Last winter, my heater started just blowing cool-cold air. I replaced the heater core at the beginning of January this year, heat worked for about a week and now it's started blowing cool-cold air again. Today, I have no idea if it is related in any way but I can hear liquid sloshing around when I accelerate. I don't smell anything sweet and the floors arent wet at all.... Please help! Id rather not take it to a shop if I don't have to.