Overheating car

SOURCE: No Heat and Overheating in 1999 Chevy Silverado

After replacing the thermostat, you must bleed the air from the cooling system.

To bleed air from the 2.2L and 2.5L engines, remove the plug or sensor on the top of the thermostat housing. Fill the radiator with coolant until the coolant comes out the hole. Since the plug is made out of steel and the thermostat housing is aluminum, it is a good idea to apply an anti-seizing compound or Teflon® tape on the plug threads prior to installation. Install the plug and continue to fill the radiator. This will vent all trapped air from the engine.

Any trapped air in the heating system will have to be displaced by coolant. Once the cooling system is filled, with the radiator cap off, turn of the heater at it's highest setting. Start the engine and allow it to reach operating temp. You should see a drop in the coolant level as the air in the heating system is displaced by coolant. Add coolant to the proper level and replace the radiator cap.

Keep a close eye on the coolant level for at least the next couple of weeks. The cooling system is a "closed" system. Any significant decrease in coolant level indicates a problem.

If you have any questions, let me know.

Please take the time to rate this solution.

Drive safe and be warm.

clarkco

SOURCE: running hot 1996 cavalier

please try a simple test for me. no.1: remove the radiator cap off the radiator. no.2: if you could see the see the radiator opening from within you car much better, then try to crank your car to an idle. if coolant blows out of the mouth of the radiator like an erupting volacano, then take note of this. no.3: while the engine is running at idle try to look at the coolant through the mouth of the radiator, if you see bubbles like washing your hands with soap and the suds trailing to a drain, then take note of this.

the reason why i'm telling you all of this is that, the coolant should flow like a clear stream. you don't have to worry about purging the system of air because, the water pump is already situated a few inches below the highest water capacity of the radiator. it means that if you drained your system and refiled the radiator to the brim, just start your engine and add a few more coolant to fill it up because the running engine simply purges the waterpump of air.

now, if you tried no.2, and you did see and somewhat like an errupting volcano, that means your engine is in serious trouble, so is no.3. however, a tolerable bubble flow is still possible but your valve clearances should be tuned if this happens. excessive bubbles accompanied by blow out of coolant means your combustion gases are seeping through the head gasket due to a damaged head gasket, warped cyclinder head, cracked cylinder head, or even a cracked cyclinder liner(or bore where the piston glides up and down). think back! did you ever experienced overheating you car to a point where it stalled completely? then, you need a thourough engine checkup.

SOURCE: My car (2003 Malibu) is

Check for blown head gaskets. GM aluminum-head engines are VERY UNFORGIVING when it comes to being overheated. The heads usually warp, resulting in blown head gaskets and repeated overheating like you are describing. One of the main symptoms will be that you fill the cooling system and open the bleader screws to get the air out of the system. Then you start the engine and run it until the cooling fan comes on. When the fan comes on, place your hand behind the cooling fan and see if the air coming through the radiator is HOT. If it is blowing cool air, the coolant is not flowing through the radiator like it should. This is usually caused by high pressure in the cooling system due to combustion gasses getting in.

SOURCE: why is coolant spitting out of reservor of 1999 chevy malibu

Probably a blown head gasket. Not an easy fix and not for the faint of heart.