the fans go of like crazy because they are 2 speed fans, controlled by relays, Check they are working on low speed, sohould come on around quarter temp, then hi speed will work if you turn the air con on.....
Very unlukely its the water pump, these are sound units, and only play up with external leaks...
If the fans arnt working on low speed, the temp will go right up, then the fans will kick in on hi speed to drop it down, it results in a very unstable temp guage
98 T5 gear box (was auto)
Wade 977b cam
AU bottem end
ELXR6 ported Head