I haven't updated this in a while. Haven't done a whole lot to it.
The CEL came on a while back and it was the rear O2 sensor. I went ahead and replaced both with new Denso sensors.
A few weeks ago it started losing coolant slowly and I could smell antifreeze. I couldn't find any leak, so I thought (hoped) maybe the radiator cap was bad. I put a new one on it. It then promptly blew one of the metal lines going to the rear heat. It must have had a pin hole and just barely leaking when pressurized. It was right above the catalytic converter heat shield. It never left a puddle, so all I can figure is it only leaked under pressure and evaporated off the shield. I bypassed the rear heat. Then it blew two more hoses and the water pump seal all within a week.
I was afraid it was the head gasket, so I got my friend who is a real mechanic to check it out. Compression and pressure tests all good. Apparently the new radiator cap was defective and holding way too much pressure.
I went ahead and flushed the system and replaced all coolant and heater hoses with new, new water pump, new thermostat, and of course I returned the radiator cap and exchanged it. Problem solved, but rear heat is still bypassed.
We took it on a road trip to the gulf coast and just got back this afternoon. 1600+ miles without a single issue and got 15 mpg.