low coolant in midst of nasty chicago winter

[gymkata]

I got this "Low coolant" to come on after the car shut down. I took a look at the coolant level and topped it off. I have had to top off the coolant 1 time before last year and it turned out that the water pump was going bad. I hope that it's not going bad again!
Anyways, I don't see any leaks nor do I see any spots on the snow or garage. I had to add about 1/8 of a gallon to the radiator to fill up the expansion tank.
Any thoughts?

[filmy540i/6]

Those coolant level sensors are a bitch. They go bad intermittently for no reason whatsoever. Keep your eye on the coolant level, but I'd bet that things calm down now that you've opened up the reservoir and "loosened" everything up by topping it off.

[M20B25power]

Hopefully the w/p is not leaking coolant onto the fan area or a hot spot and evaporating, which may explain the lack of visible leaks when parked.

[repenttokyo]

I get mine if there' a temp flux outside, or if i park on an incline sometimes.

[tim eh?]

when it gets really cold my car piddles itself a bit around the heater core somewhere... i might ride it out until spring, but my coolant level sensor is disconnected so i have to check it almost daily :(

[BMWCCA1]

Using one pint of coolant in over a year isn't a big deal. That's why there's a place to check the level in the first place. Of course the best thing to do would be to pressure test your cooling system, including the cap. Water pumps often leak when they're not running or not under pressure, like sitting over night. But you say you have no spots or puddles. Visit your local chain auto-parts emporium and borrow a pressure tester. Get the system up to operating pressure and see how long it holds. Then test the cap. Watch out for exploding plastic radiators, too.