Ford F-250: How to Flush Radiator

Changing the coolant in the radiator is a basic service that will keep an engine running at its best.

By Pizzaman711 - December 18, 2014

This article applies to the Ford F-250 and F-350 Super Duty (2005-2014).

The coolant in the F-250 or F-350 Super Duty's radiator needs to be changed regularly. When the coolant gets old, it loses its cooling properties which can lead to overheating issues. These overheating issues can eventually damage your motor, and the last thing you need is to have your engine overheat during a long haul. This article covers how to flush your radiator so that can you can always keep clean, fresh coolant running through the motor without having to pay a shop.

Materials Needed

  • Pump
  • Drain bucket
  • Rubber tubing
  • Socket set
  • Flathead screwdriver or similar tool
  • Distilled water


Don't attempt this job if the motor is hot. Allow the truck to sit for 4-5 hours before starting this process.

Step 1 - Drain old coolant

  1. Open the hood.
  2. Remove the radiator cap on the driver's side of the engine bay.
  3. Using your pump, remove as much fluid as you can from the reservoir and pump it into your drain bucket.
  4. Using a flathead screw driver or something similar, remove the splash guard covering the radiator from underneath to gain access to the radiator drain valve.
  5. Attach your rubber tubing to the drain valve port and then turn the port counter-clockwise to open it and allow the coolant to flow out.
  • Figure 1. Pry back splash guard to access radiator drain valve.
  • Figure 2. Radiator drain valve.

Step 2 - Flush coolant and clean the radiator

  1. Tighten the drain valve on the bottom of the radiator.
  2. Fill reservoir with distilled water. You should be adding roughly the same amount that came out.
  3. Re-install the reservoir cap.
  4. Turn the truck on and allow it to fully warm; once the fans kick on, allow it to run for 3-5 minutes to allow the water to circulate through the motor.
  5. Turn the engine off and allow it to fully cool.
  6. Open the drain valve on the radiator again and drain out all the water into the bucket.
  7. Once the water has finished draining, tighten the drain valve.
Figure 3. Drain the water into a bucket.

Step 3 - Fill coolant

Pro Tip

Now is the time to check all of the radiator hoses. If any of them are cracked or worn, replace them before adding coolant in the radiator.

  1. Fill the reservoir with new coolant. If you didn't buy premixed 50/50, make sure it's mixed properly.
  2. When the reservoir starts to get near the cold fill line, allow it to settle into the motor before adding more to make sure you don't overfill.
  3. Once the reservoir level is resting at the cold fill line, you're done with this job.
Figure 4. Fill the reservoir with coolant to the cold fill line.

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