Did you notice any good reduction in CPU temp after installing the water pump?
I used to have AIO water pump with 240mm radiator for my i5 6600k, and in some pressure tests the CPU temp were hitting 90C for less than a sec and return back to less than 60C. Not sure if it is normal to happen I think it depends on the pressure tests used, because while gaming and doing other staffs it was not exceeding 65C.
However, just to make sure that things are going well, I suggest that you check and make sure that you have installed the pump over the CPU properly with all 4 corners are balanced and the thermal paste is spread over the CPU. Some say that you don't need to tighten the screws of the pump too much and cause a pressure over the CPU...