While adding Antifreeze should I run my vehicle?

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  • 1 month ago

    Coolant and not Antifreeze. I have Honda coolant "Type 2" that has corrosion inhibitors without silicates and is not over expensive. Coolant also has a high boiling point. One can turn the engine on and watch the flow or wait for bubbles from air pockets but after a minute or two it will get dangerously hot. Therefor I always check in bottles if the amount of fluid that came out, equals the amount that went in. Then you know scientifically and do not have to guess. The Service Manual may have directions for certain air bleed procedures. Personally I do have a plastic reserve tank that vents either fluid in or out with engine temperature difference. One can also just check the mark at the reserve and keep the radiator cap closed. It is a good practice to try to check the thermostat because some fluid may wear the alloy zinc and copper out and cause the thermostat to fall apart. When you can not look inside or take the thermostat out easily from the opening and inspect it for any damage, the fluid should flow slowly past it when cold. When streaming fast down the neck, then the spring dis-functions and leaves it already in open position. This is a common find and a cold engine damages itself. The stream being blocked initially is a second reason not to wait for air bubbles. There is hardly any flow. On the picture is the radiator cap with an air vent that is to be opened above it.

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  • 1 month ago

    Fill the radiator and reservoir with a 50/50 mix of antifreeze and water. Then start the motor and run it for 15 minutes with the radiator cap off to purge the air bubbles from the cooling system.

    Source(s): Mitsubishi Master Tech
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  • 1 month ago

    No. Wait until the engine is cold. Add coolant in the reservoir up to the "cold fill" line.

    • ron h
      Lv 7
      1 month agoReport

      He's not through after that. He'll need to recheck several times to be sure the system has purged the air.

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  • Poppy
    Lv 7
    1 month ago

    If engine was over heated, yes. If only at operation temperature, no. Radiators are not meant to be opened for this any longer, use the over flow jug to keep fluid level correct.

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  • 1 month ago

    If the engine is hot, absolutely you should idle the engine as you slowly add coolant. If the engine is cold, just pour it in until it's full, then check it by idling the engine to get the bubbles out.

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  • Anonymous
    1 month ago

    It TOTALLY DEPENDS on the AGE and MAKE of your car or truck....& how hot is the engine right now?  Also, is the radiator totally devoid of fluid - half full - nearly full?

    • Anon
      Lv 6
      1 month agoReport

      Running  engine  while  filling, if not over 1/4 hot, is ALWAYS the  best  way. 

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  • CB
    Lv 7
    1 month ago

    If you are just topping up then NO assuming it is a fairly modern automobile with a coolant overflow/reserve. You are just topping up the reserve on a cool engine as the radiator has drawn in all the overflow anti-freeze during the cool-down cycle and you are just topping up the reservoir.

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  • 1 month ago

    Depends on where you are adding it to. The radiator is a yes. The reservoir no.

    • Anon
      Lv 6
      1 month agoReport

      YES. Either case if very low. 

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  • 1 month ago

    Yes (presuming it's a cool engine) and leave it running for about 15 minutes to make sure you get all the air out.

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  • Satan
    Lv 7
    1 month ago

    No, there's no need and more chance of being scalded.

    • Anon
      Lv 6
      1 month agoReport

      Running Or  not running, if hot enough to "scald " it WILL the instant cap removed. 

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