Overheating Cavalier

My daughter’s 1998 Chevy Cavalier has been overheating. The coolant would seemingly disappear in a few days. I thought it may be a faulty cap, I saw coolant around the cap, but no dice. Today I noticed that as the car idled, the temp gauge started to climb, but the radiator was still cool. any ideas?

You’re describing a head gasket leak. The first thing you need to do is remove the oil level dip stick and check the level and condition of the oil. If the oil level is high and has a frothy/creamy texture, that’s where the coolant is going.

Tester

“The temperature gauge started to climb…” Past the normal level? Did the radiator fans come on? Is the overflow bottle full? If so, coolant could be going into the overflow bottle and out the drain tube. You might not see this loss.
The cooling system needs to be pressure tested. This will show where the leak is, internally, or, externally.
It’s possible that the thermostat isn’t opening. Then, the coolant wouldn’t go to the radiator, and the engine would get too hot.

The temp gauge is going past the normal level, the pressure seems to build and then the overflow bottle starts to steaming. I’m going to replace the thermostat tomorrow, I can do that much.
The oil level is fine, I changed the oil a week ago. If it’s the head gasket I guess I’ll take to the shop.

Steam in the overflow bottle doesn’t sound good! Did the radiator fans come on? They shoulda. Ok, the thermostat change is a minor expense. Might as well.

On Saturday, I replaced the thermostat and so far the car is not overheating. Thanks everyone.