Car Leaking Antifreeze When Parked? Causes & How To Fix

Has your car been leaking antifreeze when parked? It can be difficult to tell what could be causing this issue with symptoms or no other symptoms present (no overheating or overheating), so you might need to do some thorough checks before jumping to conclusions.

A failure to properly diagnose and fix this leak could degenerate into more serious issues later on.

In this post, we’ll be taking you through some of the major reasons why your car would leak antifreeze when it’s parked and ways you can rectify this.

car leaking antifreeze when parked

Causes of Antifreeze Leak

1. Broken Heater Core

A broken heater core is a common cause of antifreeze leaking from the engine. This can happen if the heat exchanger in your car’s heater core becomes cracked or breaks due to wear and tear.

When this happens, coolant will leak into your car’s cabin and onto the ground beneath it. If you notice a wet spot on your floorboards, this is a sign that you may have a broken heater core.

2. Hole in The Radiator

If your car is leaking antifreeze, you should check the radiator for damage. A hole in the radiator can cause this issue, which can be caused by road debris or rocks striking the underside of your vehicle and puncturing it.

This can lead to overheating and even engine failure, so if you notice a leak it’s important to get it repaired immediately. You can check out these bad radiator symptoms to get familiar with things you should be looking out for before committing to any changes or repairs.

3. Bad Sealing Gasket

A gasket is a rubber or plastic part that goes between two pieces of the engine to create a seal. If your car has a leaking gasket, coolant may leak into the area where it’s supposed to be contained. This could cause damage to your engine and other parts if left unaddressed.

4. Bad Hoses

If your car has ever had a leak of any kind, one of the first things to check is the hoses. Your vehicle probably has dozens of these rubber tubes, which connect fuel lines and coolant lines to various parts of the engine.

Hoses can become cracked or brittle over time, causing leaks that can lead to serious damage if left untreated.

5. Leaking Radiator Cap

Check your radiator cap if you notice an antifreeze leak. If it is cracked or damaged, replace it immediately!

If the radiator cap looks okay but there is still a leak, then the next step would be to check your cooling system pressure. The most common cause of antifreeze leaks is an old or faulty radiator cap.

6. Bad Water Pump

The water pump is in charge of circulating coolant through the engine, so if it fails or goes out, you’ll see a lot of problems. If you experience an overheating problem and notice that your radiator is empty or low on coolant, it’s likely that your water pump has failed.

7. Blown Head Gasket

A head gasket failure occurs when the thin layer of metal separating the engine block and cylinder head fails. When this happens, coolant can leak into the combustion chamber and cause overheating. The cooling system won’t be able to cool the engine down, which will ultimately lead to engine failure.

While a blown head gasket doesn’t necessarily mean that you need to replace your car, it’s still something you should get checked out as soon as possible.

8. Malfunctioning Intake Manifold Gasket

The intake manifold gasket is a very common cause of coolant leaks. The intake manifold gasket seals the engine head to the intake manifold. When this seal fails, coolant can leak into the cylinder heads, causing overheating and/or detonation.

If you park your car with no leaks and when you come out after parking, there’s antifreeze on your driveway or garage floor under your car, then you may have an issue with a malfunctioning intake manifold gasket.

9. Faulty Expansion Tank

The expansion tank is a reservoir that holds excess coolant. The expansion tank supplies the antifreeze to the radiator. It is the plastic container that is located beside the engine. It should be located in front of the radiator, and there will be either a pressure cap or a bleed screw on top.

The pressure cap allows coolant to expand when it gets hot, so you shouldn’t have any problems with this part of your car leaking antifreeze when parked, however, this can happen so, it is better to check if your expansion tank is faulty or not.

How to Fix Leaking Antifreeze Issue

1. Fixing A Radiator Leak

A radiator leak is caused by the radiator’s coolant leaking out, which in turn causes the engine to overheat. To fix a leaky radiator, apply a cooling system sealer and then drive until you reach operating temperature.

If this doesn’t solve your problem, or if you have severe leaks due to serious damage to your vehicle’s cooling system, it’s possible that you may need to replace your radiator entirely.

2. Fixing A Cracked Coolant Reservoir

Use a silicone sealer and apply it on and around the damaged part of the reservoir. If the crack or puncture is huge, you need to replace the whole coolant tank.

Remove the hoses connecting them to the coolant pressure sensor and engine block. Then remove all bolts that hold up this part of your car’s engine compartment together with its mounting bracket. You’ll also need to disconnect the electrical connector from its harness connector close by. After that reconnect your electrical connector to your new one.

3. Fixing A Damaged Heater Core

If your car has a leaking heater core, the best solution is to replace it with a new one. A good quality replacement should preferably be made of aluminum that has a copper heater core. This type is usually very durable and long-lasting.

4. Fixing A Damaged Water Pump

Remove the belt drive components of the engine. Carefully remove the hose connected to the damaged water pump, and unscrew all bolts that are holding it in place on your vehicle’s engine block (if not already done so).

Check all other components of your cooling system for any possible damages or corrosion, and replace them if necessary before installing a new water pump.

Carefully install a new water pump, taking care not to damage any wires or hoses during the installation process; make sure that its connectors are sealed with sealant before tightening them back into place (if needed). Then connect the hose to the water pump. After this process, your bad water pump should be fixed.

5. Fixing A Bad Hose

If the hoses are bad, you can replace them with compatible hoses that fit your car’s cooling system. If there is a small hole or crack in the hose, you can apply rubber cement or use hose repair tape around it. You can also tighten the hose clamp to stop any leaks coming from this area.

If serious leaks are coming from an area where no holes are visible, cut out the damaged section of tubing and remove its bolts from its couplers.

Attach the cut ends of your new hoses to these replacement couplers using clamps and tighten the connector until they’re secure enough for driving purposes without leaking antifreeze again.

Read: Symptoms of Rod Knock


We hope you found this guide helpful. If you’ve ever had to deal with a leaking car, then you know how frustrating this can be, this can be caused by a blown head gasket, faulty expansion tank, malfunctioning intake manifold gasket, bad water pump, leaking radiator cap, bad hoses, bad sealing gasket, hole in the radiator or a broken heater core.

It can take time and patience to find the source of the issue so that it can be fixed properly, but if you follow the steps listed here carefully and thoroughly then there is a good chance you’ll fix the issue completely.