300tdi knocking noise need help

Hi people. So my disco 1 300tdi started making a knocking noise from either the alternator water pump sort of area. I replaced the water pump and put a new belt on the noise is still there. So I removed the belt and started the engine and it sounds normal no knocking no squeaking sounds just like it should. I have tightened all the bolts to the correct Newton meter as said it the manual. If anyone has had this problem could you please enlighten me as it's becoming a stressful few days

Serpentine belt runs round a lot of parts there.

Did you notice any play or backlash from alternator or belt tensioner pulley?

The bearings tend to expire on the tensioner but they are cheap enough to replace so i would probably start there and also check the crank pulley hasn't come loose or the sheath delaminated from the harmonic balancer