Update:
Finally got to the thermostat... so the LS is back on the road after sitting for a couple months. If anyone remembers... mine was sticking on the way open... causing a rise-drop-rise situation on the way to full operating temps.
I took a couple pics. One of the old and new thermostat. At ambient temp it's easy to see why the old thermostat, (left), wasn't functioning properly. It was weak... after 81k miles.
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and... for those who think re-using the o-rings is acceptable... think again.
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Used o-ring on left... new o-ring on right. There is actually 1/8" difference in height between them. Sure... the old one will still seal.