How to Bleed Your Cars Cooling System (9 Easy Steps)

If your cooling system holds some air, it can create air pockets that prevent the coolant from flowing around the engine. Here's how to bleed the system to prevent this from happening

How To Bleed Your Cars Cooling System

Getting all the air out from your cooling system after a water pump or thermostat replacement can be really difficult.

Your engine could easily overheat, and it may actually damage your engine seriously if you are not doing it right either.

There are some steps that will make the whole situation much easier. Follow this step by step guide and get all the air out quickly and safely.

Different Methods of Bleeding the Car’s Cooling System

Fill Coolant (2)

There are actually two different methods of getting the air out from your cooling system.

Old Manual Method

The manual method is the old-style variant of bleeding the cooling system.

Some cars have one or more air bleed valves to get the air out from the system, and some cars don’t have this air bleed valve, which makes it a lot more difficult.

To do this method, you do not need any special tools, and you will get a step-to-step guide on how to do it later in the article.

Vacuum Method

The new method, which I use myself, is the vacuum method. You need a vacuum tool for this and compressed air (depending on the tool) to use this method.

However, this method creates a vacuum and sucks out all the air from the cooling system within seconds, and then fills all the vacuum space with the coolant. This is a really efficient method if you have the tool, and you will never have to worry about car cooling bleeding anymore. You will get a perfect result every time, and the process takes under a minute.

If you are interested in one of these tools, you can find one here on Amazon. Please note you need an air compressor for this tool.

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If you do not feel that it is necessary to buy one of these tools and do not want to go to a workshop to do it, it is also fine. This is the way I do it when I do not have access to a vacuum bleeder:

How to Bleed Your Cars Cooling System

This is a guide on how to manually bleed your car’s cooling system without any special tools. Remember always to be careful when it comes to car cooling systems because it will reach boiling temperatures.
It is much easier to do this if you are two people, so make sure to bring a friend! Follow these steps to bleed the coolant system easily:

Total Time: 30 minutes

Step 1: Get the Coolant Ready

Coolant Mix

The first step in this guide is to make sure your anti-freeze is ready. You should always use the correct coolant that is required by your manufacturer. The wrong type of coolant could damage your engine!
If you are not sure which coolant you should use, check your repair manual or contact your authorized dealer.
Generally, mix the coolant with 50% water and 50% coolant (if it is a concentrated anti-freeze coolant).
Always read the description of your coolant for the correct instructions. If you live in a cold country, you have to make sure that the coolant mix is correct. If your coolant freezes in your engine, it will destroy your engine.
RELATED: 10 Best Engine Antifreeze & Coolants

Step 2: Jack up the front of the car

Jack Up Car E1611338560184

A step that not many people do but get you a much better result is to raise the front of your vehicle first. With this method, you will get the air out of the car a lot easier, especially if your filling cap is at your radiator. If you have a car with an external expansion tank installed in the engine’s rear, this may not be necessary.
To raise the car’s front, you could either use a floor jack or put the car on a steep hill with the front upwards.
When raising your car with a floor jack, always also use Jack Stands to prevent any accidents.

Step 3: Fill Coolant to MAX

Fill Coolant

Now when the car front is raised, it’s time to fill your coolant as much as possible. If your engine has air bleed valves, open them simultaneously as you are adding the coolant. Close them when coolant is flowing out from them.
Anti-freeze is toxic, and you should always check that your coolant is not flowing down in any wells on your floor or the road. All coolant should be returned to your local environmental assessment. Keep in mind that if any animals drink the coolant, they can get very sick, leading to death. Use anti-freeze with care! When you have filled your coolant as much as possible, go to the next step

Step 4: Start the engine

Starting Car

You should now start your engine. The best way to do this is to get help from a friend. When you start your engine, the water pump could push out some coolant from the radiator if there is air inside the system. To prevent this, a tool like this installed on your radiator is preferred:

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Step 5: Turn the climate control heat to max

Heat Cabin 1 E1578916665204

After you have started your engine, you should now turn the climate control heat to MAX. It depends on the car, but many cars use a valve that will restrict the coolant from flowing inside the car’s thermal pack if the climate control is set to cold.
Other cars redirect the airflow and not the coolant flow, so this step will not make a difference with these cars. No matter which model you have, it’s an easy step to put your climate control to the MAX heat.

Step 6: Rev the engine to 3000-4000 rpm

Rpm Limit

Put your friend into the car and let him rev up your engine to around 3000-4000 RPM. This could cause the coolant to flow out of the radiator if you do not use the spill tool. Keep the RPMs steady while you are working in the system. Make sure that the coolant is not getting too hot while you work on it, though.

Step 7: Open Bleed Valves Carefully

Coolant Bleed Valve E1611338814623

While your friend is revving the engine slightly, you can now loosen the air bleeding valves. Ensure the coolant temperature is not too high as it will be dangerous to work with your car then. Be attentive to any coolant temperature peaks and coolant leaks at this point. Open the bleed valves carefully until it comes to water from them and then closes them. Do this a couple of times until it only comes coolant from them when you open them.

Step 8: Refill coolant if necessary

Fill Coolant

Close your air bleeding valves. Let your engine idle again and recheck and refill the coolant level and lower the front of your car. At this point, you should repeat these steps until you get heat inside the car and your coolant temperature reaches 90c and stays there. Put your radiator cap back. If your coolant temperature is now at 90c (work temperature) and you have heat inside your car, the air should now be gone from your vehicle. Warning: Hot coolant can cause damage to you if it’s not used with care.
RELATED: Low Engine Coolant – Is it Safe to Drive?

Step 9: Go for a test drive

Drive Car

You should now make sure that you can’t find any leaks after your repair. If it seems good, take your car out for a long test drive. Be very attentive about your coolant temperature during the test drive, and make sure the car does not start to overheat. Overheating can cause your head gasket to blow, and you really do not want that to happen. Check all the functions and the temperature of the climate control.

Step 10: Fill coolant again

Refill Coolant E1611338886692

If your test drive went well without any temperature peaks or other strange behaviors, open your hood and recheck your coolant level. Check for any coolant leaks.
After this, you can let your vehicle stand for a couple of hours, then take another test drive, do the same procedure and check for leaks and the coolant level.
After all these steps, your repair should now be successful. If there are any strange behaviors, repeat this guide or continue your troubleshooting.
RELATED: Can you use only water without any coolant in the radiator?

Supply:

  • A friend

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.