Does the Car Need to Be Running When Adding Coolant?

Coolant maintains a steady temperature in your vehicle’s engine by circulating through it and removing excess heat. Therefore, it might seem like the car needs to be running when adding coolant; however, that isn’t the case.

Your car should not be running when adding coolant. If the engine is hot, you could burn yourself or fill the wrong amount of coolant. A hot engine could make the coolant expand, so make sure your engine is off and cool and your car is in neutral before you begin.

In the rest of this article, I will explain why you shouldn’t add coolant when the car is running, what to do after adding coolant, and give you step-by-step instructions on how to add coolant to your car.

Why Shouldn’t Your Car Be Running When Adding Coolant?

There are several safety reasons why your car shouldn’t be running when adding coolant, including dealing with hot car parts.

Your car shouldn’t be running when adding coolant because a hot engine will make the coolant expand, which messes up the level reading. This might lead you to add the wrong amount of coolant, which could corrode your car’s engine cooling system.

A hot radiator could also burn you, so it’s vital to make sure your engine is cool before you begin.

To fill in the coolant, you will need to remove the radiator cap and open the coolant reservoir. Most radiator caps come with a warning label that warns against touching them when the engine is still hot. That’s why most car mechanics recommend that you wait at least 15-30 minutes for your engine to cool down before filling in the coolant.

Should I Run My Car After Adding Coolant?

You should run your car after adding coolant for a few minutes while you check for leaks underneath. This gets rid of air bubbles in the cooling system. After that, switch off the car and top up the coolant if necessary. Run the car again for a few minutes and check for leaks.

When you add coolant, you need to make sure it’s circulated through the engine, and there are no air bubbles in the system. Running the car flushes out air bubbles and distributes the coolant evenly through the engine. While doing this, you can also check beneath your car to make sure the coolant isn’t leaking and the drain plug is tightly shut.

How to Add Coolant to Your Car

Adding coolant to your car on your own can save you a lot of money in expensive car maintenance sessions. Although it might seem intimidating, adding coolant is fairly easy.

To add coolant to your car, follow these steps:

  1. You first need to make sure your engine is cool.
  2. Open the coolant reservoir and the radiator to check the old coolant and drain it if it’s too old or contaminated.
  3. After that, you can fill in the new coolant.

You can check out this YouTube video by Engineering Explained to see how to add coolant to your car.

Take Your Car Outside and Switch It Off

Before you begin, you’ll need to make sure your car is set up properly. Here are a few steps to take before you begin.

  1. Make sure your car is outside, with enough light to see into the hood.
  2. Prop the car up on some jacks.
  3. Pop open the hood.
  4. Wait at least 15-30 minutes for the engine to cool down if you were using your car earlier.

Once your car is propped up and the engine has cooled down, you can begin.

Check the Color, Consistency, and Smell of the Coolant

Before adding the new coolant, you should check the old coolant’s color, consistency, and smell. This will tell you if you need to professionally flush your engine’s cooling system or if you can fill in new coolant on your own.

Clean coolant is supposed to be translucent and green or yellow in color. Some coolants also come in an orange, pink, or red color. However, if your coolant is brown and opaque, that’s a sign of contamination. To get rid of the contaminants, you will need to get the cooling system professionally flushed.

Other signs of contamination are:

  • A thick, sludge-like consistency.
  • Particulate matter in the coolant.
  • A nasty smell.

Drain the Old Coolant

You don’t have to drain the old coolant if you simply want to top it up. However, if it’s been a long time since you’ve changed your coolant, you might need to drain it before adding any new coolant.

Coolant is held in two places in the engine – the radiator and the coolant reservoir. You will need to check and drain both if the coolant is old.

  1. First, remove the radiator cap and rest it on top to stop contaminants from falling in.
  2. Place a bucket or container under your car, beneath the drain plug. The drain plug is usually found next to the radiator, under the car.
  3. Look for the drain plug underneath your car and remove it to let the old coolant dribble into the container.
  4. Move your bucket under the engine and remove the engine drain bolt. Removing the engine drain bolt allows any remaining coolant stuck in the engine to drain.
  5. Once the coolant has been drained, replug the engine drain bolt and the drain plug.
  6. Remove the coolant reservoir and empty it into your bucket.
  7. Make sure the reservoir is clean and put it back.

Once your old coolant has been drained and you’ve made sure there are no contaminants in the cooling system, you can begin filling in the new coolant.

Fill in New Coolant

After draining out the old coolant, it’s time to fill in the new coolant. Make sure the type of coolant you’re using matches the instructions given in your car’s user manual. Follow the steps below to fill in the new coolant:

  1. Fill in the coolant reservoir. This reservoir will have markings to show the minimum and maximum amount of coolant to fill. Add enough for the coolant level to be just before the maximum mark.
  2. Add coolant to the radiator. The radiator will have a marking inside the opening known as the fill line, which shows how much coolant to fill. Most cars require around 5 liters (1.3 gallons) of coolant to reach the fill line. Check your car’s user manual to find out the exact amount needed.

Run the Car

Your car shouldn’t be running while you perform the above steps. After you’ve filled in the coolant, leave the hood up and run your car for a few minutes. This will eliminate any air bubbles and residue in the cooling system and allow the coolant to circulate the system.

Top It Off

Once you’ve run the car, you can now check to see if you need to add more coolant. If the cooling system had a lot of air bubbles, you might need to add a little more coolant. Make sure you turn off your car and wait for it to cool down fully before doing this. Once you’ve refilled it, run your car again.

Final Thoughts

When adding coolant, you have to make sure your engine is off and cool to avoid burns and irregular level readings caused by heat. However, you should run the car for a few minutes after adding coolant to remove air bubbles and circulate the coolant.

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