How Long To Wait To Add Coolant? Technical Opinion

How long to wait to add coolant depends on how hot the coolant in the car has become. The typical wait time is 20 – 30 minutes after switching off the engine.

This question is essential, especially if your vehicle experiences overheating, which can damage the engine or harm you.

As a result, we have created this guide post on how long to wait for the engine to cool down before adding coolant. We hope to provide a sum guide and answer some of your most-asked questions in this regard.

how long for coolant to cool down

 How Long To Wait To Add Coolant?

After a long drive, waiting a little before adding a new coolant to your car is advisable.

How long to let the engine cool before adding coolant depends on how hot the engine is and the circumstance that calls for a coolant top-off.

For instance, if you just drove under normal conditions and realized your vehicle needs coolants. You must wait between 20 to 30 minutes before adding coolant to the car. It allows the engine to cool down properly.

If your vehicle is experiencing overheating, then adding antifreeze could be necessary. However, you do not jump into adding coolant to a hot engine just like that. It is best to wait an hour or more for the engine to cool down properly.

You might wonder how I can know when my engine is cool enough to add more coolant. You can monitor the engine’s temperature through the temperature gauge.

Is It Ok To Add Coolant When Engine Is Hot?

Adding coolant to the engine when the engine is hot is not safe. Instead, exercise patience and wait for it to cool.

Adding engine coolant when it is extremely hot could cause severe damage to engine parts.

When coolants are added to the engine, there is a sudden change in temperature within the engine part. Although the engine might cool down, it could cause severe cracks in metal parts.

When cracks are in engine parts, it creates room for breakages, leaks, and more. Even if you are in a hurry, you must exercise patience regarding an overheating engine. 

Reasons for Cooling Engine before Adding Coolant

When you are faced with an overheating engine, there are certain things you need to know before taking any step.

Firstly, much pressure is built up when the engine is extremely hot. The higher the heat in the engine, the more the pressure in the engine. The heating typically creates this pressure up of fluids present in the vehicle.

As a result of these pressures in the vehicle, it is not advisable to open any cap in the engine that gives access to any fluid, including the radiator or coolant reservoir cap. If you decide to open the cap, you risk getting a severe burn from hot liquid and vapor pushed because of the built-in pressure.

As the engine cools down, so does the pressure in the engine reduce? You will have to wait until the pressure has decreased before it is safe to open the cap.

Also, waiting for the engine to cool before adding coolants adding coolant to hot carwill grant you time to observe for further damages. You can check for coolant leaks or other damages during the cooling period.

What Happens If You Add Coolant To Hot Car?

Besides having severe burns, if you attempt to add coolant to a hot car, you can also damage your engine. You could also damage the radiator and other parts of the vehicle.

The engine comprises majorly metal parts, so it conducts heat faster. When there is a sudden change in the temperature within the engine, thermal shock produces cracks in parts of the engine.

Coolants will circulate when you add coolant to the engine when it is still very hot. When rapidly cooling the engine, the engine parts will crack up. These cracks become more significant as time passes, allowing for leaks, contamination, and other damages.

How To Cool Down Car Engine Fast?

If you find yourself in a situation where your engine is overheating, there are certain things you could do to cool the engine faster. They include the following.

Cooling down car before adding coolant YouTube

1. Park and open the trunk 

When you see the temperature gauge slowly moving to red, at this point, you need to park your vehicle immediately as soon as you can park your car in a safe space. It allows cool air from the environment to assist in cooling the engine.

2. Turn off the Air Conditioner

Immediately turn off the air conditioner and leave the car to sit. Your vehicle’s AC is known to put a strain on the engine. It is because the engine powers the AC through the serpentine belt, which also powers other significant components. 

3. Turn on the heater

If the temperature gauge still shows that the engine is still overheated, this shows there is a lot of pressure in the engine. One way to release these pressures is by turning on the heater. The heater directs the heat away from the engine to the cabin.

When you do this, the heat in the vehicle will increase, so you should step out of the car. Open the windows and allow the heat to escape.

4. Shift to neutral and rev the engine while at a standstill

Anyway, to quickly reduce the engine’s heat is by shifting the transmission to neutral. Try to rev the engine while still at a standstill. By doing this, the engine can take in cool air, reducing the engine’s temperature.

Once you notice that the engine has reduced in temperature, you can then go ahead to check the coolant level. If the coolant is low, fit for any form of leaks, and then go ahead to top off the coolant.

In addition, if you do not have coolants, you can always use water as a temporary solution. Always ensure that you have coolants or water in your vehicle, especially in the summer when your vehicle stands a high chance of engine overheating.


When your vehicle experiences overheating, every fluid boils up, creating pressure that could hurt you if the cap is opened. It is essential to know how long it takes for coolant to cool down, which we have been able to treat in this article.  

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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