Very strong sickly sweet odor of hot coolant.  I examined the heater box
unit, and open/close valve with the engine warm and running.  No evidence
of a leak visible.  I read some posts about the open/close valve being
prone to leak, but not the sign of the slightest drip.

I did not rip open the heater box to examine the heater core.  Still no
sign of leaking underneath.  So where is it coming from?  It definitely is
emanating from the rear heater.  My nose knows. : )

This smell is driving me batty (more so than I already am, so they say).
Hope this odor is not DANGERous!  We have an 11 month baby girl who loves
to ride in the "Edelweiss."

Should I go ahead and order another heater core?

Thanks in advance
HK