Chevrolet Repair: over heating 1985 chev. truck 4-wh., radiator cap, surge tank

Question
I have replaced thermostat-radiator& cap- bottom hose.
now it boils the water out the surge tank & over heats.
  
   paul  

Answer
did you bleed the system to get all the air out? if you didnt, chances are you have a big air pocket right next to the thermostat. if thats the problem, there is no liqiud there to tell the thermostat to open, hence, the over heating. ok, it your thermostat is right at the end of the upper hose like most of them are, heres a trick. pull the upper hose off at the therm. housing. fill the rad till coolant comes out the hose. connect it and pull the same hose off the rad. now take coolant and fill the hose up, then connect it back to the rad, now, with the rad cap off, idle the engine till it gets to running temp. if the whole hose is warm, you should be good, that means the therm. is opening up and you shouldnt be overheating anymore. if half of the hose is hot and half cold, you still have an air pocket in there. try squeezing the hose a bunch of time to get coolant down there. that should take care of that. once the rad starts overflowing, youll know there is flow. put the cap back on and take for a test drive. should be ok. let me know how it turns out for you.