Chevy 2000 Silverado 1500, the engine stalls and won't start until it has cooled off.

SOURCE: COBALT TEMP GAUGE READS 250 DEGREES BUT ENGINE

Probably the temp gauge itself. Most of the time it doesn't have a problem but sometimes they do go bad. Did the car ever overheat prior to changing the solenoid?

SOURCE: the temp was always at 180 the last week its gone

It could just be a bad thermostat. Its the cheapest part and easy to replace on that engine. I amagine you have some miles on it, mine went out at around 85000 miles, and it only took me about 1/2 an hour to replace. Also just to make sure, check the fluid level in the radiator not the over flow tank. I hope this helps you.

SOURCE: i have a 97 blazer starts fine stalls at 230deg starts when cool

Check the electronics in the distributor. Chevs are notorious for the electronics going bad inside of the distributor.

SOURCE: I HAVE A 2007 CHEVY COBALT THE CHECK ENGINE LIGHT

I had this problem with a 2007 Chevy Cobalt. I changed the coolant sensor and even though the check engine light went out I still had a reading of "---" on the coolant gauge. The problem is most likely one of three things: a low coolant level, a bad coolant sensor, or the thermostat needs to be replaced. The only other possible thing it could be is a bad BCM (Body Control Module) which in that case you would most likely be having other weird problems.

The Thermostat and the sensor are both very easy to get to and replace. Take off the engine cover by removing the oil cap and they are both to the rear of the engine on the driver's side. They are right next to each other.

Hope this helps!

SOURCE: My 2007 Chevy HHR 2.2L, coolant temp sensor is

Sure the engine coolant will be warmer than the outside temperture and if the car has been sitting a long time in cold weather and the outside temperture warms up it could be the other way around. The coolant temperture sensers aren't real accurate as they are a relaitive senser beween hot and cold and the numbers reported don't have to be real just the change from hot to cold and the reching of the coolant to the operating temperture. Noe it the senser doesn't read the opertating temperture coprrectly you'll have all kinds of problems. The therostaste will try to set the temperture of the water to it's set temperture and can open or close completly to get 195 degrees F. Many times if it's too cold then the stat is bad and needs to be replaced This shows up in alot of cars first thing after winter and the first onset of cold weather when the daily tempertures vary the most from day to night.