How To Burp Vehicle’s Coolant System? | Rx Mechanic (2023)

The coolant system in your vehicle may not work as it should, even when all related components are running fine. To your utter dismay, your cooling system may not adequately cool the engine even when there is enough coolant in the radiator. But what could be the cause?

This could be because of trapped air in the cooling system hindering the coolant from getting to the engine. Where the radiator works as it should, burping the coolant system will be the solution.

If you replaced or worked on any cooling system components like the radiator, water pump, radiator hoses, etc., there’s a chance that air gets into the system during the replacement. It will cause the cooling system to work poorly or display cracked cylinder head symptoms.

Here, Rxmechanic will walk you through a simplified process on how to burp a coolant system. At the end of this article, you may also know how to tell if the air is in the cooling system

Step By Step Process On How To Burp Coolant System

Before you spend hundreds of dollars on your local mechanic to fix this issue, see how the cooling system runs. Does it stay within the average operating temperature? Does it overheat or not get up to average operating temp? Now, let’s look at how to burp the radiator with a funnel.

How To Burp Vehicle’s Coolant System? | Rx Mechanic (1)

(Video) How to Bleed Air Out of Your Car's Cooling System - DIY Method

Items needed

  • 50/50 Antifreeze
  • Clean rag or towel
  • Spill-free funnel
  • Time and patience.

Step 1: Park your car

Park your vehicle on a level and strong pavement. Ensure your radiator and the overflow tank is at the appropriate level. If the engine is cold, the coolant level should be on the COLD mark. If the engine is hot, then the coolant should be at the HOT level.

Step 2: Insert the spill-free funnel

Remove the radiator cover and plug in the angled piece of the spill-free funnel. Then place the main piece of the funnel on it. Ensure you fix the connections properly, and there’s no leak. Check the funnel kit for instructions on how to connect it.

Step 3: Fill coolant on the reservoir

Pour coolant into the funnel and let it go above half. This is to avoid coolant spillage when you start the vehicle. Start the car and allow it to warm up. Once the engine gets to the average operating temperature, the thermostat activates, allowing the coolant to rise and fall as it opens and closes. The trapped air escapes as the coolant rises and falls.

Open the vehicle door and set the climate settings to heat or hot. Switch the fan/heat setting knob to the OFF position. Turn on the vehicle.

Step 4: Start the engine

Turn on the vehicle and allow it to run. Now, you need time and patience. Allow the engine to run at the average operating temperature so the thermostat will grant coolant passage to cool the engine. Once the thermostat opens, the coolant on the funnel will drop, and you’ll see air bubbles coming from the radiator. That is the trapped air getting out of the system.

(Video) How To "Burp" Cooling System (Andy’s Garage: Episode - 17)

Give it time to complete its course. Remember, the engine must undergo several cooling cycles for a complete system burp.

Allow the engine to run for 30 minutes to 1hour. If you notice air bubbles coming out, check the overflow tank and ensure there’s adequate coolant in it. If there’s no or low coolant in it, pour in coolant till it gets to the HOT mark. (This is because the engine is running hot now, so it shouldn’t be on the COLD level).

The air bubbles will stop once there’s no trapped air in the system.

Step 5: Finish

Now, remove the spill-free funnel following the instructions on the funnel kit and recycle the coolant into a container.

Tighten the radiator cap and clean any coolant spills around the area. Test-drive the vehicle. You should see a big difference in how the cooling system cools the engine. If your temperature gauge needle is still pointing north, check if the thermostat is still functioning as it should and replace it if necessary.


Q: How long does it take to burp the cooling system on a car?

Burping a car cooling system requires time and patience. Depending on the amount of air in the cooling system and your vehicle make and model, burping will take up to 30 minutes to 1 hour.

(Video) How To Purge Air Out of a Cooling System! [FREE and DIY Method]

However, it takes about 5 to 10 minutes for the engine to get to the average operating temperature. It’s this time that the thermostat will activate to grant coolant passage to the engine.

Q: How do you get airlock out of coolant?

First and foremost, airlocks are air bubbles in the cooling system that stop the adequate flow of coolant within the system. This may cause the system to overheat. Hence, it is essential to know how to burp a closed cooling system to get rid of airlocks.

Removing the airlock from the engine coolant requires the following steps;

Mix the coolant with water or get a 50/50 coolant mix and fill the radiator and the overflow until they are both filled.

Remove the radiator cover. Start the engine and allow it to run. Monitor the instrument cluster and ensure the temperature does not go higher than it should.

After some time, the coolant level will drop. You will observe air bubbles on the radiator, which shows the airlock is getting out. Once the air bubbles stop, the airlock has been evacuated from the system. Refill the radiator and replace the cap.

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

Q: How do you burp coolant without a radiator cap?

How to burp a cooling system without a radiator cap is the same way you do it from the radiator cap. But here, you’ll do it from the overflow tank.

Remove the overflow cover and switch the heater settings to max full. Fill the reservoir tank to the COLD mark. Start and allow the engine to idle for 30 to 45 minutes. The coolant will drop as the trapped air escapes from the cooling system.

Q: How do you burp a motorcycle radiator?

Burping a motorcycle radiator is pretty similar to a car cooling system.

Most coolants are entirely loaded and ready to use. Some come with a 50/50 mixture of coolant and distilled water. That way, you don’t have to add anything to it.

To burp a motorcycle radiator, pour coolant into the cycle radiator and gently shake the motorcycle. Then start the bike and throttle it several times to completely bleed the system. Check the fluid level one more time and top it off when necessary. Pour the coolant into the radiator, and cover the radiator cap. You’re ready to go.

Now, remember that this is necessary only for coolant-cooled bikes.

(Video) How to “BURP” Bleed Air Out of a Cars Cooling System - Easy DIY process for ALL makes

Final word

Airlocks can make a well-functioning system act as if it’s malfunctioning. Air pockets can accumulate over time in the cooling system lines and cause engine overheating if overlooked. Hence, it is essential to learn how to burp a coolant system.

You may wonder what happens if you don’t burp your cooling system when there’s a need for it. It will cause the engine to overheat, leading to severe engine damage. This article has provided all the information you need to burp a radiator.


How do you burp a car's 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.

Can a mechanic do a coolant flush? ›

Your mechanic will also use professional-grade solutions to eliminate any existing debris, dirt, sludge, rust, and buildup that your system may be holding. A mechanic will then finish the coolant flush by adding fresh antifreeze to your engine along with a conditioner that will keep it protected for longer.

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

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.

How do you pressurize a car's cooling system? ›

Generally, it attaches to the radiator where the radiator cap goes, and you pump it by hand until the pressure on the gauge matches the pressure that is written on top of the radiator cap. Typically on a modern vehicle this pressure is between 13 – 16 psi. Let the vehicle sit with this pressure for 20 – 30 minutes.

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

Signs and symptoms of radiator airlock include:
  1. Overheating during normal driving.
  2. Heater not functioning correctly.
  3. Reduced performance.
  4. Radiator leakage / losing coolant quickly.
Apr 6, 2021

How do you fix trapped air in cooling system? ›

How to Fix Trapped Air in Cooling System. First and foremost, check to see if there's a bleeder valve on your car's cooling system. Some cars are equipped with a special valve designed specifically for bleeding air from the system. This is the easiest fix for trapped air, involving nothing more than turning a valve.

How long should I wait to drive after refilling coolant? ›

If you've only popped out on a short drive in town, the radiator won't be all that hot at all, and should cool down within 20 to 30 minutes. However, if you've been gunning it on the motorway, you can expect to wait around an hour for the radiator to cool down enough for it to be safe to handle.

Do you have to pressurize coolant system? ›

Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block. Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.

How do you tell if your engine cooling system is blocked? ›

5 Symptoms Of A Clogged Or Bad Car Radiator
  1. Temperature Gauge Reading Higher Than Normal: The temperature gauge indicates the temperature of a car coolant. ...
  2. Radiator Leaking Coolant: ...
  3. Radiator Hose Troubles: ...
  4. Coolant Color Change: ...
  5. Radiator Fins Bent or Broken:
Jul 28, 2022

How do I unblock my engine cooling system? ›

Drain the coolant from your radiator by opening the drain valve on the bottom of your radiator. Next, drain the coolant from your engine block by opening the block drain also. Add the purchased radiator flush to the radiator and let the car run. Drain like the old coolant, and suddenly your car is clean and fresh.

How do you Untrap air from a radiator? ›

Hold the valve key to the radiator valve, with a cloth and turn anti-clockwise. This will provide a means for the air to escape and you should hear a hissing. You'll know when all the trapped air has been released when water starts to drip from the valve.

Can too much coolant damage your engine? ›

Coolant is a fluid that is added to your engine that helps prevent it from overheating. If your engine gets too far above its normal operating temperature, some serious damage can be caused and in the worst case scenario, cause an engine to seize and require that it be replaced.

Can coolant ruin an engine? ›

Any type of dirty fluid in your engine can lead to a major component failure. For example, dirty coolant can lead to an antifreeze leak, causing an overheated engine, and a blown head gasket. One of the reasons why most consumers put off car maintenance is not being able to find a qualified mechanic.

What happens if you put coolant in a hot engine? ›

Caution: Adding cold liquid to an engine that's hot can crack the engine block because the hot metal contracts sharply when the cold liquid hits it. If you must add liquid to an engine that's still warm (and I can't imagine why you should) always do so slowly with the engine running.

What happens if you don't burp radiator? ›

Over time, air can become trapped within your radiators, leading to cold spots and a less-than-optimal performance from your home heating devices.

How long does it take to burn coolant out of exhaust? ›

It may take a few days to a week to burn off all this fluid out of the exhaust. One of the quickest ways to burn off all the coolant quicker is to hold the throttle at about 2000 rpms when in park for about 10 to 15 minutes.

How long does it take for coolant to return to radiator? ›

To use, simply pour a bottle into the radiator with the engine off and then start the engine with the heater turned up all the way. Let it run for 15 or 20 minutes to circulate.

How long does it take to purge a radiator? ›

The average radiator should take no more than 20 to 30 seconds to bleed in full. This can vary with the size of the radiator and the amount of air trapped inside. Simply carry on bleeding the radiator until the hissing noise has stopped and water begins to run out of the bleed valve.

What does GREY smoke from exhaust mean? ›

Blue or Grey Smoke

If the smoke from the exhaust pipe is either grey or bluish-tinged, it generally means that your engine is burning oil inside the combustion chamber. Burning oil could be due to a number of causes, from leaky valve seals to bad piston rings.

What does white smoke from exhaust mean? ›

• White smoke from the exhaust: This could be steam caused by condensation in the exhaust pipe or a more serious issue caused by an engine coolant leak. Excessive amounts of white smoke could indicate head gasket failure.

Can coolant damage your radiator if its the wrong one? ›

Using the wrong engine coolant can gradually lead to corrosion and damage to the water pump, radiator, radiator hoses and cylinder gasket. This can lead to damage to the engine in the worst case.

How long does it take a mechanic to flush a radiator? ›

A trained mechanic can perform a radiator flush in about 30 minutes using a commercial coolant flush and fill machine. Without a machine, a radiator flush takes about two hours. You'll need to allow additional time for any other services performed at the same time, such as radiator leak repair or inspection.

Should the coolant reservoir be full? ›

“When the engine is cool, open your hood, and locate the coolant reservoir. The coolant level should be between the F(full) and L(low) marks on the side of the coolant reservoir.”

How do you get trapped air out of a radiator? ›

Hold the valve key to the radiator valve, with a cloth and turn anti-clockwise. This will provide a means for the air to escape and you should hear a hissing. You'll know when all the trapped air has been released when water starts to drip from the valve.

What happens if no air comes out when bleeding radiator? ›

If you don't have any water coming out of a radiator after bleeding, it means you could have something blocking the bleeder valve, the pressure is insufficient in your central heating system, or it could be something different.

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.


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