A few nights ago as i was driving home at night, i noticed my temp gauge needle dropped all the way down. My CEL, VSC, and VSC OFF light lit up. Shortly after, the temp gauge needle raised all the way up for a few seconds, then dropped all the way back down. It stayed down for the rest of the way home (about 5 miles). As soon as i got home, I turned off my car in the driveway (driveway is inclined) and saw what I thought was smoke coming from under my hood. I popped my hood open and saw what thought was smoke but actually was steam coming from a hole on the small overflow rubber hose connected to the reservoir tank.

My car is a 2003 GS300 with about 140k miles. I haven't done any coolant preventive maintenance on the car yet (thermostat, WP, radiator, hoses, etc.) and im not too sure if the previous owner did also. I bought the car used from a dealership about 4 years ago.

I rented a coolant pressure tester from oreillys and will test the system for leaks tomorrow after work. I did notice the radiator was low or empty of coolant, and noticed dried coolant around the radiator cap. I took a quick look around the water pump and thermostat and didnt see any leaks. I did notice my splash guard is still wet and im not too sure if theres a leak coming from the bottom of my radiator or it was from the overflow tube.

My question is, why would my temp gauge needle drop, spike all the way up, and dropped and have CEL to turn on?


CEL, VSC, and VSC OFF light on and temp needle down





Temp needle all the way up for a few seconds before dropping back down

 

You need to pull the code.

 

While replacing the coolant that I lost, I realized my radiator cap was missing the rubber piece in the middle. Luckily I bought a new cap and replaced it after topping off my fluids. I also disconnected my battery to clear the CEL. I idled the car for at least 30 min and took it for a test drive. Car doesn't overheat. Problem was fixed! Silly radiator cap!