I have seen water pumps that get all gunked up. Is there any chance you mixed DEX cool and another type of coolant at any time. I think if it was me, I would pick up some radiator flush and do a real good flush of the system. When over heating, it is for the most part, poor coolant flow. This can be caused by a obstruction, blocked radiator, collapsed hose, stuck closed thermostat (although I will admit, I've never seen this), or gummed up water pump. Flush the system and that should deal with most of the causes.
SAVING THE WORLD ONE BONNEVILLE AT A TIME
1997,1998,2000,2005 year confused Bonneville SSExi. Stock? ish.
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