coolant issues

Have been smelling coolant after parking my car in the garage, though not every single time. No sign of leaks or puddles. Check coolant reservoir and it looked low. Since my annual service was due, I mentioned it and was told that the coolant is almost full and that the level depends on the...

Ive replaced my Fan control module, Thermostat, and coolant temp sensor, The Temp gauge still isnt working, the heat blows cold air, and when i feel the hose under the hood its cool feeling. And im smelling a slight coolant smell... all advice is appreciated ....