Date:         Thu, 27 Dec 2007 12:17:22 -0500
Reply-To:     Allan Streib <streib@CS.INDIANA.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Allan Streib <streib@CS.INDIANA.EDU>
Subject:      Re: Overcooling Hypothesis--Long
Comments: To: Geza Polony <gezapolony@SBCGLOBAL.NET>
In-Reply-To:  <vanagon%2007122711451825@GERRY.VANAGON.COM> (Geza Polony's
              message of "Thu, 27 Dec 2007 11:43:57 -0500")
Content-Type: text/plain; charset=us-ascii

Geza Polony <gezapolony@SBCGLOBAL.NET> writes:

> Here's my idea. When you're coasting downhill, you're using the
> engine as a brake. This means that above 1500 RPM, with the idle
> switch closed, the engine isn't getting any gas, as the ECU has shut
> the injectors down. If it isn't getting any gas, it also isn't
> producing any heat. The engine is functioning as a brake, but there
> isn't any combustion, and so, after a period of 10 minutes or so in
> freezing temperatures, the coolant loses temperature, and your gauge
> is way off the edge of the scale.

Makes sense.  Not only is there no combustion but you are flushing
cold outside air through the cylinders, which has a further cooling
effect.

> I tested this by going downhill, engine warm, and taking my foot off
> the gas to coast. I could see the gauge move colder before my
> eyes. Give it a little gas, and the engine warms up. This is kind of
> tricky from a driving standpoint, but it works.

Now, repeat the experiment with the clutch in, so the engine is
idling, not being overrun.  See if it stays warmer.

Allan