Recently purchased a 98 sr5 with 260000 on it and didn't pay much attention to the heating capabilities. It's not bad but certainly isn't as warm as it should be. What's a good starting point to get more heat flowing? Thermostat and/or maybe a core flush? Also, the hot-cold air knob is fairly difficult to turn while making some hard clicking noises and I'm not sure if the knob is fully turning to the hot or cold side. Are these clicking noises normal or should it turn smooth?