Ok, my 94 3.4l firebird is overheating and burning coolants. It throws out massive amounts of white smoke and overheats in under a minute. I just replaced both headgaskets thinking that was the problem, but that didnt help anything. So cracked heads or block? how can i tell?

 

Were the heads resurfaced before replacing the gasket? Many times gasket failure is caused by warped heads. Also check the intake manifold gaskets.

 

Well if you think its a cracked head or something, its good to do a compression test.

Check for leaks in the radiator, near the hoses.

Also i agree, check the intake manifold gaskets. Thats where my money goes. the 3.4L are know for having leaks in the intake manifold gasket. Mostly because they are plastic. If you have high mileage, they usually fail around then

 

Thermostat... Although overheating in a minute is a bit crazy

 

well the car does have 150,000 miles and no i did not get the heads resurfaced. This is not just a coolant leak as in it is pouring massive amounts of white smoke out the tailpipes as if it is burning coolant. A whole tank of coolant is gone in about 4 minutes of driving. But doesnt leak when the car is not running. Obviously since i replaced the headgaskets i replaced the intake gaskets as well. So i doubt they are the problem. The guy i bought the car from took it to a mechanic who said it was a blwon headgasket, cracked head, or cracked block. So how do i tell exactly what it is

 

a compression test