For about the last month, coolant temps have been fluctuating. Temp can go up to the third hash mark on the gauge, then back to the middle and back to the third hash mark. Temp has not been in the red. Fans are working. Coolant has also been disappearing. No cloud behind me, and exhaust doesn't smell like coolant. Coolant has also been coming out of the reservoir by the battery. Guess that's why it's disappearing. What could cause the coolant to do that? Car is a '96 Formula, with cai and catback.

 

Possibly air in the cooling system. Have you bled the system after adding coolant?

 

Faulty cap may not be holding pressure, allowing the coolant to boil and flow out the overflow. Or, a crack in the overflow line could be preventing the vacuum created when the radiator cools down from pulling coolant from the reservoir back into the radiator.

Borrow a pressure tester to find if there's a leak. The tester can also be used to test the cap pressure.

 

Go to autozone and borrow their radiator pressure tester.You give them 80 bucks and when you return it they give the money back.When I tested my radiator ,17lbs. I think,I had water squirting out of the radiator hoses because the clamps were not dead tight.One of the best things I have done to this car.Place a big towel under the hoses as to not spray on the distributor.Hope this helps.

 

I also got a real GM replacement correct # radiator cap and threw away that Stant one as my recovery tank didn't work with it.My02.

 

Thanks everyone. Looks like my weekend is planned.