If car isn't overheating, thermo doesn't ned to be changed. It's possible that then waterpump impellers are worn away, common problem. The heater cores are tricky to flush 100% with the way the hose system is designed, some have had good luck directly hooking to the core and flushing. Temp blend door also cause issues at times by not operating properly.
Lastly, with the electronic heat controls, resetting the control head has also yielded results.
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Wednesday, December 26th, 2007 AT 6:46 AM