Autotechiq
issues
Navigation

Hey, Why is My Car Leaking Coolant?

If you are short on time and want to fast-track the process to professional help, click Yes

Four common causes for a leaking coolant from the vehicle and their related parts.
The cooling system in a vehicle is a closed system and should maintain the same level without fail. Sometimes conditions happen that will cause the coolant to overheat to the point of overexpansion, and it will cause a leak. Other times the coolant in the cooling system is neglected, and the coolant becomes caustic to its vessel and creates a leak. And still, just over time and age, components of the cooling system degrade, and a leak will start. If you add coolant, something is wrong, and if left unattended will turn catastrophic.

Is Your Car Leaking Coolant?

The coolant leak is commonly caused by a crack in the radiator, the heater core, or the coolant reservoir. The radiator commonly cracks if it’s old or if it hits an object. The leak can also be caused by a loose coolant hose, a faulty water pump, or even a blown head gasket....read more

The coolant leak is commonly caused by a crack in the radiator, the heater core, or the coolant reservoir. The radiator commonly cracks if it’s old or if it hits an object. The leak can also be caused by a loose coolant hose, a faulty water pump, or even a blown head gasket.

Coolant is your vehicle's first protection against engine overheating; you're left vulnerable if it leaks. Checking your coolant levels regularly is a good practice since many leaks can strike unexpectedly. So, if you notice the levels dropping abnormally, something might be wrong.

Your cooling system requires routine maintenance. Coolant can turn acidic and eat away at gaskets and seals, causing dangerous leaks if neglected. In addition, factors such as temperature changes or simple wear can cause leaks.

While coolant does incredible things for your car, it is a toxic substance. It can poison animals and waterways if it leaks from a vehicle. In addition, because coolant gets hot when it's working, it can also scald someone standing near a leak.

Let's Get To The Bottom Of It!

  • Q: Do you have white smoke coming from the exhaust?
    You may also notice that the engine cranks long before starting. After the engine runs, you might...read more

    You may also notice that the engine cranks long before starting. After the engine runs, you might see a small puddle of coolant under the car.

    Coolant passages between the head gaskets connect an engine's combustion chamber to the valve chamber. These passages dissipate heat from the engine block and the heads. Engine overheating or acidic coolant can damage the head gasket. When these gaskets are compromised, gasses from combustion get into the coolant passages, causing the coolant to become superheated. Superheated coolant leads to the engine overheating and further wear on the gaskets. Coolant leaks into the engine's combustion chamber when the gaskets are badly damaged, which you'll notice as white smoke in the exhaust. That's the coolant burning with the vehicle's fuel.

  • Q: Do you smell a sweet smell coming from the air vents?
    You may also notice that the windows stay fogged even when the defroster is on or that the carpet...read more

    You may also notice that the windows stay fogged even when the defroster is on or that the carpet on the front passenger side floor is wet.

    Inside the air box in your vehicle's dash is the heater core. This circulates coolant so that your heater warms up the vehicle's interior. If the cooling system isn't maintained, the coolant turns acidic and can degrade the heater core. This can cause coolant to leak inside the vehicle. In addition, if coolant gets in the air box, it gets vaporized by air blowing over it and through your vents. You will notice this vaporized coolant as a sweet smell blowing through your heating and air conditioning vents.

  • Q: Does your coolant level keep getting low over time?
    You may also notice steam coming from under the hood or your engine is overheating. The co...read more

    You may also notice steam coming from under the hood or your engine is overheating.

    The coolant reservoir is the highest point of the cooling system and is filled with half air and half liquid coolant. When a leak in the reservoir occurs, the coolant won't be low in the tank until several heat and cool cycles force enough out. It is at this point that the low coolant is visible.

  • Q: Do you find a puddle of coolant under the vehicle after it has been parked overnight?
    You may also notice the "check engine" light is on or the "coolant temperature" gauge is running ...read more

    You may also notice the "check engine" light is on or the "coolant temperature" gauge is running in the red.

    The coolant hoses attach the engine cooling system to the radiator. Since they are made of rubber, they will become brittle over time and can crack, causing a leak. Flex from worn motor mounts can stretch the hoses as well. A band clamp attaches the hoses to the radiator or engine block. Wear over time and from temperature changes causes leaks. These leaks are most common after the vehicle cools when various components contract due to the temperature change. When your car is parked, it's cooling, and you will see the leak as evidence of this wear.

Find Professional Help

Please select your vehicle's brand and location so we can locate the best professional help for you
If you are a shop owner and sick of business directories that are based on the cost of repair, AutoTechIQ is for you. If your customers receive Digital Inspection results then AutoTechIQ is definitely for you. Check out the certification page or how to rank in your area.

Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Leaking radiator

The proof image shows the crusty buildup of coolant as proof that the radiator is leaking.

A customer dropped off their vehicle upon noticing some corrosion on the radiator. They thought the car's battery exploded, causing the problem.

The technician did not notice anything about the customer's concerns on the test drive.

During the vehicle health inspection, the mechanic noticed a lot of dried coolant on the upper tank of the radiator. The technician tested the battery and found nothing about the customer's concerns.

The technician used a cooling system pressure tester to pressurize the cooling system. They pumped up the pressure to the suggested rating on the radiator cap. Upon inspection, the technician found a small crack in the upper tank of the radiator that was causing it to leak coolant under pressure. The radiator requires replacement.

Does the issue look like this? if not accessible your shop will document it
Failing water pump

The proof image shows the crusty buildup of coolant leaking from the water pump.

A customer dropped off their vehicle after noticing a bunch of crusty, red buildup on the front of the engine. They thought they hit something on the road, and it splashed onto the engine.

The technician didn't notice anything about the customer's concerns on the test drive.

During the vehicle health inspection, the technician noticed that the coolant was a little low and confirmed a crusty buildup on the front of the engine.

The technician used a cooling system pressure tester to investigate where the coolant leak was. Next, they installed the tester on the radiator and pumped up the pressure to the rating on the radiator cap.

The shop verified that the coolant leaked from the water pump's weep hole. This confirmed that coolant was leaking from the seal at the water pump. As a result, the water pump will need to be replaced.

Does the issue look like this? if not accessible your shop will document it
Blown head gasket

The proof image shows a yellow block testing fluid, indicating that combustion gas is present in the cooling system. This proves that there is a blown head gasket.

A customer dropped off their vehicle concerned about seeing a lot of white smoke in the exhaust when starting the car. They also mentioned that the vehicle has been running much warmer than usual. Additionally, they remarked regularly adding coolant and not seeing it leaking from anywhere. They even checked the carpet underneath the dash for liquid and found it dry.

On the test drive, the technician noticed that the "check engine" light was on and that the vehicle did appear to idle rough. During the drive, the car almost reached the red line on the temperature gauge.

During the vehicle health inspection, the mechanic noticed low coolant. They did not see any external leaks on top or underneath the vehicle. Then they performed a vehicle code scan and found a code for an engine over temp condition. To further inspect the issue, the customer authorized the technician to use a coolant system pressure tester and pump up the pressure to the rating on the radiator cap.

Over time, the pressure fell slightly, but no external leaks were found. The technician then used a block tester filled with block testing fluid and inserted it in the radiator in place of the radiator cap. Next, they started the vehicle, and within 5 minutes, the block testing fluid turned from blue to yellow. This verified that the head gaskets were not sealing properly.

The technician recommended pulling the cylinder heads to investigate the coolant's damage to the cylinders, walls, and heads. A deeper examination will determine whether to recondition the heads and replace the head gaskets or if it is necessary to replace the engine.

Does the issue look like this? if not accessible your shop will document it
Heater core leaking

The proof image shows dried coolant collected on the air box, verifying that the heater core leaks.

A customer dropped off their vehicle after smelling a sweet smell inside the car. They didn't smell it underneath the hood. They suspected something in the cabin air filter.

The technician noticed a strong smell of coolant inside the vehicle on the test drive when the heater was on.

During the vehicle health inspection, the technician noted that the coolant was slightly low. The technician checked the cabin air filter, which appeared clean. No other notes were made relating to the customer's concern. To further investigate the issue, the customer approved additional tests.

The mechanic added a coolant pressure tester to the radiator and pumped it to the pressure rating on the radiator cap. They found no external leaks, and the pressure remains constant.

The technician then accessed the air box, where the heater core is located. They found coolant residue on the airbox. The airbox must be removed, and the heater core needs replacement.

Does the issue look like this? if not accessible your shop will document it
Coolant reservoir leaking

The proof image shows the leak in the coolant reservoir, causing the coolant to be low.

A customer dropped off their vehicle, stating it consumed too much coolant. Just that morning, they were checking their oil and saw that the coolant was down to the "add more" mark on the reservoir. The customer wondered if this coolant loss was average or if they were overfilling the coolant, making it leak out.

The technician did not notice anything about the customer's concerns on the test drive.

During the vehicle health inspection, the shop noticed a crusty, dried coolant buildup around the reservoir, and the coolant was at the minimum level. To further inspect this issue, the customer approved additional tests.

The mechanic topped off the coolant and installed a cooling system pressure tester on the reservoir lid. Next, they pressurized the cooling system to the pressure rating on the cap.

The technician then inspected for coolant leaks and found that the only leak was coming from the seam of the reservoir. So, the coolant reservoir must be replaced.

Does the issue look like this? if not accessible your shop will document it
Leaking coolant hose

The proof image shows coolant leaking from the pressurized radiator hose.

A customer dropped off their vehicle after noticing a puddle formation underneath the car overnight. This has been happening since the weather temperature decreased. The puddle is right underneath the front bumper on the driver's side. However, this doesn't happen when the vehicle is parked outside during the day.

The technician did not notice anything about the customer's concerns on the test drive.

During the vehicle health inspection, the shop detected low coolant levels in the car. To further investigate the issue, the customer approved additional tests.

A coolant system pressure tester is attached to where the radiator cap was and pumped up to the recommended pressure rating on the lid. The technician then sees a coolant leak between the radiator and the hose. Due to the softness of the radiator hoses, the shop recommends replacing the upper and lower radiator hoses and clamps.

Does the issue look like this? if not accessible your shop will document it

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

"Radiator Replacement" fixes "Radiator Leak"

The AutoTechIQ ranking for Safety, Cost Avoidance, and Environmental Impact is

Safetyi
env level
env level
Cost Avoidancei
env level
env level
Environmental Impacti
env level
env level
Hey, Why is My Car Leaking Coolant?
Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

Other things your auto repair shop might talk about:

Engine oil. Coolant leak fix. Car's engine. Coolant tank. Hose connection.