I'll eventually tackle my problem of No-Heat in my 96 C.E. , I'll let this hot summer end first.  However, earlier this year I disconnected the in & out heater hoses of the heater core and back-flushed it until clear water came out.  Thinking I had fixed my problem, I hooked everything back up but still no heat.  I checked and made sure the door in the plenum was open to allow air to flow thru the core, and it was.  My question is:  If you can get water to flow thru the core from the in-hose to the out-hose of the core, does that "prove" the core isn't blocked?  Or, is the core engineered so that water can bypass a core blockage so that water can still flow between the in and out hoses?  I don't want to troubleshoot thinking the core is good when it may not be.  Hope I am making sense in how I am wording this.

It would be possible to have some of the core tubes partially blocked and still have some water flow in and out. However if you're getting good flow in and out core is likely o.k.

Thanks, I move forward in the belief the core is good.  But I'll tackle this later....108 degrees here today!  August bites.