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Learn2 Flush a Car Radiator (continued)
Step 9: Bleed the system

P>It's probable that pockets of air will be in the cooling system after you've refilled the radiator. The system is self-bleeding when you follow these steps:

  • Start your engine, but leave the radiator cap off so the pressure doesn't build up.
  • Let the engine run until it reaches its operating temperature of about 190F (88C). This'll take about 15 minutes.
  • Turn on your heater and set the temperature control to hot. This will circulate the coolant and any air in the heater lines and core.
  • Check the level of the coolant. You may find that the level has gone down some. How did that happen? The air trapped in the radiator kept the level artificially high; when this air was released, it opened up more space in the radiator, and allowed more antifreeze into the system. Add more water and antifreeze, in the same 50/50 ratio, to fill the space left by the bled-out air.
  • As the air bleeds out, the coolant may bubble and spit from the opening on top of the radiator. Use caution--that coolant is hot.

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Step 1: Clean the radiator front and fan
Step 2: Place the drain pan
Step 3: Remove the radiator pressure cap
Step 4: Inspect the radiator pressure cap
Step 5: Inspect the clamps and the hoses
Step 6: Drain the radiator
Step 7: Rinse the radiator
Step 8: Add the coolant mixture
Step 9: Bleed the system
Step 10: Replace the radiator pressure cap
Step 11: Clean up


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