How To Detect Coolant Lose -WHAT TO DO -help!!1994 Grand Prix

[Rockys]

We have a 1994 Grand Prix SE with a 3.1, we flushed the radiator last fall, now it seems to loose about 1 quart a week. There are no visible leaks, inside floor dry also. There seems to be only minimal fog out exhaust. Did miss the other day, but hasn't since. Did run hot for a few miles, then that went away. Not sure what to do. There is 150,000 miles on the car. Could use any help, what do we need to check. Sure hope someone can help. Thanks

[cayton69]

i had the same sort of problem with my old 91 cavalier with the 3.1 in it. the coolant tank had to have a certain level of coolant in it or else it would push the coolant out of the run off hose. it was a closed system so the tank was a pressurized part of the system. if this is the same setup as your grand prix, it might not be losing any, but venting excess due to overfilling

[kilroypr]

If you flushed your car, did you replace the radiator cap as well? Sometimes when systems are flushed they tend to disipate heat better, thus, heating water more. If the cap has the spring worn out then the pressure would make it open a little and the water would dissipate as vapor.

[hardywang]

Is it possible lower intake gasket or header gasket?