How do i know if i have a blown head gasket

 

A compression test will show it if the leak is between two cylinders. A coolant gas test will see it if it is between combustion chamber and coolant passages (although that could also be a cracked head).

Why do you ask?

 

When i stop at a red light then pull off white smoke Come from the left tail pipe. Could the be a blown headgasket or do i need a oil change

 

White smoke is coolant.

Oil is more of a blue-ish color, if you needed an oil change or car would get a lot hotter.

 

Could be a cracked head as well.

Did the car overheat?

 

I Had it for a month now and it haven't over heated since i had it. The only thing i done to it was a oil change, new water pump, and change the radiator coolant. The guy i bought it from said the motor was knocking but it haven't knocked since i had it. I notice today that the temp gauge wasn't working.

 

I'd pull the plugs and see which one(s) are are wet and than start the compression test on that side first. They sell kits that aren't too expensive and well worth it if you ask me. From there, if you find a dip in the reading that is below acceptable range, do a leak down test on that cylinder. That will tell you what your problem is. if you see bubbles in the radiator that means you got a bad head gasket. if you hear air coming out of the plenum you have stuck valves.

Also, does the car run rough? With coolant getting in the system it should cause a misfire.

Also, are you sure you seen burnt coolant and not exhaust fumes from it being cold?