> 
> Yes and No.
> 
> The heater core's are within the coolant loop when the valves are open.
> 
> If the thermostst was stuck closed, turning on the fan motor's wouldn't
> drop the operating temps any.
> 
> It would stay hot.
> 
> Seeing as the temp's fluctuate on the gauge depending if the AC is on or
> not, I'd bet the raditaor is half plugged.

OK. I think I might understand what you were attempting to communicate. You 
don't say whether you're talking about the RADIATOR fan or the HEATER fan. 
Since the subject was the heater, I assumed heater fan. You are indeed 
correct that a stuck thermostat doesn't generally allow ANY water through to 
the radiator. Subsequently, since the RADIATOR fan running is generally a 
sign that there's water getting to the radiator, it is indeed more likely a 
radiator blockage issue. Still, I've seen thermostats refuse to open 
reliably, and even STICK partly open before, and that's not too difficult to 
check.

One question.
> Who would drop a new engine in a vehicle without updating the cooling
> system ?
> I sure wouldn't, and chance frying it.

Indeed. I wouldn't (and don't!) either. Even if, by some strange occurance, 
it IS the thermostat, I'd STILL replace the old radiator. C'mon, it's $150 
and an afternoon's work, right? Cheap insurance. The PO of my van ruined the 
head gaskets on my van by plugging up the radiator with Barr's, causing 
repeated overheats. Bad radiator=bad news.

-- 
John Bange
'90 Vanagon
"Keine Bange, wir holen die Zange!"