If the heater blows hot air, then hot coolant is traveling through the
heater hoses from the engine to the heater coil and back and this is all
that means.  It has nothing to do with whether or not the hot coolant
travels to the radiator and back since there are completely different
sets of hoses for this function.

What it does probably mean is that the water pump isn't bad as it is
circulating the coolant through the heater lines.

Someone stated earlier that the heater hoses got hot coolant regardless
of whether the thermostat was open or closed, and that the thermostat
only controlled the flow of coolant to and from the radiator in those
much larger hoses.  If this is correct, and looking at pages 19.8, 19.9,
19.10, and 19.11 seem to confirm this, then the problem almost certainly
is the thermostat.  It is not opening to let the coolant circulate to
the radiator and back.  The limited volume of flow through the heater
hose loop is not sufficient to cool the engine properly.

As suggested before, take the thermostat out.  Replace it with one that
has tested good in the old pot of hot water on the stove top test.

Sam

--
Sam Walters
Baltimore, MD

89 Syncro GL, Zetec Inside
85 Westy Weekender
85 Mercedes Benz 300D Turbodiesel - to become veggie oil powered

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