2005 Chevrolet Cobalt Overheating and Coolant leak?

RONNIE21

MEMBER
2005 CHEVROLET COBALT
2.2L
4 CYL
FWD
AUTOMATIC
175,902 MILES

I am Having problems with my Cobalt. I was recently in traffic with my AC on. My coolant temperature reached 230 degrees when my car started To overheat. There was White smoke coming from the drivers side underneath the hood where my coolant reservoir is located. So I turned off my AC and pulled over, as I got out the car, I noticed coolant leaking from under my car on the drivers side. Coolant only leaks out when My car Overheats, this has Happened before, but I don't know what is causing my car to overheat. The same day, my Radiator was replaced. So it shouldn't be the Radiator. My coolant temperature Goes up and down when I'm in stop and go Traffic. If I'm in constant moving traffic like a Highway, my coolant Temperature is usually at 180-200 degrees. But if I'm sitting and My car idles, it has been overheating lately. Can you Please help!

1 Reply

ED-WEEZY21

MECHANIC
248 POSTS

Ok so first off, coolant leaking out of the reservoir will almost always happen when a vehicle overheats. Overheating will lead to major problems. I'm going to safely assume that the overheating cracked the radiator which is usually the first thing to go. Idling in traffic is the worst for a vehicle especially on the highway. The road is extremely hot and the vehicle sitting on it without moving pushes the temperature past its limits hence why you're not overheating while driving because your forcing air through the engine. I would check to make sure that your cooling fans are turning on. If they're not, I would check all of your relays and fuses. If the fans do kick on, check to make sure your thermostat isn't staying closed. A proper working thermostat will open when the vehicle reaches normal operating temperature which is around 180-200. Easiest way to check is to first turn on the vehicle when its cold and let it idle for a little bit. The upper radiator hose should start warming up and getting hot while the lower radiator hose will still be cold. When the vehicle reaches normal operating temperature, the thermostat should open up and releases all of the heated up coolant through the lower radiator hose and the lower radiator hose should start to become hot. If it does not, you have a stuck closed thermostat. Lets start with the above and let me know what you find.