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Common Causes Of Coolant Leaks | How To Find & Repair Them

Your car’s cooling system is critical to keeping your engine running at the correct operating temperature. Any problems with the cooling system can lead to your engine overheating, and that can quickly cause significant damage. Overheating could lead to a blown head gasket, a cracked engine block, and other critical problems.

Coolant leaks are one of the most common problems you might experience with your cooling system. Leaks can come from many places, like the radiator, hoses, water pump, and other places. So, what are the most common causes of a coolant leak? Keep reading, and we’ll tell you what is most likely to cause a coolant leak. We’ll also give you tips on how to find and repair those leaks.

Common Causes Of A Coolant Leak

There are several symptoms of an antifreeze leak in your vehicle. Symptoms can range from puddles under your car to a sweet smell from the engine bay. Overheating is also one of the most common signs that you have a coolant leak. But what causes these leaks? Here are the most common causes of a coolant leak in your car.

— Cracked Radiator

A cracked radiator will absolutely cause leaking coolant. There are a few different reasons that a radiator might develop a crack. First, road debris might damage the radiator. Since the radiator sits at the front of the vehicle, it is susceptible to damage from rocks or other debris on the roadway. If a rock hits the radiator at 60 miles per hour, damage is likely to occur. Internal corrosion can also cause your radiator to leak. As coolant ages, it becomes acidic and starts to corrode parts of your cooling system.

Since coolant is constantly inside the radiator, even a small crack will lead to a leak. Is your radiator leaking? Depending on the severity of the leak, your coolant level might drop quickly. Most of the time, radiator leakage will lead to a small puddle or at least a few drops of coolant on the ground under your car. Have a mechanic examine your vehicle to determine the cause of the problem and get it repaired.

— Faulty Radiator Cap

Believe it or not, your radiator cap is an important piece of your car’s cooling system. Your coolant is pressurized in the system, and the radiator cap plays a significant role. The cap is designed to withstand a certain amount of pressure. The pressure in the system raises the boiling point of the coolant and helps the engine run at the proper operating temperature. If the radiator cap fails, it can allow coolant to escape as the pressure builds in the system.

When coolant leaks out of the radiator cap, you are likely to see drips or puddles underneath your vehicle. You might even see a small amount of steam or white smoke coming from under the hood. Never attempt to remove the cap while your engine is hot! Hot coolant could erupt from the radiator and cause severe burns if it touches you. Once the engine cools completely, you can then attempt to remove and replace the cap.

— Radiator Hose Problem

Your radiator hoses are responsible for carrying the coolant from the engine to the radiator and back. Leakage from hoses is not uncommon, and there are a few different places where the coolant could leak. First, you could experience total failure of a hose. As the rubber hoses on your vehicle age, they become stiff and brittle. It is not uncommon for an old hose to burst and spew coolant from your vehicle’s cooling system. You should always keep a visible check on your hoses for any cracks or signs of wear.

Next, you might experience a leak due to the hose connections. Hose clamps are typically used to hold the hoses on the radiator and engine, and these clamps can loosen over time. The hose connection to the thermostat is another common source of the leak. You might notice that some of these connections are wet to the touch. If that is the case, then coolant is likely leaking from the connection. Most of the time, the entire hose will need to be replaced to repair the issue.

— Blown Head Gasket

A leaking radiator might seem bad, but a blown head gasket is probably one of the worst reasons for a coolant leak. Not only can the problem cause additional damage to your car’s engine, but the cost of repairing a blown head gasket is expensive. Excess heat or pressure are the main reasons for head gasket failure. Since these gaskets are usually made of rubber or a composite material, they don’t last forever. When they fail, coolant is likely to escape into your engine’s combustion chamber.

Some of the main signs of a blown head gasket include a loss of compression, white smoke from the exhaust, overheating, and a low coolant level. You might not notice any fluid leaks on the outside of the engine, as the coolant might only be leaking internally into the cylinders. If you notice your temperature gauge constantly creeping up, along with white smoke or loss of power, then you likely have a blown cylinder head gasket. Get it checked right away before you cause additional engine damage.

— Bad Water Pump

The primary function of your water pump is to circulate the coolant through the coolant system. The water pump is responsible for pumping coolant through the engine, to the radiator, and back into the engine. Similar to how an oil pump circulates engine oil through the engine, the water pump does the same with engine coolant. Over time, water pumps can develop small leaks. Sometimes, the leak occurs due to a bad gasket where the water pump attaches to the engine. At other times, the water pump itself develops a leak due to bad seals or bearings.

Water pump failure is one of the most common reasons for an engine coolant leak, and some water pumps are easier to replace than others. Some water pumps are mounted on the exterior of the engine, while others are mounted inside near the timing belt. If you notice the level in your coolant reservoir dropping, the water pump should be one of the first items you inspect. Similarly, if the engine overheats when only driving a short distance, the water pump is very likely to blame.

— Damaged Heater Core

Many people are not even sure what a heater core is, but this part can be the cause of low fluid levels for your coolant. The heater core is located inside the dash of most vehicles, and the hoses that run to the heater core pass through the firewall at the back of your engine bay. The heater core is one of the main components of your car’s heater. It uses heat from the engine to blow into the passenger compartment. It does so by passing hot coolant through the heater core, and fans blow the warm air from the core into the cabin.

Your heater core can develop a leak, just like your radiator. In fact, the heater core is very similar to a small radiator. In addition to the heater core itself, the hoses or connections to the core can also develop leaks. If you notice that the carpet in your vehicle is wet or you notice a sweet smell inside your vehicle, you might have a problem with the heater core. You should head to an auto repair shop soon to assess the situation.

How Your Car’s Cooling System Works

To better understand the potential causes of leaks, it helps to have a basic understanding of how your car’s cooling system works. This particular system in your vehicle is not overly complicated. Here are the basics.

When you start your engine, the water pump begins to circulate coolant through the engine. The coolant flows through many small passages in the engine — both in the engine block and the cylinder heads. While the engine is still fairly cool, the coolant only circulates through the engine. It does not flow to the radiator. The reason for this is the engine operates most efficiently once it reaches its operating temperature. While the engine temperature is low, the engine needs to warm up quickly. Therefore, heat does not need to be removed from the engine yet.

Once the engine reaches operating temperature, the thermostat opens. When the thermostat opens, the hot coolant flows into the radiator. As the coolant passes through the radiator, heat is exchanged into the outside air. This heat exchange is assisted by thousands of tiny metal fins on the radiator.

After the heat has been removed from the coolant in the radiator, the coolant is pushed back into the engine to remove heat from the engine once again. This cycle of removing heat from the engine, going into the radiator, cooling inside the radiator, and going back into the engine repeatedly continues as you drive. As your speed increases, the heat is removed from the coolant by the air passing over the radiator fins. However, if you are sitting in traffic, there is no airflow to help remove the heat. This is when the cooling fans on your vehicle will come on. The fans blow air over the radiator to help remove the heat from the coolant.

How To Perform A Coolant Leak Repair

So, are you wondering how to fix a leaking radiator? The repair for a coolant leak really depends on the source of the leak. Repairing a leaky radiator is much different than repairing a blown head gasket. If you have a small leak in your radiator, you might be able to pour a bottle of Bar’s Leaks Stop Leak into the system. This product is a sealant that can seal and repair small leaks in the radiator. You might also be able to have a mechanic weld or repair small cracks in the radiator. In some cases, a mechanic might be able to perform a radiator repair. However, replacement of the radiator may be required. Even with a total radiator replacement, the cost of the repair will not exceed $1,000 in most cases.

Repairing a bad water pump almost always requires the replacement of the water pump. This can be done for $300 to $400 if the water pump is on the outside of the engine, but the cost is likely to exceed $1,500 for water pumps mounted in the engine. Finally, a blown head gasket will typically be the most complex and expensive repair for coolant leaks. Replacing a blown head gasket requires fairly extensive engine teardown, and the labor costs will be quite high. It could cost you over $2,000 to replace the head gasket on your vehicle. Unfortunately, replacement is usually the only solution for a bad gasket.

Consequences Of Ignoring Coolant Leaks

You might be wondering whether a coolant leak even matters. Can’t you just keep driving with the leak? If the leak is minor, you can likely drive a short distance without any issues. Some people with very small leaks continue to drive for many miles and simply top off their coolant level when it gets low. However, if the leak is significant, you cannot drive with your vehicle in that condition.

Driving with a coolant leak can lead to your engine overheating. Allowing your engine to overheat can result in significant damage, such as a blown head gasket, warped cylinder heads, or a cracked engine block. These types of issues are detrimental to your engine, and they might require total engine replacement in some cases. If that happens, you might have a repair bill of $4,000 or more. Now you can see why you should never ignore a coolant leak!

The Bottom Line

Coolant leaks are not something that you can ignore, and there are a few common causes of leaks. Some of the most common culprits include a cracked radiator, bad radiator hoses, or water pump problems. Most of the time, you can track down the leak fairly easily. Sometimes, the leak is extremely obvious — such as in the case of a burst hose. Thankfully, most coolant leak repairs are not extremely expensive unless you have a blown head gasket.

Frequently Asked Questions

How much does a coolant leak cost to fix?

Now that you know how to fix a coolant leak, let’s discuss how much it will cost. Just how much does a coolant leak repair cost? Most coolant leaks can be repaired for less than $500. If you have a burst radiator hose, you can likely have that repaired for $150. Replacement of your radiator is likely to cost you $300 to $500, although it might cost a little more for high-end vehicles. A bad thermostat can usually be replaced for under $200, while a water pump replacement can go all the way up to $1,500 if the water pump is connected to the timing belt. Finally, repairing a blown head gasket is likely to be the most costly repair. You might pay $2,000 or more for this repair, and it is not something that you can ignore.

Can you drive a car with a coolant leak?

If you have a small leak, you can usually continue to drive the car for short distances without any problem. You should keep a close eye on your coolant level and make sure to keep it full. Allowing the coolant level to get too low could result in overheating. If you have a large coolant leak, you cannot drive the vehicle. Running the car with a low coolant level or without coolant altogether will quickly result in catastrophic damage to the engine.

What are the warning signs of a coolant leak?

In most cases, there are no warning signs of a coolant leak. Nothing will usually warn you before the leak begins. However, there are many symptoms that you might notice after the leak has started. You might see drops of coolant (ethylene glycol) under your car. You might also notice white smoke coming from your engine bay or exhaust system. Finally, a big telltale sign of a coolant leak is overheating. If you experience an overheating issue, you should head to an automotive repair shop right away to have the problem fixed.

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