Me too, been catching whiffs of coolant and occasionally loosing a little fluid - but WTF, this time of year its hell on wheels for coolant system valves, gaskets and seals contracting and expanding with radical temp changes.

For sure, the best time of year for maintaining the system and making picayune repairs is June when the system is likely to give more honest indication of what it really needs. You will be flushing the entire system anyway at beginning of Summer per scheduled maintance, pulling and examining the thermostat and its gasket too - right? And then if you're really on your toes, you will be flushing it again in September after running maybe 15% coolant all Summer long. Meanwhile, if rubber thermostat gasket has become brittle or hardened, possibly leaking a bit in coldest temps, you will notice this when you maintain the system as you have been doing all along.