Good points brought up on this so far.  So lets summarize what could be
causing the low/no heat problem is:
1. Bad thermostat- If heat comes out of your rear heater then the thermostat
should be OK.
2. Air bubble in system- This is why Bentley says to open the heater valve
when bleeding the coolant system (do I hear a "dough" right about now?).
3. Possible coating of interior of heater core with Bar's Leak, etc.- This
stuff has been known to coat the inside of heater cores and radiators,
killing the heat transfer properties of both.

Hope this helps,
Ken Wilford
http://www.vanagain.com
John 3:16
Office (856)-765-1583
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