Water gurgling sound in dash

Hi All,

I remember some past discussion about strange water gurgling sounds in or under the dash. I now have this in my 500E especially when going up hills or at start-up. What could it be? My car has about 110K miles. Sometimes it will fog the inside windows with moisture on start up as well, especially when its hot outside, but I don't know if these two symptoms are related or not. A data base search did not bring up anything other than air in the heater core.

Thanks for any advice,
Eric