There are a few ways to vacuum a radiator, but the most common is to remove the screws that hold the cover in place and then pull the cover off. You can then use the vacuum cleaner to suck up any dust or dirt that may be hiding in the crevices of the radiator. Be sure to avoid getting the vacuum cleaner too close to the hot fins on the radiator, as this can damage it. Another way to vacuum a radiator is to remove the end caps and use the hose attachment on your vacuum cleaner to suck up any dirt or dust. Finally, you can also use a wet/dry vac to vacuum a radiator by removing the end caps and using the wet nozzle to suck up any liquid or dirt. Whichever method you choose, be sure to clean the radiator thoroughly so that it can function at its best.