90 cherokee laredo 4.0 water pump .. noises

i bought jeep in may with 108k miles (114.5 now)

noise started after I really used the heater for the 1st time for a few hours that day. & the 1st time I used 4 wheel drive in the snow, i was worried because the part time 4 wheel drive engaged pretty hard one time that night

sound is coming from area of crankshaft pulley / water pump... I finally found that the pulley on water pump is kinda loose & can see it kind of wobble when running. the sound does not get faster with engine rev .. oh yea, the heater does not get real warm inside the cab, was freezin a couple days ago

anyways, the noise is getting louder everytime i drive it. at first it would need to warm up a few minutes, then the sound started. sounds kinda like a loose bolt rattling in a metal box & fairly consistent pattern

so, is the pump shot or is the pulley just loose? ... or worn out pump shaft ? I dont know if its the original pump or not, bought it at auction w/ no history

OR .. is it the harmonic balancer / crankshaft pulley .. is there any way the 4 wheel drive kicking in really hard damage the crankshaft??

pumps are fairly cheap at least, so Im hoping thats all it is ... thanks (my 1st post)