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Home / Symptoms / Radiator Leaking

Four common causes for a vehicle Radiator Leaking and their related parts.

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Have You Noticed a Leak In Your Vehicle's Radiator?

A radiator leak is commonly caused by a loose/broken radiator cap, damage in the radiator hose, internal chemical electrolysis, or a crack in the tank due to impact or wear. Also, note that a coolant reservoir leak can be commonly mistaken for a radiator leak.

Remember, promptly addressing a leaking radiator is an investment in your vehicle's longevity and peace of mind.

Watch out: This can result in overheating, engine damage, and unreliable performance. So, it's crucial not to overlook the bad signs and take prompt action. For example, if you notice coolant puddles or a decrease in your vehicle's coolant level, it indicates that the radiator fluid is seeping out. Ignoring these warnings can lead to costly repairs and inconvenience down the road.

The most common causes for a vehicle radiator leaking

The most common causes for the car’s radiator leaking:

Leaking coolant reservoir: The coolant reservoir is a container that stores coolant. If this container gets damaged or its seals or hoses fail, it'll allow coolant to leak out.
Faulty radiator cap: The radiator cap is supposed to hold up to 12 pounds per square inch (psi), but it can fail and only hold, say, less than 4 psi. This all means that the radiator won't hold up coolant as it should, and the cap must resist overflowing. However, since the cap was weak and loose, the coolant was overflowing and leaking.
Radiator tank leaking: The radiator is one of the most important cooling components in your vehicle. It works by sending cold coolant to the engine and receiving hot coolant in return. Then, it cools the hot coolant just received, starting the process over again. The radiator relies on seals and hoses to keep coolant moving inside the system. If the radiator gets damaged, worn, or faulty, it'll allow coolant to leak out.
Radiator chemical electrolysis: In this case, chemical electrolysis might be causing damage from the inside of the radiator and creating the pinhole. The pH level of the coolant commonly gets imbalanced, going beyond the normal range, and causing electrolysis.
Faulty head gasket: The head gasket is a "barrier" that sits in the eye of the combustion tornado, between the engine block and cylinder head. The main role of the gasket is to keep the coolant from touching the oil, making sure the engine has enough of both fluids without cross-contamination. However, if the head gasket fails, these fluids might escape the system and leak out.
Radiator hose leaking: The coolant goes through specific hoses leaving the radiator that directs it toward the engine, AC compressor, etc. If any of these hoses cracks, gets loose, or develops bad sealing, they'll allow coolant to leak out.

Frequently Asked Questions

Is the "low coolant" light active on the dashboard?

The coolant reservoir is like a container holding a specific coolant amount and returning it to the engine. But if the reservoir is damaged, the coolant leaks out. After the engine heats up, it needs the coolant back, but there won't be enough if the reservoir leaks. This can turn on a light on the dashboard showing a low coolant level.
Does the coolant reservoir keeps overflowing?

The radiator cap keeps the pressure inside the cooling system at a safe level. If the pressure gets too high, the radiator cap releases some of it to prevent damage to other cooling system parts. However, if the radiator cap cannot hold or release the pressure properly, the coolant will start coming out of the cap too soon. This can cause the coolant reservoir to overflow regularly.
Do you see a red, yellow, or green crust around the radiator hose ends?

The radiator hoses are like flexible tubes made of rubber. They connect to the radiator and the engine block through firm hose adapters. They carry the coolant from the engine to the radiator and back again. Over time, the rubber hoses can become stiff and fragile because they're made of rubber. Additionally, when the coolant becomes acidic, it gradually weakens the hoses from the inside. If you notice a coolant leak, it may be because the hoses start leaking at the connections between the fittings and the hose itself. You might see a dried, crusty material of a specific color, meaning that the coolant has been leaking.
Is the engine oil texture resembling a milkshake?

The head gasket is like a seal that connects the engine's head to its block. Its main job is to keep the coolant passages separate from the oil passages and the combustion chamber. However, the coolant can become acidic if the engine gets too hot or the cooling system wears out. This acidity and electrolysis can damage the head gasket and create leaks. As a result, the coolant can enter the cylinder and pass through the piston rings, eventually ending up in the crankcase where the engine oil is stored; this results in a mix of coolant and oil. When this happens, the engine oil looks milky, resembling a dark milkshake.
Are there pinhole leaks in the radiator?

The coolant must have a certain alkalinity level to stay healthy. However, as time goes by and the coolant gets used, it becomes more acidic. This acidity allows the coolant to conduct electricity. This creates a process called electrolysis, which can damage plastic and aluminum parts in the engine. As a result, these components start to wear out, and small holes, called pinhole leaks, can form.
Do you notice coolant puddles under your vehicle?

The radiator comprises two tanks on each end of the core. Its purpose is to allow coolant to flow from one tank through the core, into the other tank, and back to the engine. The radiator's core is typically made of aluminum or copper, while the tanks are made of plastic. A rubber seal between the core and the tanks is in place to keep them connected. However, as time passes and the radiator is used, this seal can become weak and brittle, eventually cracking. When this happens, it can lead to a leak underneath the vehicle.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Leaking radiator tank

The most common reason for a car’s coolant leaking is due to a radiator leak. The radiator is the "conversor" in your vehicle's cooling system that converts hot coolant into cold. This conversion happens because the radiator sends cold coolant into the engine; this coolant then heats up due to the engine's high temperature. Next, the now-hot coolant leaves the engine, returning to the radiator where it cools down again. The radiator relies on various seals, hoses, and protections to prevent coolant from leaking out. However, due to wear and damage, these seals can fail, allowing coolant to leak out.

Symptoms it causes: Apart from the coolant leak, you might notice engine overheating, smoke from the hood, burning oil smell, etc.
High risk of priority: The radiator is vital to keep your vehicle's engine from overheating. An overheating engine quickly damages various components and messes up the combustion process. In worst cases, the engine might overheat beyond safety limits and break down — or start a fire.

How exactly does the radiator start leaking?

Radiators are made to last close to a decade. However, they can wear out faster depending on driving conditions, accidents, misplacements, etc. Additionally, even though the radiator itself might not get cracks or damages, the connectors and sealings on it can become dry and damaged, allowing coolant to leak out. The most common reason a radiator leaks out is due to some kind of impact or accident in the vehicle's front, which is where the radiator sits.

Go safe: Ask for a mechanic to inspect your vehicle’s cooling system to investigate if the radiator is leaking due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the radiator to leak. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a leaking radiator service

A cooling system inspection is the most transparent process to understand why your vehicle’s radiator is leaking. This is because many components surrounding the radiator, coolant hoses, and engine can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a leaking radiator.

When the customer dropped off their vehicle, they mentioned noticing a red liquid puddle where they usually park.

During a test drive, the technician encountered no issues related to the customer's concern. However, during a vehicle health inspection, the technician noticed the coolant level was low.

To investigate further, the technician used a cooling system pressure tester. They connected the tester to the same place where the radiator cap goes and increased the pressure to 12 pounds per square inch (PSI), which is the rating of the radiator cap.

The technician discovered the radiator was leaking between the tank and the core through the test. As a result, the radiator will need to be replaced.

The radiator is leaking coolant, causing fluid loss, resulting in engine overheating.

In this case, the mechanic put the “Immediate Action” tag on the radiator.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for a vehicle Leaking Oil and their related parts.

Have You Noticed a Leak In Your Vehicle's Radiator?

The most common causes for a vehicle radiator leaking

Frequently Asked Questions

Is the "low coolant" light active on the dashboard?

Does the coolant reservoir keeps overflowing?

Do you see a red, yellow, or green crust around the radiator hose ends?

Is the engine oil texture resembling a milkshake?

Are there pinhole leaks in the radiator?

Do you notice coolant puddles under your vehicle?

Typical fixes to address the cause(s)

The most common cause: Leaking radiator tank

How exactly does the radiator start leaking?

Transparency example in a leaking radiator service

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