Re: alfa-digest V7 #51RE: Overheating coolant

[Rodney Tidwell <rodneygt@xxxxxxxxxxx>]

FERDINANDO DI MATTEO wrote:

> I'm surprised at how many of you have no idea what the purpose of the
> coolant thermostat is.  Reasons for overheating are many and guessing
> solved nothing.  I shall try to tell you what I've learned about the
> thermostat.  It is there to regulate the flow of coolant through the
> engine and radiator.  If the coolant flows too fast through the
> radiator, it cannot lose enough heat before it gets heated some more
> with each pass.  An engine, any engine, depending on a radiator to
> cool
> its coolant will overheat very badly with thermostat removed.

Mr. Di Matteo,I normally would not take issue with what you say.  Your
freely offered knowledge has been of great benefit to me over the years
as I've tried learn something of Alfas.  However, as I'm apparently one
of those people who "have no idea what the purpose of the coolant
thermostat is", I decided I'd relay my thoughts.

I drove my milano for three weeks w/o a thermostat (approximately 100
miles/day).  The car did not overheat.  To the contrary, the needle on
the temperature gauge would barely rise.  Without a thermostat, the
temperature would peak at around 120 F (summer).  With a thermostat the
operating temperature was around 175 F.

As another case in point, an acquaintance had bought a used suburu.  It
ran very cold.  When winter arrived, he was complaining that he didn't
think the heater would work very good.  I told him someone had removed
the thermostat.  Sure enough, I took the water neck off and there was no
thermostat.  I put in a new thermostat and the engine would then run
much warmer.

I've seen many vehicles with the thermostats removed and not one had an
overheating problem.

As you noted, coolant that flows through the radiator faster does, of
course, exchange less heat.  But, coolant that flows fast through a hot
engine, likewise, picks up less heat per unit.  It's a sort of trade
off.  One would actually expect some sort of equilibrium; that is, the
engine would eventually run the same temp with or without the
thermostat. But, of necessity (probably optimum engine performance), the
thermostat requires the engine to run hotter than it would "naturally".
That is, the thermostat will only lets cooled coolant into the engine's
water passages in relatively small amounts.

Relatedly, a "colder" thermostat does not open (or allow coolant flow)
later, it opens earlier. When a car overheats due to a bad thermostat,
it's not because it's stuck open.

I, of course, await edification.  But, my experiences are undeniable.

Rodney G. Tidwell
McComb, MS

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