What's wrong with my G20?

[Mark Joplin]

"Johnston, James W" wrote:
> -Last night, I saw steam coming from coolant boiling off the exhaust
> manifold blowing from under the hood...quite a bit.  I killed the engine
> right there.  TEMP GAUGE DID NOT REGISTER THE OVERHEAT.

Could it be that the cooling system has air in it?  The cooling system
is susceptible to overheat if you don't 'burp' all the air out when
changing coolant.  I suspect that the temp gauge will be all over the
place if the fluid is not topped up and in contact with the sensor.
Here's a filling procedure with ways to bleed the air if you don't
have a FSM:
http://www.zotz.com/nissan/proc/sentra_se-r/sentra_se-r_coolant_change.htm

"Coolant boiling off the exhaust manifold" ..... find a leak?