I'm still highly suspect of plastic ThermoStat Housing;
may just leak when engine is at higher RPMs & higher coolant system pressures\temps.
If there's even a small "wet spot" anywhere around the TStatHousing, take that plastic junk out, shoot it with a 12gauge,
then install an Aluminum ThermoStat Housing & get rid of this worry forever.
In early 2019 & 19+ years, the FactoryOE ThermoStat Housing on my 2001 Ford ExplorerSportTrac started to leak per the pics below; at first just an irritation, this leak steadily grew much worse. Under the Throttle on the V6~4.0L~SOHC engines TopFront in several 1997~2012 models, the FactoryOE...
2001fordexplorersporttrac.fandom.com