97 Sable - no heat

My son's 97 Sable with 3.0 pushrod engine, overheated on startup after a long drive then being parked for half an hour or so. After an overnight cooldown, the gauge would read hot and the cap would begin to spew within a
few minutes of running. I took out the thermostat and confirmed it was bad by boiling it on the kitchen stove. (At a rolling boil, it would open maybe a sixteenth of an inch at most.)
I flushed out the old coolant, which was brown, and ran it for a week with no thermostat and a bottle of Prestone super radiator cleaner in it, then flushed all that out. I isolated the heater circuit from the engine and ran lots of water through the core in both directions.
With everything back together and a new thermostat installed, it runs fine, the temperature gauge reads normal, but there's no heat. (The heater worked normally before the thermostat problem.) The heater hoses are hot to within an inch or so of the core fittings, the bypass hose is hot, but the core metal is cold. What could be going on here? It sounds like a core blockage, but each time I've flushed the core, it's appeared to have plenty of flow.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ernest Scribbler wrote:

insulator. It won't flush out. The brown coolant leads me to believe this is the case. These cars also have a history of water pump impeller erosion due to corrosion in the cooling system. This could be exacerbating the problem due to low coolant flow. You've flushed the system, so I would suggest that your next step be the water pump. They are inexpensive and not hard to change, and it's likely near due anyway. If this doesn't take care of the problem, then consider replacing the core. This calls for removing the instrument panel.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Tom Adkins" wrote

That's my plan of attack for today.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

And here's the problem: http://blizzard.zmm.com/waterpump/
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
That's great, ES! Well done... you know it'd be a great service if you joined taurusclub and posted that! And kept that pic on the server. Check this: http://www.taurusclub.com/forum/index.php?showtopicc66

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
And aint the Vulcan just a freaking GREAT ENGINE!!!!!!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.