Out of curiosity, when did you notice the engine temp was not
what it should be? Was it coincidental with work performed?
A running fan as mentioned or an improper or defective thermostat
could make the motor run cool. Never heard of a water pump causing
an engine to run cool, stuck open or missing thermostat, yes.
Most scan tools will give you an engine coolant temp reading that will give
you something firm to go by, what is the temp range for operations?
Post some temps for the audience to chew on please.