10 Simple Steps On How To Put Coolant In Your Car (Detailed Guide)

It’s important to know how to add a coolant to your car so that your cooling system works well and you don’t have engine problems. It’s a simple job that, if done right, can keep your engine from getting too hot and save you money (or a trip to your local auto shop). This guide will tell you, among other things, how to add coolant to your car correctly.

To add coolant to your car, you need to use the right mixture, refill the car through the overflow tank, and check your engine for overheating problems after adding coolant. Some newer car models may need to have the cooling system vacuum-filled.

The following are steps you can employ to add coolant to your car:

  1. Turn off the car and let the engine cool.
  2. Check the radiator or coolant reservoir.
  3. Take out the coolant or radiator cap.
  4. Empty the old coolant (optional).
  5. Prepare the mixture for your coolant.
  6. Fill the reservoir with engine coolant.
  7. Change the thermostat and the radiator or coolant cap (recommended).
  8. Test the engine for overheating.
  9. Examine the engine coolant level.
  10. Look for any leaks.

Using the wrong mixture in your car’s cooling system can lead to sludge, rapid corrosion, and damage to the engine. These problems make your ride uncomfortable and make it hard to keep your car in good shape. Continue reading this article if you want to avoid these problems and save costs whenever you want to change your coolant.

10 Steps on How to Add Coolant to Your Car

  • Turn off the car and let the engine cool: Make sure the engine is all the way cool. Depending on the temperature and if the vehicle was driven, this might take about 30 minutes. To prevent severe scalding, keep your vehicle cool.
  • Look for the radiator or coolant reservoir: The coolant reservoir is a clear white container with a black metal screw-on lid and hoses that connect it to the radiator. Usually, it’s at the front of the engine and has a range crafted on its side. If you find it, it means you’ve already found the radiator, which is usually under the engine. Use your service manual to find out exactly where your radiator and fluid reservoir are.
  • Take out the coolant or radiator cap:  Find the radiator or coolant cap under the hood. These caps are oval-shaped. Modern radiator caps contain labels, making them simpler to view. Remove the radiator/coolant cap once you find it. Before proceeding, cool the radiator or coolant cap. If it is, do not open it because pressurized gas or scorching fluid can escape and burn you. To release pressure, loosen the radiator or reservoir cap if the engine is cool (don’t open the cap abruptly). Use a thick cloth to unscrew the cap for safety. Even with a cool engine, wear gloves and protective goggles to avoid damage. Pressing down while twisting loosens a tight radiator or coolant cap. A small rubber mat under the fabric can improve grip.
  • Empty the old coolant (optional): Most refills restore low coolant levels. Draining old coolant is rare unless it is polluted or has the wrong water-antifreeze ratio. For a thorough drain, follow these steps (and tips):

Use a jack stand to elevate and support the front of your vehicle. Place a big drain pan—an oil pan, disposable pail, or bucket—under the radiator and remove the radiator cap (or the pressure cap from the coolant tank).

Unscrew your car’s drain cock. Your car’s drain cock may be screw threads, quarter-turn twist, or quarter-turn-and-pull, so check your service manual. Worn drain cocks break more easily when unscrewed than new ones. Before draining engine coolant, buy a new drain cock from your local auto parts store.

Drain engine coolant by removing the radiator hose clamp and engine hose. Use slip-joint pliers to remove spring-style clamps from the neck. Purchasing these hose-clamp piers saves time and avoids injured knuckles, which are common with older automobiles. They simplify lower radiator clamp access and release.

After draining the coolant, reconnect the radiator pipe and replace the drain cock.

  • Prepare the mixture for your coolant.

Most online sources claim that antifreeze and coolant can be used in place of each other, but this is not true.  Antifreeze is one of the two things that are needed to make a coolant mixture. Coolant is made up of water and antifreeze. Both parts take in extra heat from the engine and release it through the radiator. But antifreeze mixed with coolant is stronger than antifreeze by itself.

You don’t have to mix your own coolant if you don’t want to. Large retail outlets or auto parts stores sell pre-mixed antifreeze solutions. Some car makers might want you to use a coolant with a longer shelf life, which your local auto shop might not have. If that is the case, ensure to buy it from a dealer instead of purchasing something cheaper that won’t work with your car.

  • Fill the reservoir with engine coolant.

Before adding coolant, check the maximum (MAX) and minimum (MIN) lines on the overflow tank or reservoir. These indicators show coolant levels. If the coolant level is low or near the MIN indication, add the coolant mixture you created previously to a few inches below the MAX or full marking on the coolant tank. If you’re pulled over, use diluted coolant or distilled water (if you are in a pinch).

Car coolant placement is disputed. Refill engine coolant through the coolant tank, not the radiator. However, older vehicles without an overflow tank can top off coolant via the radiator cap (provided the engine has already cooled down). If you have an older automobile, slowly fill the radiator with your coolant mixture to an inch below the radiator’s neck.

Note: Raising your vehicle while replacing engine coolant eliminates engine air pockets.

Use a funnel when filling your radiator with coolant, whether in the garage or on the road. This prevents coolant from spilling on you or the floor. Be careful; this chemical is hazardous.

  • Change the thermostat and the radiator or coolant cap (recommended).

Once the radiator or coolant tank is full, put the cap back on until you hear a click.  At this point, you should be done, but I recommend taking this extra step. Before adding coolant to your car’s engine, you should have already replaced the thermostat and radiator cap, and here’s why.

The thermostat is an essential part of your car’s cooling system. A broken thermostat is the second most common reason an engine overheats after a broken radiator fan. Even if you keep adding more engine coolant or flushing it out, your engine will continue to overheat if your thermostat doesn’t work properly.

The cap and the thermostat can be changed for less than $30. Unless the thermostat is buried, changing it yourself should take less than an hour. Inspect the other components of your vehicle’s cooling system, such as the blower fan, hoses, belts, and sensors, while you are at it but pay particular attention to the water pump. Ensure the latter is not broken and can get the engine coolant moving.

  • Test the engine for overheating.

After you’ve done the steps above, close the hood and start your car. Let your engine run until the dashboard heating/cooling gauge reaches the normal operating temperature, then start the overheating inspection. How long you have to wait after getting a refill varies.

If you had to add coolant after driving, how long it would take would depend on how fast you drove, how long you were on the road and the season. A quick trip to the nearest store that is open 24 hours a day would take about 20 to 30 minutes, while a pass on the highway at 65 mph would give your car at least an hour to rest. In cold weather, the time will be shorter and longer in warm climates.

Note: If your car’s engine gets too hot while you’re testing it, turn it off, let it cool down, and then check the temperature gauge, head gasket, or radiator. If you don’t know much about cars, have a professional mechanic look at it.

  • Examine the engine coolant level.

During the check for overheating, when the antifreeze mixture starts to move around in the car’s engine, more space opens up in the radiator. Still, it’s best to recheck the coolant level after you’ve driven your car around and let it cool down. This will help determine if you need to add more coolant mixture to the overflow tank.

It should be easy to add more coolant until the level reaches the top of the radiator or the hot mark on the coolant tank. However, some vehicles may require a specific method to let the air out, so check your service manual.

  • Look for any leaks.

When refilling the radiator with engine coolant, check for leaks. I prefer to check for leaks and kinks after completing the first stages in this list because new radiator fluid may not reveal leaks. When the engine is warmed up, the new coolant is more noticeable.

Even without leaks, the car may show indicators of low coolant after adding fluid. In this scenario, have a certified mechanic inspect all internal and external systems. These include finding the leak and any coolant routes surrounding the engine. Replace spongy, damaged, or bloated items.

Dispose of the waste engine coolant properly. Unless your sink drains into the sewer or wastewater system, don’t flush it. Instead, dump it into a screw-cap plastic container and take it to the nearest treatment plant or recycling facility. Ask your local government or car shop about coolant disposal. Never dispose of used coolant in storm drains or on your grass.

How to put AC engine coolant in a car

If you’re mechanically inclined, you can prepare your own antifreeze solution. Most cars have a 50:50 mix of antifreeze and water, but this could change to 70:30, depending on the ambient temperature. Still, the best and safest way to dilute concentrated coolant is to follow the manufacturer’s directions on the back of the bottle.

Mix the coolant and water properly in a clean bucket, but never use tap water. This will keep mineral deposits from forming inside the engine and the radiator. Consider your coolant protection level when checking your service manual for the right coolant mix. The coolant protection level can be found by using an antifreeze hydrometer to test the freezing and boiling points of your antifreeze.

If the exact antifreeze solution you require is in short supply, don’t settle for a universal coolant. Doing so can cause parts to break down early and void the warranty on the car. Not only that, but these universal coolants don’t always work with the metal alloys, gaskets, and seals in newer cars. This is one of the reasons why car manufacturers are so strict about how much coolant their cars need.

Frequently Asked Questions

Should the car be cold to add coolant?

It is advisable to wait until your car’s engine is cold or has sat for at least three hours. However, in most cases, the engine should be cool (or at most warm) before adding the coolant to the radiator. Never add coolant to the radiator while the engine temperature is high, as pressurized water may escape from the reservoir when the coolant cap is unscrewed. The hot, pressured water will likely burn you.

What if you use the wrong type of coolant?

Using the wrong engine coolant will damage the engine and internal cooling system components because it is chosen for compatibility with engine materials. Cast iron block engines need coolants with corrosion inhibitors. Aluminum blocks require a coolant with separate additives; thus, they cannot interchange.

Plasticized radiators won’t work either. Mixing coolants, especially non-OEM ones, can cause sludge and corrosion. The bottom line is that not using a coolant recommended by the manufacturer can cause engine issues and high vehicle costs.

Conclusion on How to put Coolant in Your Car 

In summary, the following are 10 steps on how to put coolant in your car engine:

  • Turn off the car, and let the engine cool.
  • Check the radiator or coolant reservoir.
  • Take out the coolant or radiator cap.
  • Empty the old coolant (optional).
  • Prepare the mixture for your coolant.
  • Fill the reservoir with engine coolant.
  • Change the thermostat and the radiator or coolant cap (recommended).
  • Test the engine for overheating.
  • Examine the engine coolant level.
  • Look for any leaks.

The details in this article and the directions in your service manual will make adding coolant to your car a breeze. You need to be aware of the coolant levels indicators in your car and how your engine fluids look and do an occasional radiator drain/flush. In return, you’ll get worry-free vehicle performance.