4g64 rattling noise under low rpm

so i've been experiencing this issue where there's this loud rattling noise (best i could think of are metal shot being jiggled in a metal can) that happens when the outlander's moving and the revs are between 1k-2k rpm.

the dealership said it was the water pump. a shop i went to says the water pump was still good (though close to replacing), and while the belt and tensioner were replaced (one part of the tensioner's mount was broken, making it wiggle a lot under load and the belt's sides were frayed), the noise was still present (though it doesn't happen as much as before). any idea on what it is? TIA :)

anyway...

after replacing the water pump, noise went away. problem solved. :)