[Healeys] thermostat discussion

[BJ8 Healeys]

"The temperature is regulated by the thermostat, more or less."
[TRUE, as long as coolant temperature is below the rated temperature of the
thermostat]

"If more heat is developed it will open further to allow 
more cooling..."
[TRUE, as long as the thermostat is not already open to the max.]

"...to drop the temperature to the set level."
[NOT EXACTLY.  The function of the automotive thermostat is not to maintain
the coolant temperature at a "set" point (as in a house), but only to
restrict the flow of coolant to the radiator until the engine warms up to
operating temperature.  The automotive thermostat is a completely passive
device, responding to coolant temperature but not controlling it (except as
it restricts coolant flow during warmup).  At its rated temperature, the
thermostat begins to open in response to increasing coolant temperature, and
will continue to do so until it is wide open.  At that point, it has no
further ability to do anything to restrict coolant flow.  
It's a common misconception that installing a "lower temperature" thermostat
will help to cool the engine.  

Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC  USA
----------------------

Hmm,
Not so sure about this. The temperature is regulated by the thermostat, more
or less. If more heat is developped it will open further to allow more
cooling to drop the temperature to the set level.
The reading also depends on where the sensor is placed. In the cilinder
head, intake manifold, thermostat housing, top of radiator etc.
Changing over the thermostats may cast some light here? Just to see what
happens.
Kees Oudesluijs
NL