Im sure everyone is familiar with the dex cool slugde issue, and I'd like to hear opinions on why this happens. Anywho, with the winter months coming i decided i should go ahead and tackle the problem and hope I didn't have to replace a radiator or heater core. Got Blue Devil coolant flush. Flushed once with water alone (distilled). then 15 mins with the blue devil with the heat blasting. two more water flushes then Prestone GM Approved. And oh yeah, a tstat. It threw a po128 a few times when the weather was cooler and i suspected it was stuck open. one of the more PITA thermostat housings i have encountered for sure!