What should be the level of coolant in the expansion tank when the engine is cold from overnight?

I run my A/C all year around and I often have a small puddle of water under the car. This doesn't smell or "taste" like coolant. At this time of the year, this seems strange.

I just replace a bad upstream O2 sensor but this has nothing to do. What should be checked?

 

That's condensation from the cooling fins of the A/C Evaporator Core. Turn your A/C off and it will stop. You are wasting energy (and gas mileage) running your A/C and then heating your car to compensate for the A/C.

 

With respect, I can tell you that is not true. Running A/C all year around remove moisture particularly in winter and it keeps the refrigerant and oil lubricating the compressor for better and extended reliability. You can use the heater and A/C in same time at a setting temperature for improved air quality.

 

Regardless, the clear water dripping on the pavement after shut down IS condensation. There's even a condensation removal hose coming off the coils on your household cooler. It's the nature of the beast. Can't speak for the expansion tank as not being familiar with the later models. My finger tells me the coolant lever prior to building a fire under it.

 

Coolant level is indicated on the side of the expansion tank, low and high so have it in the middle when cold.
The condensate from the AC should drain onto the floor corresponding to the middle of the dash. If you look under the car when parked after a journey you will see if dripping.

 

You can tell me what is not true? --- that it uses more power and decreased gas mileage? Tons of studies that prove that. Also, it is basic thermodynamics and it should be obvious. A/C on, enables the clutch, Clutch engages compressor, compressor causes increases demand on engine, engine works harder, gas mileage is reduced. Running the A/C typically will cost you 1-2 mpg. That is "wasted mileage and energy" when you don't really need it.

Here are some articles that prove that I'm right.
https://www.plymouthrock.com/blog/do...y-gas-mileage/
https://www.consumerreports.org/fuel...or-ac-running/


Driving with the windows down on a hot day is equivalent to heating your car and running the A/C.

 

Correct.