Okay, I just pulled my heater core from my 90 Deville because I have minimal heat. This is a brand new core I installed not quite 2 years ago because back then I had ZERO heat. Anyway, everything I've read on here HIGHLY recommends the BarsLeak Gold in the coolant system, so I've been putting it in. I just flushed the cooling system a few months ago, added DexCool and BarsLeak, as even after putting in a new radiator 1.5 years ago, the car still tends to overheat in the summer. Now, back to my point. I'm flushing out my heater core - and it's just FULL of chunky BarsLeak!!! No wonder I have minimal heat, the core is so clogged up with this stuff! Comments, suggestions?