Are you supposed to bleed the radiator after installing a new radiator?

In most systems you need a way to remove any trapped air. With your van it's not a hard process, fill the radiator to the top, then fill the reservoir to the max line. Go out and drive around until the engine is at full temperature, go home and park it. Once it cools down, check the levels again and add as needed. Repeat until it stabilizes.

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars