Cooling Leak/Heater Irregularities

I have a 1993 190E 2.6 and have 2 perplexing problems.

First is a slow coolant leak. Intermittently I notice coolant on the ground though this leak is quite slow, as I only have to add coolant once a month or so. Sometimes when the level is low I will hear a gurgling sound though this is not all of the time. The funny thing is after many inspections under various conditions I am unable to notice any leaks or fluid anywhere. All I ever see is a little spot of coolant under the car.

Second, my heater seems to have a mind of its own. I leave the temperature adjustment wheel in the same position (70 deg) and the temperature of the air blowing through the different vents will vary from hot to clod and back to hot again.

Is it possible that these two problems are related?

I greatly appreciate any help and guidance anyone can offer.