Hello Scotty. Recently purchased a lexus is350 now im starting to see my temperature gauge go up when idling and once I start driving the gauge starts to go back to normal. I filled up the radiator with coolant yesterday and drove around now in the morning I checked it and its empty I see no coolant on the floor, I checked the thermostat but and it seems new but I speculate its not OEM. I cant turn on the ac because it will overheat instantly and when I turn the heater on cool air comes out. Yesterday I took it to a local mechanic and waited for the car to cool down for like 15-20 minutes he added coolant once he turned the car on without the cap on the radiator shot the coolant all over the place.
Replace your temperature sending unit. If coolant came out the top of the radiator, your thermostat is working properly. Make sure after adding coolant that all the air is properly burped out of the system. If not, you'll get hot spots and false temperature readings.
