I have a 2008 Kia Optima that I bought last year. The heat has stopped working. Comes out a little warm at best, even after driving for a long time. Thermostat has been replaced, plenty of antifreeze in it, heater core checked for clogs (someone put something in the lines that the mechanic couldn't identify but it's been flushed out, they assumed it clogged the heater core but someone else tested it and it flowed fine). Antifreeze does not get hot. I can drive for 20 minutes and you can take the cap off the radiator and put your finger in it. It'll be lukewarm. The heater hoses were taken off when we checked the core for clogs and I was told to start the engine. Water trickled out of the lines straight out of the heater core but I was told it should be gushing. The car does not overheat, whether driving or idling. There are no leaks. I'm wondering if it might be the water pump. I wanted to check if it could be something else before sinking money into replacing the pump. Thank you for any input you might have! As a woman, I often get suspicious taking it to a shop because they could tell me anything and I wouldn't know if it was true or not.