I had the same problem for a couple years with leaking coolant when the weather got cold. It was not enough to puddle under the car, just enough to leak on the inner fender and lose a pint or two between oil changes. I could smell it leaking and even see the steam escaping at stop lights when it was below zero F (would have been a little unnerving if I didn't know what it was!) As soon as the weather warmed it would not leak as much, if at all. It only took 5 minutes to remove the tank and see the cracks to know where it was coming from, I was just too cheap to replace it with one that had a 50/50 chance of not making a year without cracking again. I finally did replace the tank and now no more leaking.
The first reply you got and all the others were giving you the right answer, just either replace the tank or live with it.