can be another potential source of the leak when you notice your coolant level getting low. The heater core sits inside the dashboard of most vehicles, and it plays a critical role in the operation of the vehicle’s heater. When you turn on the heater in your car, hot coolant from the engine flows into the heater core. A fan blows across the core and moves the hot air into the car’s cabin. Heater cores can develop internal leaks or have leaks at the connection points of the hoses. Most of the time, you will notice a sweet smell in the car or wet carpet due to the leak. Replacing a heater core is a big job that is quite expensive, and most people will need the help of a mechanic to perform the replacement.

— Damaged Coolant Reservoir

Your car’s coolant reservoir holds coolant inside as a sort of reserve for the system. If the cooling system gets low on coolant, the system can pull more coolant from the reservoir. Sometimes, excess coolant from the system needs to flow into the reservoir as the coolant in the system expands. The reservoir is simply a plastic container in most cases. The reservoir can develop small cracks that leak. If you notice leakage around the coolant reservoir, it might need replacing. While this is not an extremely common reason for an antifreeze leak, it can happen.

Locating And Repairing An Antifreeze Or Coolant Leak

If you have noticed the fluid level in your coolant reservoir getting low, you have a leak somewhere in the system. So, how do you locate and repair that leak? First, you need to start with some inspection and diagnosis. Take a look under your vehicle and inside the engine bay for obvious signs of a leak. You might notice hose connections that are wet or even see coolant dripping from the radiator. A radiator leak will be fairly obvious most of the time, although a leak from a blown head gasket will not display the same symptoms. Similarly, the work required to perform a radiator repair will be much different than replacing a blown head gasket.

Once you have located the problem, you will need to repair it. Most of the time, this requires the replacement of the faulty part. This could include the replacement of the thermostat, radiator cap, radiator, or head gasket. Installing a new radiator in your car is a repair that you might be able to complete yourself if you have the proper tools and mechanical knowledge. However, most car owners will need a mechanic to perform this repair. If the radiator has only a very small leak, you can attempt to use a sealant to fix the problem. Simply pour a bottle of sealant, such as Bar’s Leaks Stop Leak, into the radiator. If the leak does not stop, you will need to replace the radiator.

The Bottom Line

If you have a car leaking antifreeze, you should diagnose and fix the problem right away to avoid engine overheating. You might see drops of fluid under your car or notice your temperature gauge getting too high, and either of these scenarios is a sign of a coolant leak. It could be coming from many different sources, including a cracked radiator, bad radiator hose, faulty heater core, or blown head gasket. Make sure that you properly diagnose the cause of the problem before attempting to fix it. Repairing an antifreeze leak could be as cheap as $20 or as expensive as $3,000, depending on your vehicle and the source of the issue.

Frequently Asked Questions

How much does it cost to fix an antifreeze leak?

Coolant leak repair costs depend heavily upon the cause of the leak and the make and model of your vehicle. Replacing a faulty radiator cap can cost less than $10 in some cases. However, replacing a blown head gasket could cost you $3,000 or more. On average, you can expect to pay around $500 to repair a coolant leak. Replacing a blown radiator hose might only cost you a couple of hundred dollars, while replacing your leaking radiator is likely to run more than $500 on most vehicles.

Can you drive with an antifreeze leak?

You should not drive your vehicle with a fluid leak in most cases, and driving with an antifreeze leak is usually a bad idea. However, if the leak is very small, you should be OK to drive a short distance. You will want to make sure that you keep a close eye on your coolant level and keep the system filled to the appropriate level. If your engine overheats due to low coolant, you could cause extensive damage to the engine. You should never drive with a large coolant leak. Your engine can overheat quickly, and severe damage, such as a cracked engine block, will likely occur.

How serious is an antifreeze leak?

A leaky radiator or any other antifreeze leak is a serious problem. You should not ignore antifreeze leaks, and you should have them repaired as soon as possible. If the leak is large enough, you cannot drive your car with the leak. On the other hand, if the leak is minimal, you can drive a short distance as long as you keep a close eye on the coolant level. However, small leaks usually get worse with time. A small leak may turn into a big leak, and you might be stuck on the side of the road with an engine that has overheated.

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