Since the expansion tank is easy to change and a common failure, initially just change that out. It's not imperative to overhaul the whole system when one component fails. It is fine to just replace the cracked tank. Certainly check hoses to see if any are soft but I would fill it up and bleed the system and see if it runs normally before doing anything further. Once it is up and running you can easily check to see if fan is operating normally and if there are any leaks. Be sure to check the water pump for a seeping leak out the front. Hopefully it was not running hot very long and the cracked expansion tank caused the overheating rather than something else. I agree that it is important to use and OE or OEM replacement.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas