I got home from a 15 minute drive across town with a 30 minute cool down period and then a 10 minute drive back across town. I got out and after a couple of minutes I noticed a noise coming from the 80. Popped the hood and the coolant was boiling. The overflow was almost full but it is still too hot to take the cap off the rad. I searched and didn't find much really. I changed out the typical sludgy mixture last fall for 50/50 red and tap water and the level has not dropped since, so I don't think I have a head gasket issue. What could be causing this? Ambient temp was ~85-90 and I had the AC on. I have an ARB with IPF 800's on it that could be restricting air flow I suppose. This is my first really hot day I have driven the 80, but I know this shouldn't be happening.