Car Leaking Antifreeze When Parked (Causes & Fixes)

Your car may overheat during summer and freeze in winter if it does not have enough antifreeze.

This lack of antifreeze might be a result of leaks. In this article, we will be looking at why you might notice your car leaking antifreeze when parked and how to fix this issue.

Here are some of the reasons why your car is leaking antifreeze when parked

1. Broken Heater Core

One of the major reasons why you might notice your car leaking antifreeze when parked is a broken heater core.

Whenever the heater in a car is switched on, the heater core transmits hot coolant to the engine, and the generated heat is then released into the car through the ventilation system.

If there is a problem with the vehicle’s heater core, there is a high chance that the antifreeze will leak under the vehicle’s passenger seat.

2. Hole in the Radiator

Another fault that might cause your car to leak antifreeze when parked is a hole in the radiator. Car engines are manufactured in such a way that they withstand extreme temperatures while operational.

This is because the engine generates and absorbs lots of heat. While driving, it is impossible to stop the gradual corrosion of some engine parts due to water in the car’s cooling system.

Antifreeze leaks can be easily spotted in these metal components of the engine’s cooling system, which has undergone corrosion with time due to poor maintenance or long usage.

A notable example is the corrosion of the radiator, which can cause the creation of holes that causes your car to leak antifreeze when parked.

As the cooling system of the car is operational and the radiator is being overused, the tubes become weaker, and holes are formed over time, resulting in leaks.

3. Bad Sealing Gasket

The primary function of the sealing gasket is to seal between the coolant tank and the radiator. With time these gaskets wear out, which might be the cause of your car leaking antifreeze when parked.

4. Leaking Radiator Cap

Leaking Radiator Cap

Despite its small size, the radiator cap plays an important role in the car. Excess water pressure is inside the radiator, and the radiator cap makes sure the seal is tight, regardless of the pressure.

The Radiator Cap helps the cooling system function correctly by ensuring essential maintenance to the proper pressure.

However, with time, the seal on the radiator cap starts to degrade, leading to the escape of coolant as the springs wear. This might be the cause of your car leaking antifreeze when parked.

5. Bad Hoses

The radiator is connected to the engine’s cooling system through a variety of hoses. As the hoses become older, it tends to become hard and stiff, leading to cracks. These cracks are the cause of your car leaking antifreeze when parked.

An antifreeze leak may occur from the hoses attached to the water pump, the radiator, or the heater core.

6. Bad Water Pump

The primary function of the water pump is to ensure that there is appropriate coolant circulation in the entire system.

The water pump can the found in the bottom portion of the engine very close to the belt drive. The pump is connected to the lower house of the radiator.

Over time the connection of the water pump to the radiators may become loose or corrode. It may also undergo external damages due to various causes. This will lead to your car leaking antifreeze when parked in either case.

If the water pump cannot completely circulate the coolant across the cooling system, it may lead to the overheating of the engine.

7. Head Gasket Is Blown

The head gasket plays an essential role in the effective functioning of the vehicle’s engine. Though the impact of a blown head gasket won’t be felt immediately,

The primary function of the head gasket is to regulate a wide range of temperatures for the engine. The head gasket also survives excess pressure produced by the engine at both high and low pressures.

It is located in between the head cylinder and the engine block. If the Head Gasket is Blown, it might cause your car to leak antifreeze when parked.

If this occurs, it will be impossible for the head gasket to separate the coolant from the engine oil, which may damage the engine.

A blown gasket can lead to the leakage of antifreeze, resulting in a decrease in coolant level. Insufficient coolant will make it impossible for the cooling system to effectively cool the engine, leading to its failure.

8. Faulty Expansion Tank

The primary function of the expansion tank is to supply antifreeze to the radiator. It looks like a plastic container and is located beside the engine.

The expansion tank is connected to the radiator through a rubber hose. Coolant is transferred into the tank through the radiator when the engine heats up or cools down.

As this process continues over time, the expansion of the tank tends to weaken and wear down, as well as other components it is connected to.

This can lead to breaking the tank’s plastic, resulting in leakage of coolant. A bad or leaking coolant tank could also result in antifreeze leakage.

9. Malfunctioning Intake Manifold Gasket

If your Intake Manifold Gasket has a problem, it can cause your car to leak antifreeze when parked. This leak can result from a faulty gasket in the intake manifold of the vehicle.

This problem should be fixed immediately it is discovered to avoid damages to your vehicle’s engine.

Also Read: Power Steering Fluid Leak (Causes & Repair)

How to fix a Car Leaking Antifreeze When Parked

Car Leaking Antifreeze When Parked

The first step to fix a car leaking antifreeze when parked is to identify the exact location of the leak’s source. It is impossible to fix an antifreeze leak without locating the exact source.

Below are common methods that can be used to identify, locate the source, and fix the leak:

1. Fix Radiator Leak

An easy way to repair a radiator leakage is by installing a cooling system sealer. This sealer can prevent fluid leakage if the leak is not extensive or severe.

However, there may need to dismantle the radiator and invite a radiator expert to repair for severe leaks prompted by serious radiator damage.

2. Replace a Cracked or Punctured Coolant Reservoir

Fixing a puncture or crack in the Coolant Reservoir is more straightforward. You just need to get a silicone adhesive and place it on the portion of the reservoir that is damaged.

However, if the puncture or crack is extensive or severe, you might need to replace the tank immediately.

To change the spoilt coolant reservoir, firstly, you have to remove the hoses that connect the reservoir to the pressure of the coolant.

After that, remove the electrical connector and the mounting bolts. Finally, link the coolant hoses and electrical connector to the reservoir.

3. Replace Damaged Heater Core

Upon investigating the cause of the leakage and determining that it is due to a damaged heater core, changing and installing a new heater core is the best course of action.

It is advisable to make the replacement with the same type of heater core. Nevertheless, an ideal heater core must be made from aluminum and its heating core of copper. These materials last long as they are extremely durable.

4. Damaged Water Pump

If the cause of the leak is a damaged water pump, then the only way to fix this is to replace it with a new one. You need to buy a brand new pump or a remanufactured model to do this.

Here are some steps to follow if you want to change your car water pump:

  1. Remove the components of the belt drive in the engine.
  2. Remove the damaged hose connected to the water pump
  3. Loose and remove the bolts of the spoilt water pump.
  4. Install the new water pump. Use sealant for the connectors if necessary.
  5. Install the bolts by screwing them in until they are tight.
  6. Finally, Link the hose to the water pump.

Additionally, you might need to examine another component that makes up the cooling system to know if the leakage caused other damages.

Check out this video for a detailed guide

5. Seal Cracked Hose

A quick solution to a leaking cracked hose, if noticed, is to use repair tapes or rubber cement to seal the crack or holes. However, if the hose does not have a crack or hole but is leaking, you might need to put more tension on the clamp on the hose.

If the crack in the hose is severe and the leak is much, a quick remedy is to cut out the damaged parts. Loose the bolts from the new coupler and fix the cut ends of the hose to the clamp’s mender.

Also Read: Freeze Plug Leak (Causes & Fix)

Frequently Asked Questions About Car Leaking Oil When Parked

How Do I Find Out Where My Coolant Is Leaking From?

To identify a coolant leak in your car, first, scan the under of the car for coolant puddles. If you discover any, this might mean that fluid is leaking from your car’s cooling system. Examine the under of the hood while the engine is running to check if there is any leaking fluid. Simple track the fluid back to the source if you find any.

Why Is My Car Leaking Antifreeze but Not Overheating?

Your car may have an internal coolant leak, an external coolant leak, or a leaky radiator cap. You are advised to attend to this problem as quickly as possible because the longer it lingers, the higher the repair cost.

Can You Drive Your Car When It’s Leaking Antifreeze?

If your car is leaking antifreeze, your car is likely to overheat, which can cause a major problem to the engine. Quickly call an expert to examine and repair the car if you discover any fluid leak.


A car leaking antifreeze when parked in a garage means that there is a problem with its cooling system.

Different components make up the engine’s cooling system, and if any of the parts fail, the engine might develop issues.

A leak of antifreeze in the car can be caused by a crack or hole in the hose, a faulty water pump, a spoilt radiator, a bad radiator cap, or a damaged head gasket.

It is important you fix any of these issues immediately discovered because if you don’t, it might lead to more damages to your engine, which can be very costly to fix.

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