r/Cartalk • u/Zufalstvo • 1d ago
Engine Cooling Temperature gauge issue
So I'm having an issue with my 2015 Malibu. I've got a check engine light so I'm going to get the codes later today but I wanted your guys' opinions in the meantime. Also, I drove it into work today, about a 35 minute drive, and had no issues, so I don't know if I should be imminently concerned or not.
Yesterday, the temperature gauge stopped detecting engine temp, and when I got home the radiator fan was blowing for a while after I shut my car off, which it pretty much never does, even on a hot day.
It did the same thing this morning after driving it to work, and the check engine light came on today. I turned off the car and let it sit for about an hour last night, then turned it on and off again, and the fan blew again.
So I don't think it's overheating, I suspect it's a sensor of some kind. I'm just wondering how concerned I should be, and I plan on getting the codes and trying to fix it after work today
As a side note, I smashed my radiator a year ago, hit a deer at low speed and kind of caved it in, the fan housing is split as well, but it works perfectly fine, fans spin and everything. Haven't seen a coolant leak anywhere. But I really don't think it's overheating so I'm not too worried
2
u/chayashida 23h ago edited 23h ago
STOP DRIVING THE CAR.
If you are having problems with the cooling system and you keep driving the car, this problem can go from "Oh it's a minor problem" to "I need a new engine."
The temperature gauge won't always tell you what the coolant temperature is. When the thermostat fails, the valve is supposed to fail to an open state, letting all the coolant circulate through the engine.
But when there is a problem, the temperature gauge might still read "cold" while the engine itself is getting hotter and hotter because the coolant isn't pumping out of the engine, being cooled in the radiator, and the flowing back through the engine again.
When you have a coolant leak, you won't necessarily see a puddle of coolant on the ground - it can just evaporate into the atmosphere. So the only way to know is to look at the coolant levels (don't do this right after you drive the car. let it sit.) If there's a full radiator and there's coolant in the overflow bottle, then it can be something else (like a failed water pump).
Especially with the damaged radiator, it's sounding like you might not have coolant properly flowing through the system, and if you run the engine you can get to the point where you do major damage.
Get this looked at
Quick story time: Buddy broght a brand-new car to the racetrack. Wasn't really a car guy, but decided to look under the hood and "do stuff" since the rest of us were checking on our cars. (It was brand new - there wasn't really much to check or fix.) He took off the radiator cap to look at the coolant, and didn't put it back on properly. Raced for a session (about 15 min). But said it felt like the car didn't have power when he pulled in.
We all looked under the hood, and noticed that the radiator cap was off. He said that the temp gauge never said that it was overheating. But all the coolant had boiled off. We weren't getting compression on the cylinders anymore. Engine was cooked.