[richardbessey]

Re: 9860 sts overheat

Just a couple ideas:
Blown head gasket?

• 
  Does the water pump generate any pressure?
  Have you checked the temperature of the radiator? Does it match the engine temp (It should if the water pump is working)
  Try hitting only the radiator with a garden hose, if the engine temp drops, it is an airflow problem.
  Engine timing correct? Has the timing been advanced on the engine?
  
  

 

[richardbessey]

Re: 9860 sts overheat

Is the radiator hose supplying the water pump collapsing due to suction from the pump?

 

[richardbessey]

Re: 9860 sts overheat

Faulty radiator cap.
Loose fan belt/oil on fan belt