Radiator: Drain & Refill, or Flush?
Most radiators today are small, made of light weight aluminum, and crammed so tightly between transmission & oil coolers and fan(s) that you can barely see it. The inside of the radiator is made up of a honeycomb of rows that sends the antifreeze on a long journey from left to right of the radiator. Air is forced through fins on the outside of the radiator to cool down the antifreeze inside.
The majority of the rust, dirt and sediment gets trapped at the bottom of the radiator. IF there is a problem with excessive sediment, (which is relatively rare unless your cooling system has been experiencing some internal corrosion or breakdown) heavy sediment will not be removed very well by "flushing kits".
The fine tubing inside the radiator prevents any high pressure action that you might be able to apply through the small opening of the neck at the top of the radiator.
And there are many "radiator flush" additives, but they can't be used in aluminum radiators (which all newer vehicles are equipped with), and can be harmfully abrasive to any type of radiator... and still not improve performance.
| The condition of a typical radiator and cooling system requires just a drain and refill every 2 years. You can run some water through it after draining & before refilling if you notice any significant debris in the old antifreeze you just drained. Then refill it with a 50/50 mix of new antifreeze and water. |