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How to Remove Overfilled Coolant (Step-by-Step)

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Last Updated on: 7th September 2023, 12:38 am

If the coolant level becomes too high, it can lead to a variety of problems.

If you notice the coolant level is too high, you first need to wait for the engine to cool down. Once the engine has cooled down, you can use a syringe or use the radiator drain valve to remove the overfilled coolant.

In this article, we’ll discuss how to remove overfilled coolant and what happens if you leave it overfilled.

person twisting a car coolant expansion tank

What to Do if You Overfill Your Coolant Reservoir

Follow the steps below if you notice your coolant is overfilled.

  1. Firstly you need to turn off the engine and allow it to cool down.
  2. Once the engine has cooled down, open the bonnet/hood and find the coolant reservoir.
  3. Then use a syringe to remove the excess coolant, alternatively you can use the drain plug on the radiator.

Remember that coolant fluid is toxic and can be harmful to the radiator so make sure you dispose of it correctly.

What Happens if Coolant Is Above the Max Line?

When coolant is above the maximum line it can cause multiple issues.

Excess coolant can lead to over-pressurisation of the coolant system leading to a cracked radiator and other issues. This could result in potentially serious engine damage and costly repairs.

It could also cause coolant to be forced out of the expansion tank or radiator cap which can also cause damage.

Can Overfilling Coolant Cause Overheating?

Overfilling the coolant system probably wont cause the engine to overheat in and of itself.

However, if overfilling coolant bursts the radiator or hoses and loses coolant it can result in an improper antifreeze to water ratio or low coolant, which could potentially lead to overheating.


Overfilling the coolant reservoir can lead to multiple problems, including a cracked radiator and engine damage. It’s important to regularly check the coolant level and take action if the level becomes too high.

Removing overfilled coolant is a relatively simple process, but it does require some care and attention. Be careful to dispose of the coolant properly since it’s toxic and harmful to the environment.

Can I drive with overfilled coolant?

It’s not recommended to drive with overfilled coolant as it could cause over-pressurisation of the cooling system and lead to coolant being expelled.

How high can you fill coolant?

You should fill up the ‘max’ line on the coolant fluid reservoir. Make sure the level is between the ‘min’ and ‘max’ lines, anything higher than the max line is classed as being overfilled and can cause issues.

  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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