I've been losing coolant for as long as I've been checking my coolant (since last summer). I want to fix the problem. About two weeks ago, there was nothing I could see in the radiator cap and nothing in the overfill bottle. I've never noticed anything weird about the water temperature, and the heater stays comfortably warm when the temperature is 20 degrees Fahrenheit outside (once warmed up).

Today I filled the radiator cap to the top, and the overfill bottle to the max line and let the car heat up. I'm not leaking coolant that I know of, I've never seen any on the ground.

Where is all this coolant going?

 

my car lost coolant to, turned out to be a hole on one of the hoses

 

do a pressure check. you might be leaking on one of the hoses behind the engine.

 

I'm guessing you have several miles on the car. ON my 97 civic EX, my side tanks on my radiator started leaking, and was replaced. Also, on a 94 Accord, it was losing coolant but I couldn't find where. So someone recommended using powder aluminum in the coolant which is intended to stop leaks. Ended up SHOWING me where the leak was as it make the leak worse: the top tank of the radiator. It was too far gone for a simple fix like that so a new radiator was installed and fixed the prob.

 

Check your water pump/gasket also...

Also check to see if its not leaking into your oil..