In a message dated 11/29/00 5:57:23 PM, meed@MBARI.ORG writes:

<< How can one differentiate a leaking rear heater o-ring from a leaking
rear heater core? >>

Ed,

With the hoses attached, extricate the core from its housing.  Then, run the
engine until the coolant is good and hot.  When at operating temperature, the
source of a leak in any hydronic system will be obvious.  I hate to end on a
dour note but, unless someone careless previously worked on the heater, you
most likely have a leaking core.

Rich