Please Help, Overheating problem

[180s-ex]

Hello
I just bought my 240sx with a hole in the rad. so i changed the rad, now it is overheating! i took the cap off as its running and it seems to be pulsing up and down, not moving around like running water like i thought i should be. when i apply throttle, it starts to overflow continuously as if there is something stopping it from circulating.
does this sound like a thermostat stuck shut? or possibly a leaking headgasket?
please help me out i am broke and its my daily ride!

thanks

[HalveBlue]

Try bleeding the system of air.

Easiest things first.

FSM shows you the steps, but the process is pretty simple.

1. Put heater on full and open the vents.

2. Loosen coolant bleeder hole.

3. Run engine.

4. Wait for coolant to start pouring from bleeder hole then tighten down the bleeder screw again.

Done!

It helps to have the front of the car elevated slightly to force the air out of the coolant system more easily.

Also, you may have to repeat the process a couple of times. If warm air is blowing out of the vents you've done it right.