Hyundai Repair: Hyundai Elantra GLS, Radaitor repair, coolant temperature sensor, hyundai elantra gls

Question
There was a crack in my radiator so I replaced it, now it is over heating (boiling) Seems to be worse than before.  I have let the car run for approx. 45 and it was ok and then I tried to drive to gas station and it over heated.  Any suggestions?  Thank you,

Calvin

Answer
It's possible the thermostat was damaged or the cylinder head warped by the overheating.  You'll want to check the overall system operation:

1.  Start the engine and turn on the A/C.  Both radiator fans should run.  Turn back off after observing.

If both fans do not run, you've an electrical issue with the fan circuit.

2.  Add coolant to near the top of the radiator.
3.  Leave radiator cap off and start engine with the a/c off.

Over time, the coolant should begin to flow.  Typically, this is observable through the cap opening in the top of the radiator.  If the filler neck sufficiently impedes your ability to see the flow, you can also check for flow by feeling the radiator hoses.  Of only one is hot, coolant is not flowing.  You should see evidence of coolant flow prior to the fans starting.  If you do not see such evidence, you should expect that the thermostat is stuck shut.

4.  In a short period of time after coolant flow, the fans should begin to run.  

If the fans do not run prior to boiling, you've either a problem with the coolant temperature sensor which controls fan operation or you've a cylinder head issue.

If you find the vehicle is difficult to start (excessive cranking and runs abnormally poor) when cold, you should immediately expect that the cylinder head is warped beyond repair and will need replacement.