So I pressure tested the system at 25 PSI (it's kinda high I know), I found three leaks.
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I don't know what this one is, I checked all above and around and there isn't a trail and it wouldn't drip for me.
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This one started at the front of the block where the water pump meets at the right side and ran down the seam to the oil pan and collected there.
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This one is leaking like a sieve under pressure.
The brand of radiator is Tong Yang (pretty sure they supply several Asian brands as well as Mopar) but their website doesn't list a part for the explorer so idk what this radiator was meant for.