Blown headgasket.

Take out plugs, and blip the starter. Water will squirt out at least one of the plug holes.

I would do two things.

1. Visual inspection of radiator

2. Test the radiator flow. It costs nothing and is easy to do.

See http://datsun1200.com/modules/mediawi ... adiator#Trouble_Diagnoses

It started to over heat while driving, I took the thermostat out and run it for half hour and it was great, then just now driving to work I notice its starting to run hot again, (no thermostat) get to work an it's just pissing out smoke and steam from the exhaust, It won't start at all now , the water was flowing great last night, so I don't think there will be a blockage? , can someone give me an explanation that's not worst case scenario . I'm honoring I haven't damaged the head or gasket , I wasent driving it hard either

Overheating while driving? Or only when you come to a stop (idling)?

so the ute has started to over heat while driving, im going to remove the thermostat when it cools down, if that dose not do anything its a blockage right? , its the standard fan, im looking into a thermo

Jus my 2 cents check engine timing,replace the radiator cap .

try this.

take off the bottom radiator hose, draining all the water.
stick the hose into the top of the radiator and turn it on
if the water does not flow into the radiator quickly i.e. if it overflows at all then maybe the core is blocked

a radiator should flow easily and quickly.... try it with the hose on one side then the other to see if this makes a difference

It's a simple test that only costs you a little time and water

I'll second an airflow problem. Perhaps a faulty electric fan setup.

sounds like you don't have a thermostat fitted. Or it could be faulty.

do you have the standard engine fan or an electric/thermo fan?

Sorry yes 1200 ute a12 , The block should be fairly clean, It was re built earlier this year , I checked the coolant a few days ago an it looked great, nice and green still , it's wierd , I let it idle for 20 minutes of a morning. And it's still cold , then middle of the day it over heats, could it possibly be the air temperature?? Is there any way to clear the core if it is blocked?