--- Michael Graziano <mgrazian@ltcm.com> wrote:
> Hey all. Just a quick question, and a quick story.....
>
> 1. WHat's the difference between a 160 degree and a 180 degree thermostat
> besides 20 degrees? i.e. which should be used when? And when I went to
> change mine, I found that the DPO didn't have one installed. Is this
> indicative of overheating problems?
>
The thermostat sets the minimum temp of the coolant in your system. It blocks
the flow through your radiator until the temp hits the set point, then releases
flow. Your operating coolant temp will therefore be in a range between the
thermostat set point (the minimum), and the equilibrium temp of your system in
full flow (the maximum temp it stabilizes at). If the radiator is inadequate
or you have other problems the "maximaum" will be an overheat condition.
Thermostats have different setpoints for different seasons or other variables.
For instance, you may want a higher minimum in the winter, since the cold air
may keep a freeflow temp in the radiator too low to ever really warm the car
up; so you'd use a higher setpoint thermostat to keep the temp up to that
desired minimum. In summer you have a different situation, with hot ambient
air taxing the system's ability to dump heat even in the freeflow condition, so
then you might use a thermostat that opens earlier to get it into freeflow
quicker, although this isn't as big a help as most people think -- if you're
overheating, and the thermostat is an ok type for the car, you really have a
malfunction or radiator/flow problem.
Some people remove the thermostat entirely in the summer for the above reason,
or because they can be unreliable and stick closed, causing overheating. DON'T
do this unless you know what you're doing! Removing the thermostat can change
the coolant flow pattern and cause localized overheating (hot spots) at various
places in some engines. If you are determined to remove the thermostat at
least put a gutted one in there to keep the flow pattern close to the original
design. Also, if your car has a water choke, using too cold a thermostat or
removing it may cause choke malfunction, if the coolant never reaches the
choke's trip temperature. If this happens your choke might stay on all the
time.
Best bet is to keep your system in good shape and use a good quality thermostat
in the manufacturer's suggested range. If you have a water choke use a
thermostat on the high side of the suggested range, to make sure your choke is
turning off. Besides, car engines run more efficiently at higher temps anyway
(within reason, of course!).
===
Michael B. Dietsche, P.E.
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