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Any type of fluid leaking from your car is cause for concern. But a coolant leak is particularly troublesome because it can lead to a variety of serious problems, including overheating and internal engine damage.

It’s a good idea to become acquainted with the common signs of a coolant leak so that you can address the issue as soon as possible.

Common Signs of a Coolant Leak

Do you think your vehicle might have a coolant leak? If you notice one or more of the following symptoms, you might be right.

low coolant level
A low coolant level is one of the most common signs of a coolant leak.

Coolant Leaking Onto the Ground

One of the most obvious signs of a coolant leak is fluid pooled underneath your vehicle. Unlike engine oil and most other fluids, coolant comes in a variety of colors (green, orange, etc.). So, the pool of fluid could be one of many colors, depending on what type of coolant your vehicle uses. 

Low Coolant Level 

If your car’s coolant level is low, that means there’s a leak somewhere. The leak could be either external (leaking outside of the engine) or internal (leaking into the engine or automatic transmission cooler).

Before you conclude that the coolant is low, however, it’s a good idea to consult your owner’s manual to verify that you’re checking the level correctly. On some vehicles, checking the level in the reservoir might not yield an accurate reading.

Sweet Smell from the Engine Compartment

Coolant has a sweet odor, which you might smell emanating from the vehicle’s engine compartment if there’s a leak somewhere.

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Coolant Staining

Sometimes, a coolant leak won’t be significant enough to result in fluid pooling underneath the vehicle. Instead, the coolant will accumulate on various underhood components, potentially leaving stains. You’ll notice that the stains are the same color as the coolant in the cooling system. 


Ignoring a coolant leak can lead to a low coolant level and subsequent engine overheating. Allowing a vehicle to overheat even once can lead to costly engine problems, such as a blown head gasket or cracked cylinder head.

radiator leak
You might find the radiator leaking from its hose connections, seems, tanks, or core.


Where does coolant usually leak from?

A coolant leak can develop at any point in the cooling system. To determine the exact location of the leak, you (or your mechanic) will need to do some troubleshooting.

You’ll usually find the coolant leaking from one or more of the following locations:

1. Hoses: Any of the various coolant hoses found throughout the engine compartment can rupture, resulting in a leak. Loose hose clamps can also be the source of a leak.

2. Radiator: You might find the radiator leaking from its hose connections, seems, tanks, or core.

3. Water pump: It’s not uncommon for the water pump to develop a coolant leak from its shaft seal. The gasket (or seal) that seals the water pump to the engine can also leak.

4. Thermostat housing: A damaged thermostat housing or housing gasket (or seal) can cause a coolant leak.

5. Engine freeze plug: If one of the freeze plugs on the side of the engine block and/or cylinder head becomes corroded, it can cause a coolant leak.

6. Cylinder head gasket: A faulty head gasket can allow internal engine passages to leak coolant externally (outside of the engine) or internally (into the engine’s combustion chambers). The coolant can also enter the engine’s oil passages, resulting in coolant-oil intermix.

7. Cracked cylinder head or engine block: Much like a blown head gasket, a cracked cylinder head or engine block can result in internal or external coolant leaks, as well as coolant-oil intermix.

8. Heater core: If the heater core ruptures, you might notice coolant accumulating on the floor of the vehicle, underneath the dash.

9. Intake manifold gasket: On some vehicles, coolant runs through the intake manifold, and a faulty intake manifold gasket can cause a coolant leak.

Ruptured transmission cooler or oil cooler: Many vehicles have a transmission and/or oil cooler that can be located externally or inside of the radiator. If an internal-style cooler ruptures, coolant will enter the transmission fluid or engine oil, resulting in intermix that can damage internal components.

10. Coolant reservoir: Over time, the coolant reservoir can become brittle and develop cracks, resulting in coolant loss.

11. Radiator cap seal: The radiator cap has a seal that can eventually fail and develop leaks.

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How to Find a Coolant Leak

Sometimes, you can pinpoint a coolant leak with a simple visual inspection of the cooling system. If that doesn’t work, the next step is to perform a cooling system pressure test. As the name implies, the test involves using a special tool to pressurize the cooling system, making leaks more apparent.

The video below demonstrates how to pressure test a cooling system:

How do I fix a coolant leak?

To fix a coolant leak, you’ll first have to find the source of the leak (as outlined above), then replace the necessary component(s). Once the repairs have been made, the cooling system must be bled of air to prevent overheating.

Can you drive a car with a coolant leak?

You should not continue to drive a car that has a coolant leak. A coolant leak can lead to a low coolant level, potentially resulting in overheating and costly internal engine damage. That’s why it’s important to fix a coolant leak as soon as possible.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : DIY , Cooling System Tagged With :
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