How Long to Let Engine Cool Before Adding Coolant?

Antifreeze or coolant pulls out the excess heat from your engine. What if the coolant level is low? In that case, you may get an overheated engine. Therefore, refilling or adding coolant might be a must-do job. Here, you need to follow some tips and know some basic things before adding antifreeze.

For instance, You must wait to put the coolant on after driving the mower or vehicle. So, how long to let engine cool before adding coolant? If your vehicle engine is heated, you must wait a couple of hours. Sometimes, it’s better to wait overnight and then put in the coolant the following morning. If you drive for a while and get a partially heated engine, you must wait 30 to 60 minutes to let the engine cool.

Otherwise, it’ll be challenging to refill the coolant in a heated engine. You can’t even think of opening the reservoir cap. Let’s see why you should cool down the engine before adding coolant & what’s the best time.

Why Should I Cool My Engine Before Adding Coolant?

You should cool the engine before adding coolant for 2 reasons; a pressurised cooling system & a severe burn from the heated cap. Apart from that, if you add the antifreeze before normalising the engine, it might give you some adverse conditions. Most importantly, the coolant will fail to do its job if you put it in that condition.

Let’s see why you should only add coolant after cooling your engine.

Pressurised Cooling System

The first reason is the pressurised cooling system. The engine components will be heated when you drive your vehicle for a long time, or maybe a couple of hours. Eventually, the cooling system will be in pressurised condition. You don’t even dare to open the cap to refill the coolant.

Let’s say you open the cap and add the antifreeze. Unfortunately, the coolant system won’t utilise the fluid & water efficiently. That’s why you should never add coolant to a heated engine.

A Serious Burn

Another reason is the burning issue. Once your engine gets too heated, you can’t touch it. Remember, connect the reservoir and the cap to access the coolant. In that case, all the parts will have a high temperature. Once you touch them, the heated part might burn your fingers or touch your skin.

That’s a serious concern for everyone who works with changing engine fluid & coolant. 

When Should I Add Coolant To The Engine?

So, you know why you shouldn’t put the coolant in a heated engine. It’s time to learn when to add the coolant to the overheated/heated/neutral engine.

You can add the coolant three different times. They are:

• After 30 to 60 Minutes: You can add the coolant to your engine after 30 to 60 minutes of resting. That means you should let the heated engine cool down for 30 to 60 minutes after driving the car/vehicle for 1 hour or so. The engine will be heated less within that time, and you can add the coolant only after an hour.  
• After a Few Hours: If you drive your car for a couple of hours, the engine will be heated. In such a case, you must let the engine cool down for 3 to 4 hours; until the coolant system and the engine is cool. In winter, this time could be as long as 15 to 20 minutes. You’ll get a cool engine within a while to change the coolant.
• After a Night: In hot summer, you should keep the coolant within hours after driving for a long day. It’d be better to leave the engine overnight and change the coolant the following day. Your car engine will have enough time to cool down and be ready to change the coolant.

Benefits of Adding Coolant in Cold Engine

Adding coolant to a cold engine is always the best idea one can ever give you. You got the three particular benefits. Protect your skin/finger, avoid the pressurised coolant, and get the optimum coolant performance.

First comes the safety benefit. If you add the coolant to a cold engine, it’ll never burn your finger/skin. The engine will be in perfect condition, and you can avoid the heated one accordingly.

Another benefit would be to avoid the pressurised coolant. The engine gets heated when you drive the car for a very long time. As a result, the coolant tries to remove the extra heat. Eventually, the coolant will have a lot of inside pressure. If you try to remove or open the cap, it might burst. You can skip the pressurised engine if you add the coolant to a cold engine.

Finally, adding the coolant in a cold engine will give you the best coolant performance. At least the water & coolant will get enough time to start working. There’ll be no damaging issues since the heated engine may cause some difficulties.

People Also Asked (FAQ)

How to Cool A Heated Engine?

You can cool down the heated engine only by leaving it for hours. The engine must be off and parked for hours. The engine will cool down automatically; only you should park it in a cool area.

When Should You Add Coolant?

Morning is the best time for adding coolant. After driving the vehicle for a long time, you should leave it overnight. Then, change or refill the coolant the following day.

Closing Words

So, how long to let engine cool before adding coolant? You must let the engine cool for a few hours before adding coolant. Sometimes, the engine may be ready to get the coolant within 10 to 15 minutes (especially in winter).

In summer, or once your engine is too heated, you must wait a couple of hours and let it cool before adding coolant.