Have been over at the farm the last week and have been using my WD45 with a freshly rebuilt engine. the weeds are so tall that the radiator gets half plugged and have to take it back to the house to blow it out. When I get to the house the temp gauge reads @ 180. After I shut it off and and blow it out the temp climbs. But after I fire it back up and idle it for a minute or 2 the temp gauge drops to the thermostat temp. So what you are experiencing is normal.