How to Properly Bleed a Car Cooling System by Yourself | ASC Blog (2023)

We know how difficult it is to get rid of all the air out of the cooling system with the help of a water pump or thermostat replacement. And if not executed precisely, it can damage your car’s engine eventually. Over time, the coolant system starts overheating due to the accumulation of air pockets. Wondering how you can bleed a car cooling system? Read ahead!

Drawing air from the cooling system can work wonders for your car. With a few easy steps, you can make the whole situation convenient and easy.

What is a Car Cooling System?

How to Properly Bleed a Car Cooling System by Yourself | ASC Blog (1)

One of the most crucial components of your car’s automobile engine is the cooling system. It has three chief functions:

  1. To get rid of heat from the engine.
  2. Maintaining the engine operating temperature.
  3. Bringing the engine to the correct operating temperature.

These functions play an essential role in maintaining the health of the engine. Your cooling system consists of six parts that assist with the efficient working of the car: Engine, Radiator, Water pump, Cooling fan, hoses and a thermostat.

(Video) How to Properly Bleed Engine Cooling System by yourself

When the engine is ignited, the fuel energy is converted into heat. This heat is later transferred to the coolant by the water pump and then into the engine. Sometimes this makes the coolant system extremely hot, making the engine depend on the radiator to stabilise the temperature.

What Causes Car Coolant to Boil?

Cooling systems in most cars depend on leak-proof circuits to pump antifreeze or coolant around the engine. When the air enters the sealed system, the blockage is formed by air pockets. It eventually causes the cooling system to overheat.

Bubbling or overheating is a sign of blockage in the cooling system. The most common cause can be a blown head gasket. In such a case, the air pressure is transferred to the cooling system from the cylinder heads. For proper guidance on maintaining your cooling system, seek help from a car service provider.

| Also Read: Car Cooling System – Parts, Working, and Common Issues |

How Do You Bleed a Car Cooling System?

How to Properly Bleed a Car Cooling System by Yourself | ASC Blog (2)

(Video) How to Drain, Fill & Bleed Radiator 05-10 Chrysler 300

Take a look at our simple guide on how to bleed a car cooling system manually without any special tool or equipment. Be extra cautious while handling the car cooling system as it tends to reach the boiling temperature. This method will take about 30 minutes to bleed the cooling system.

  1. Keep your antifreeze/coolant ready: The first and most essential step is to keep the liquid ready. Always use the coolant referred by your car manufacturer. It does not require much time to damage your engine with the wrong type of coolant. However, if you are unaware of which coolant to choose, get the help of an expert. Create a mixture with 50% concentrated coolant and 50% water. Read the instructions carefully for your coolant. Those living in cold places need to mix coolant correctly to avoid freezing in the engine. Opt for a Car Cooling System Repair if you notice any discrepancy.
  2. Jack up the front of the car: Many people ignore this step, but it makes a big difference if you jack up your vehicle. This step helps in getting rid of the air much more easily and quickly. To raise your car, use a floor jack or park the car on the steep hill with the front upward.
  3. Fill Coolant:When your car is raised, fill the coolant as much as possible. If there are air bleed valves, open them simultaneously while filling the coolant. Close the valves when the coolant starts flowing out. Since coolant is toxic, make sure it is not flowing on the floor, road etc. It is hazardous to the environment, and if any animal drinks it, can lead to death.
  4. Start the engine: Now that you have filled the coolant to the maximum, you should turn on the engine. While switching it on, the water pump will throw away some coolant from the radiator. It only happens when there is air inside the system.
  5. Turn the climate control heat: The next step is to turn the climate control heat to the maximum. This step differs from car to car. Many manufacturers build a valve that will prevent coolant from flowing inside the car’s thermal pack. However, this happens only if the climate control is set on cold.
  6. Rev the engine to 3000-4000rpm: For this step, you will need help from a friend. Ask the person to sit into the car and rev up the engine to 3000-4000 RPM. Make sure RPM is steady while you are working on it.
  7. Open the bleed valve carefully: While your friend is working on reviving the engine, you can loosen the air bleeding valves. Check if the coolant temperature is not too high, or it will be difficult to work with your car. Keep an eye on the coolant temperature and also whether it leaks or not.
  8. Refill coolant if required: Turn off the air bleeding valves. Let your engine be in an idle position and recheck. If required, refill the coolant. Put the radiator cap back when the coolant stays in place.
  9. Give your car a short spin: When you are confident about no more leaks, take your car out for a test drive. Be alert about the coolant temperature while you are driving the car. Overheating can blow your head gasket.
  10. Refill coolant again: If there is any temperature peak and the coolant level differs, make sure to refill the coolant. Check if there are any leaks. After this, you can leave your car for a few hours and take another test drive.

| Also Read: Full Car Service: What Does a Full Car Service include? |


How to Properly Bleed a Car Cooling System by Yourself | ASC Blog (3)

How long does it take to bleed air out of the cooling system?

Usually, it takes about 15-30 minutes, depending on the model and method you follow. It, however, takes 15-20 minutes to heat the engine and get rid of the coolant.

(Video) AutoZone Car Care: How to Bleed the Master Cylinder and Brake System

Will a cooling system bleed itself?

Your coolant system can bleed some between the overflow tank and thermostat. However, to properly bleed, you need to fill the coolant and run the car with the radiator cap off.

Do you bleed coolant with a car on or off?

You need to turn the water on and set it to flow lightly. Turn your car off to flush the radiator from the cooling system.

Bottom Line

How to Properly Bleed a Car Cooling System by Yourself | ASC Blog (4)

(Video) DIY - How to Bleed a Coolant System with Mishimoto Liquid Chill™ Synthetic Engine Coolant

If you follow these steps properly, there are no chances of any mistake. Make sure you do research and use the right product to keep your car cooling system healthy. If there are any problems or issues faced during the process, reread this guide and repeat it. We hope this guide about how do you bleed a car cooling system is beneficial and fruitful!

Tags: bleed a car cooling system, bleed cooling system, car cooling system, how do you bleed a car cooling system


How do you burp air out of a cooling system? ›

Burping (so named because of the noise made by the bubbles of coolant exiting the radiator filler neck) is done with the radiator cap removed on cars without a valve. You wait for the car to warm up so the thermostat opens, and then the pressure of the expanding coolant being heated drives the air out.

Do cars self bleed coolant? ›

Will a cooling system bleed itself? Your coolant system can bleed some between the overflow tank and thermostat. However, to properly bleed, you need to fill the coolant and run the car with the radiator cap off.

What happens if you don't bleed air out of coolant? ›

Over time, air can become trapped within your radiators, leading to cold spots and a less-than-optimal performance from your home heating devices. If you don't bleed your radiators, the issue will worsen over time.

How do you bleed a radiator for beginners? ›

Insert the radiator key into the bleed valve and place the cloth underneath to capture any water. Twist the radiator key anti-clockwise until you hear a hissing sound as the air escapes and close it again when water starts leaking from the valve. Tighten up the radiator valve again by turning the key clockwise.

Do you need to turn the water off to bleed a radiator? ›

Do You Bleed Your Radiators With The Heating On Or Off? You should always bleed your radiators when the heating is switched off and the system has cooled down, because bleeding radiators with hot water flowing through the system increases the risk of scalds and burns.

How do I know if I have air trapped in my cooling system? ›

Signs and symptoms of radiator airlock include: Overheating during normal driving. Heater not functioning correctly. Reduced performance.

How long does it take to get air out of cooling system? ›

Allow the engine to warm up and the thermostat to open so the temperature gauge reads normal. This can take 10 to 15 minutes, and be sure to keep topping up the funnel as required. Rev the engine between 2500 to 4000 rpm off and on for 5 minutes, this should allow the water pump to force air out of the system.

How do I know if my coolant is circulating? ›

Start your car's engine and allow it to idle. Look through the radiator filler neck to see if the coolant flows. At this time, it should not be flowing as your car has not reached the operating temperature to cause the thermostat to open. If you find the coolant is flowing, it means the thermostat valve is open.

How do you burp a coolant system without a funnel? ›

Just place a pan under the radiator to catch any coolant that might bubble out and do the same procedure as in my video. I usually don't fill the radiator all the way when I do this without a funnel so that it doesn't bubble out as much. When the fans kick on I fill the radiator the rest of the way and you're done.

Which radiator do you bleed first? ›

The radiator to bleed first

Making sure your central heating is switched off, you should start with a downstairs radiator that is the furthest away from your boiler. Work your way through the radiators getting closer to the boiler, then go upstairs and repeat the process.

What happens if you bleed a radiator too much? ›

You could risk scalding yourself with the hot air and hot water existing in the heating system. Even if you have had the heating turned off for a few hours, the radiators may not have fully cooled as the bleeding could result in the release of some very pressurised, very hot air.

How long does it take to fully bleed a radiator? ›

How long does it take to bleed a radiator? Typically, it only takes between 20 - 30 seconds to bleed a radiator. This can increase up to one minute, depending on the size of the radiator and the amount of air that needs to be bled.

Is it OK to just have water in your radiator? ›

Only Use Water In The Radiator In An Emergency

If it's really low or actually empty, you need to add fluid to your vehicle. While it's ideal to add a 50/50 mix of coolant and water (or a pre-mixed coolant), if you absolutely have to keep driving, you can add water to the radiator to get you to your destination.

How long does it take to burp a cooling system? ›

Replace Any Lost Coolant

For some vehicles, to burp the cooling system all you need to do is add coolant, start and let it run for 10 min, make sure the thermostat opens, which will burp air out, shut the vehicle off, let it cool down, and then top off the levels.

What is the most common cooling system problem? ›

One of the most common yet serious problems that develop in the cooling system is a radiator leak. A crack or leak from the radiator can lead to significant loss of coolant or antifreeze. Without these fluids present in the cooling system, air bubbles start to develop.

What draws cool air through the radiator? ›

Fan: The fan draws air through the radiator to assist in heat transfer. Water Pump: The water pump is considered the 'heart' of the cooling system and is usually located on the front of the cylinder block.

Does opening radiator cap let air in? ›

Removing the radiator cap does not let air into the engine. Taking the cap off while the engine is running is common (basically necessary) practice when replacing coolant.

What causes airlock in car cooling system? ›

Causes of Trapped Air in Cooling System

If the radiator cap fails, coolant can escape and let in air. This leads to trapped air in the cooling system. Here are some other causes of trapped air in the cooling system: Blown head gasket.

Will radiator pull coolant from reservoir? ›

To release pressure, the radiator cap allows some coolant to escape out, stored in the reservoir. This excess coolant stays here until the system cools down enough to create negative pressure and draw the excess coolant from the reservoir back into circulation.

What else can I use to bleed a radiator? ›

Alternative radiator bleeding methods

The most popular alternative to a radiator key is by using a flat head screwdriver. Most modern radiators manufactured over the last 5 - 10 years will have a small indent allowing for a flat head screwdriver to be inserted into the bleed plug.

Can you bleed a radiator with pliers? ›

You could use an Allen key, spanners or a plier to grip and twist the nut for an effective radiator bleed.

Why is my coolant reservoir boiling and overflowing? ›

Boiling coolant can indicate that your car's coolant level is too low. Good car maintenance requires a car owner to flush and replace the old coolant every two years or 30,000 miles. Low coolant levels also lead to decreased overall performance. You might experience lower fuel efficiency and a failing heating system.

How do you bleed a radiator without a bleeder? ›

For radiators with a slotted bleed screw, a simple screwdriver represents an ideal alternative to a bleed key. Just insert the screwdriver into the slot and turn it in a counter-clockwise direction to bleed the radiator.

What happens if you bleed a radiator with the heating on? ›

If you bleed a radiator with no trapped air inside you risk your boiler pressure dropping too low and your whole heating system failing - not what you want. You might be thinking, 'do you bleed a radiator with the heating on or off' - the answer is off, definitely off.

How can I flush my coolant without a machine? ›

To flush with water and remove any leftover residue from the old coolant/antifreeze, top up the radiator with clean water using a hose, and replace the radiator cap. Then, start the engine and leave it running for 15 minutes.

Which radiator to bleed first? ›

If your home has 2 floors you should begin bleeding the downstairs radiators first. It's also advisable to start with the radiator which is furthest away from the boiler. Once you've bled all the downstairs radiators you move on to the upstairs, again beginning with the radiator which is furthest from the boiler.

What happens if you let too much water out of a radiator? ›

Baird warns that letting out too much water is likely to introduce fresh water into the system, which can make the situation worse as fresh water contains a lot of air. He adds: “Some people also think if a radiator is cold on the bottom but hot at the top then it needs to be bled.

How long does it take to get air out of coolant system? ›

This can take 10 to 15 minutes, and be sure to keep topping up the funnel as required. Rev the engine between 2500 to 4000 rpm off and on for 5 minutes, this should allow the water pump to force air out of the system.


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