Well, I took out the old thermostat tonight in my quest to purge the cooling system from Dexcool sludge. The t-stat was sludgy, the inside of the LIM coated, too. The sludge seems to wipe right off. Not tough to remove, if you can reach it.

After cleaning up the low coolant sensor, I tried to pop the o-ring seal off the edge of the thermostat. It crumbled and I had banked on reusing it. I'll get one tomorrow and refill with Prestone Super Radiator Flush/Water. Then I am going Peak Global Gold. Hopefully, that Prestone stuff will eat the sludge off the coolant passages.

This brings me to my question:

What do I need to do in order to upgrade the housing gasket from the paper one to the O-ring on the later models? Do I just need a later year housing? The surface of my LIM is flat. Do the o-ring cars have a groove in that area?

While I am in there maybe it is time for a lower temp T-stat...