Q: does this engine require the oil cooler to be changed after the engine is rebuilt on 2001 Jeep Grand Cherokee

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Will it hurt to reuse the oil cooler and not flush the radiator
(1) Answer
The oil cooler is either in good shape or bad. As long as it's in good shape, it could be reused, but it seems like if you are rebuilding the entire engine, it's better safe than sorry and you should replace it.

You should absolutely flush the radiator and change all of the coolant if you are rebuilding the engine. All of the fluids in the car should be changed.