Subject: [TR] Over heating

From: Cosmo Kramer <[email-masked]>
Date: Sat, 16 Mar 2013 07:32:34 -0700 (PDT)

Hi List!
In digest 6:94 Randall wrote:
I initially installed the stock fan and
radiator on TS13571L (except the radiator had no crank hole, so I'm assuming
the previous owner had it recorded).  It worked great under most conditions,
but coming home from TRfest 2009 I found a big traffic jam where we averaged
under 20 mph for roughly 40 miles.  (Yes, that's over 2 hours stuck in
traffic.)  The gauge kept slowly creeping up, until I started shutting the
engine off every chance I could, to keep the heat down.  That was when I
determined to go back to the electric fan I had used on the previous TR3A.
----------------------------
I was told that shutting the engine off  & then
starting it up to move, to keep the heat down would INCREASE the chance of
over heating because starting the engine causes more heat. Now I don't
understand why, but that's what I was told (not saying that I believe that).
 
Can any explain WHY this might happen?
-Cosmo Kramer

** [email-masked] **

Archive: http://www.team.net/archive

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From: "Randall" <[email-masked]>
Date: Sat, 16 Mar 2013 09:18:10 -0700

> I was told that shutting the engine off  & then starting it 
> up to move, to keep the heat down would INCREASE the chance 
> of over heating because starting the engine causes more heat. 
> Now I don't understand why, but that's what I was told (not 
> saying that I believe that).

Stopping the engine after it has been working hard (for example driving at
normal freeway speeds) can cause the coolant temperature to rise.  The metal
of the engine is hotter than the coolant, and once the engine is shut off,
the heat doesn't get moved to the radiator.  So the coolant temperature goes
up as heat moves from the metal into the coolant.

Starting does not generate any extra heat, except of course that the engine
generates some heat whenever it is running.

But in my case, the engine was not working hard at all.  I use very little
throttle even when traffic starts to move.  So "heat soak" (as the above
effect is called) was not an issue.  And the brief periods with the engine
not running reduced the overall amount of heat produced.  I was able to not
only stop the slow rise of the temperature gauge, but get it to come back
down some.  Revving the engine up as Bill suggested did not seem to help at
all (probably has something to do with the extra heat generated by revving
the engine up).

Your mileage may vary and all that.  But I've used my technique many times
over the years and it does work.  I even once drove a few months in Indiana
summer (with a previous TR3A) with no radiator fan at all; just by turning
the engine off every time I knew I was going to stop (coming up to a stop
sign or seeing the light turn yellow).

Now with the electric fan, it's simply not an issue.  The needle goes to 185
and stays there, even in heavy traffic.  Coming home from work last night
was just a smallish traffic jam, but I'd guess it took 30 minutes to cover 9
miles and the gauge never even reached the '5' in '185'.

-- Randall