wiered problem - coolant/temp/heater

hi all,

1997, Lumina LS 3.1/212,500miles

today morning, it will a bit cold, so i have turned the heater on for about 10 minutes then turn it off.

in the afternoon, i drove my car with a/c on, and noticed a very high coolant temperature...and raising. the needle was in a very visible motion of increasing and sometime decreasing with the same speed.
even on idle the temperature is very high...even the fan are not doing any good to the temperature either.

now, when i came back home, i have open the hood and found out that there was no coolant in the coolant reserhevoir....again i have filled it up with some water and turned the car on....still temp was high...then (just to check) i have opened the two bleed screws and found that only air is coming out of them with a lot of pressure - from both of them.

now, i got no idea what happened to my car...i have only turned the heater on in the morning...and thats it.

i have never faced any overheating problem before and all just worked fine till today morning.

Please help me to find the problem.

Thanks and Best Regards

Did you ever get your LIM done? Check for any visible leaks in the drive/car park after letting it run, or get it pressure tested.

Not sure what to tell you. You lost coolant somewhere along the lines, just gotta find out where.

just by turning the heater on?....what does this cause?

can you help in explaining the process? (that might help to find the problem)

Thanks and Best Regards

Intake Gaskets are known issues on these cars and commonly they leak on the back side of the engine and are difficult to spot - you'll need a mirror and a flashlight while the engine is running and full of coolant to find if that's the cause.

your varied temps could be attributed to an air pocket: as you state there was tons of air when you opened the bleed valves.