There's good reasons to use plastic impellers…. that's not the subject here though.
Generally speaking, the BMW cooling systems are known for failure. Replace it all, or run the risk of warping your head.
'99 528i ('98/12 build). 174,000km BY29428/Royalrot
Breaking My Wallet since 2009
Mods: Stoptech SS brake hose, 280piece toolkit resting on trunk floor, Beisan VANOS seals
'99 540i (grandfather's)