-------------- Original message --------------
From: "Klebert L. Hall" <crocuta@xxxxxxxxxxx>
> > Subject: Re: IML: thermostats
> > From: PAUL WENTINK
> >
> > I don't understand how the lower temperature thermostat is going to
> > cool down a hot engine. Once its hot, the only way to cool it down
> > is
> > to turn it off and wait. Sitting in traffic with it running will only
> > make it hotter since there is less air and water circulation under
> > stop
> > and go conditions.
>
> You're right, it doesn't help at all once the engine is hot.
>
> Here's the circumstance where I've found it helps:
>
> I'm driving along the highway at 70 or 80mph on a hot day, with the
> A/C on - the car is running in proper temp conditi on, so the coolant is
> around the thermostat temp, and the thermostat is opening and closing
> periodically.
>
> I then get off the highway (and probably turn off the A/C
> temporarily). I have to slow down, or enter stop-and-go traffic, so the
> engine temp starts to climb. It will eventually cool down, as the
> cooling system catches up with the big heat dump from the lower airflow
> (presuming it isn't overwhelmed and overheats), but right now it's
> climbing.
>
> If the thermostat is a 160, the temp starts climbing from the
> vicinity of 160 and has about 90 degrees until it gets to the boil-over
> imminent range around 250. If it's a 180, it starts around 180, and only
> has 70 degrees to go.
>
> Thus, the lower temp thermostat gives a bigger time and temperature
> 'cushion', in which the cooling system has a chance to catch up.
>
> -Kle.
&g t; '69 Crown 4DHT (resting)
>
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