On a bone stock, 96 BBB with 137k on the odo. Noticed the other morning that the heat wasn't blowing hot air. At best, it was warm when the fan was on low. When I cranked the fan up to the highest setting, the air got cooler. I popped the hood and noticed that the top heater hose going to the core was lukewarm and the bottom heater hose was hot to the touch. This is after a 30 minute drive to work in the morning. This is the second core in the car - I replaced the original several years ago. No leaks nor any strong coolant smell, so I'm wondering if its time to replace the core once again? Could it be anything else?