I am not motor guy, im learning as I go but, I had a similar problem with my 92 200 carb when I first got it. My buzzer would work, to well seemed like...lol. What it was, was when I went through an idle zone I didnt idle long and it would go off, temp would go up to 160-165 with psi of 3-4. I changed the water pump and put a new water pump housing as mine wasnt the prettiest, and now I have around 8 at idle and the buzzer hasnt went off. I thought it was broke an crossed it over and it worked so, my cooling issue was solved with a new water pump. That is my experiance with this problem, somewhat simple.