How to bleed antifreeze from the cooling circuit

Purge circuit and refrigeration through purges

Whenever we substitute the cooling system antifreeze necessary purge it completely. This process consists of removing all the air from inside the circuit, so that it is completely filled with liquid. If we don't, the engine won't cool down properly and will end up seriously damaged.

Bleeding antifreeze is a process relatively simple, but there are some notions that should be clear. The first and more important is that not all cars are bled the same way. There are three types of bleed system: through the expansion vessel or plug, through specific bleeders and through an automatic bleed system.

The second important notion is that we must have careful not to burn, because the antifreeze can splash. Since we will have to start the engine to bring it up to operating temperature, the antifreeze will be very hot. The third es que antifreeze is toxic, so you have to avoid getting it in your eyes. It never hurts to put on glasses and gloves when working on the car.

Bleeding through the expansion vessel or radiator cap

Bleed antifreeze through the expansion tank

This method is the simplest and is the one used on most cars. Once we have put the new fluid into the cooling system (also called cooling system), the air remaining in the circuit must be removed through the expansion vessel or plug. These are the steps:

  • Act quickly. starting the engine to get to the operating temperature. This will open the thermostat and the liquid will circulate all the way.
  • Put it heating to the maximum with the fan close to minimum, so that it also opens the secondary circuit.
  • You will see the air leave the cooling system little by little, at which point the antifreeze fluid suddenly drops. Every time you see this happen, add more trying not to go below the minimum at any time.
  • You will have finished purging when the air stops, but make sure the engine has been at its optimum operating temperature for a while. Then, close the expander vessel or the cap of the radiator.

If the radiator is not bled, the engine of your car will not refrigerate well and may end up overheating with consequent breakdowns. Many of them very expensive, such as the head gasket.

Types of antifreeze for the car
Related article:
Antifreeze for the car: what types are there and which can be mixed

Remove air from the system using bleeders

Purge circuit and refrigeration by purging hoses

There are cars that have antifreeze drains. on hoses and other parts. They are usually screw caps or keys that can be easily opened by hand or with a screwdriver. It is better to use them if your car has them, but if you cannot find them, you can also use the expansion tank or radiator cap. Follow the instructions above if this is your case.

If you use the purgers, the process is essentially the same:

  • Open them and start the engine to move the liquid throughout the circuit
  • Do not forget also turn on the heating at maximum with the fan close to minimum, so that its secondary antifreeze circuit opens.
  • Monitor the level of antifreeze so that it does not go below the minimum. Fill as it descends, just as it is done with the purge through the expansion vessel. Try not to wet anything you shouldn't, in How to clean the engine We tell you what the consequences can be if the liquid reaches what it shouldn't inside the opening. Antifreeze has low electrical conductivity, but it never hurts be cautious.
  • You will see that bubbles and air come out at intervals through the bleeders. Close them when you see that only liquid comes outBut be careful not to burn yourself.

Bubbles in coolant until purging is complete

antifreeze hose
Related article:
The car leaks antifreeze, what do I do?

Open vents when refilling with antifreeze

In some cars, such as certain Audi models, you have to leave the bleeders open when refilling the refrigeration system. This is how most of the air comes out with the engine off. In these cases, fill up until the liquid overflows through the drains. At which point you should close them. It's simple and you won't be able to burn yourself because everything will be cold. However, this does not exempt you from having to start the engine to warm it up and continue bleeding later.

Wear heat-insulating gloves when draining antifreeze

Keep in mind two tips if you have to use the purgers:

  • Wear gloves that insulate you well from the liquid if you see that you will have no choice but to wet your hand
  • If there are multiple traps, do not open more than you can control at the same time. If not, you will waste a lot of antifreeze, which is waste of money after all.

Automatic cooling system antifreeze purge

There are cars that are capable of purge antifreeze by themselves. In these cases, you have to know how to activate the purge system, because each brand is different. Look in your car's instructions to find out how to do this. In the following video you can see an example of how it is activated in a BMW:

If you want to be clear about everything related to this important part of your car, do not miss the article: The maintenance of our radiator. In it we explain to you from the way of clean the radiator and the entire circuit inside and outto what to do if you have leaks in your system. 

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      juan manuel said

    hello I have a peugeot 207 year 2011 and as a result of a crash I had to replace the radiator and when it comes to purging it it gets complicated. In this case, how should I do it? Thank you very much in advance.

         Diego said

      The same thing happens to me with the same car, the issue that remains to be seen is if it purges

           Marti said

        After purging it with the bottle it failed me again, then I took out the antifreeze I opened the radiator pipe I put a hose in one of the heating pipes I left it for a while to clean it well I put the antifreeze back in and now it works perfectly
        Quite a lot of grit came out

      David fernando said

    Does it take a long time for coolant to come out of the bleeder holes?

    I started my vehicle to purge it with the orifice open but after almost half an hour nothing happened.
    In fact, it doesn't feel like air is coming out.

    Should I wait more?

    Any suggestions?

      sergio said

    tutorial and support comments are appreciated. Thank you!!

      aide martinez said

    good afternoon I have a ford festive model 2000 and I need the base of the thermostat if I can get it and how do I get it how much is it worth thanks

      Hector said

    how to bleed my mercedes benz c230 from 2006 with 6 cylinders, someone who knows please help me