Re: 99 taurus heater problem - mileage 93k
FYI, here is some information that I've gleaned from various sources over the years of Taurus ownership.
Th 3.0L vulcan engiine is an inherently durable engine (one of Ford's better ideas), however it was not built without some flaws. There were quite a number of them that didn't get properly cleaned out after the blocks were cast. This left casting media (silica, basically sand), in the water passages. This ends up turning into a sort of brown, abrasive "soup" that circulates through your cooling system (not one of Ford's better ideas!). Often it takes a couple of flushings to remove all of the grit from the system.
This "soup" will cause premature failure of the water pump impeller (basically your sand blasting the vanes everytime you run your engine).
The sediment in the cooling system also tends to accumulate in the heater core, plugging it, and eventually rendering it useless, or worse, causing it to leak.
Once plugged, the coolant follows the path of least resistance (the heater core bypass), and you get no heat.
My advice: Isolate and flush the heater core, then run some type of radiator flushing aid (there are several out there), for about a week. Now flush the entire system one more time. With 90,000 + miles on the car, if you haven't replaced the water pump yet, this would be a good time to do it. If you have recently, you should be all set. Either way, the total cost of the above steps should not be too prohibitive. It amounts to cheap insurance. I lost a 2000 Taurus because I was not educated to the cooling system issues. A leaky heater core, combined with lack of comunication (my daughter failed to inform me that the car was hissing when she parked it at school), roasted the engine at 96K.
BTW, I'm relatively new to the forum, but I've owned a '98, a '99, an '00 and an '02 Taurus. I'm pretty familiar with their trouble spots.
p.s. I haven't even touch on the blender door issue, but that doesn't sound like your problem.