DeTomaso Mailing List: July 2001, Message #305

Chuck,

I found these portions of your message below to be especially
intriguing/puzzling/troubling, and so will respond.

Also, Does the water pump create pressure on one side, or vacuum on the
> other ?

This is one of many things that would be easy enough to measure but no one
(myself included) takes the time to do it.  However, I would point out that:

The block and heads are between the water pump and the water outlet on the
pressure side, so the pressure coming out of the water pump has to be higher
than that coming out of the water neck and into the header tank.  This seems
to be lost on a lot of people.  If the water pump pumped directly into the
radiator, I'd expect you'd blow up the radiator pretty quickly.  Also, the
suction hoses I've encountered usually if not always have a spring inside
them, so they don't collapse from the suction.

Additionally, I recently added some valves to my heater hoses, not because I
wanted to have valves necessarily, but because I needed something to take
the place of that H-pipe that the EGR vacuum switch goes into.  To check
that I had the valves oriented correctly with respect to the flow direction,
I let the engine idle and opened each valve.  There was impressive suction
on the suction hose, it sucked in a big gulp of air when opened.  The valve
on the pressure hose, of course, shot out a healthy blast of coolant when
opened.

So I conclude the suction side can go below atmospheric pressure, and even
with the radiator cap removed (atmospheric pressure at the tank), the
pressure at the water pump going into the block must be higher than
atmospheric.

 >
> I'll take just one component:
> If the pressure (remember air compresses, coolant basically does not), is
> greater
> in the swirl tank (main tank, or whatever you like to call it) because the
> water pump
> is right there ....

The compressibility of the air, you're confusing me here.  Both the air and
the coolant at any point, or in close proximity, are at the same pressure.
That is, a pressure/vacuum gauge will read the same whether measuring air or
coolant.  So I'm seeing this compressibility of the air as no factor.  Do
you see it differently?


then one expects that coolant will travel from the high
> pressure side,
> to the low (flow to the radiator).  I believe this only displaces coolant,
> not air.

Not clear to me why you would expect air, under pressure, to not move toward
another point of lower pressure.  Clarify?

Guy D.

----- Original Message -----
From: Chuck Melton <Melton01@email.msn.com>
To: Multiple recipients of list <detomaso@realbig.com>
Sent: Wednesday, June 27, 2001 12:23 PM
Subject: Re: Cooling


>
>
> > Richard, Chuck, et al,
> > Where does the idea that air cannot go "downhill" in a tube come from?
> > Example 1:  "blah blah blah"...
>
> ---Well Guy...that me start with this example.... I had believed, based
> upon
> my common sense only, that a top/bottom divided radiator would provide
> better cooling, than a front/back split radiator.
> I based this on the belief that the back half would have a smaller thermal
> differential (air to coolant).  I presumed therefore that a top/bottom
> split
> 2-pass radiator would be more efficient.
> My other cooling 'given' was that the more time coolant is in the radiator
> the farther the temp would drop, and the more efficient the radiator would
> be.
> ...It took some time, and sound logic for Richard Barkley and others to
> convince me that, as far as the second 'given' goes, that the system must
> be
> considered in whole, and coolant making 2 passes thru the complete
> cycle (engine/radiator) reduces heat better than the coolant staying in
the
> radiator
> for the same time, but during one 'visit'.
> As for the front/back versus top/bottom split, I didn't receive the
> polynomial
> equations, to prove one or the other, but since Richard and others
'seemed'
> correct on other matters, well I went along on the leap of faith.  I'll
> wait for
> a verified answer.
>
> The point of this, is that thru logic and reasoning, my opinion changed,
> and more
> importantly, I acknowledged this, by re-writing (correcting ???) my
cooling
> article.
> Old dogs CAN learn new tricks !
> The big value here, and my goal, is that anyone reading my webpage gets
> 'truth'.
>
> With that said, to convince me of the validity of this "bleed hose"
design,
> I'd like
> to see several aspects considered.  First, the point is made that a
> pressure
> differential does exist in the coolant system....or no flow would occur.
> Let's call that a 'given' and move on...
>
> Next, examine the purpose of this bleed hose.  Does it function to pass
air
> back ?
> Or coolant forward to the radiator ?  OR in some conditions one way, and
ot
> her
> times the other ?  (Is it intended to work with the engine off  or running
> ? both ?)
> (Does it work differently when hot versus cold ?)
>
> Also, Does the water pump create pressure on one side, or vacuum on the
> other ?
>
> I'll take just one component:
> If the pressure (remember air compresses, coolant basically does not), is
> greater
> in the swirl tank (main tank, or whatever you like to call it) because the
> water pump
> is right there ....then one expects that coolant will travel from the high
> pressure side,
> to the low (flow to the radiator).  I believe this only displaces coolant,
> not air.
> Therefore this 'duplicate' hose provides no air bleed benefit.
>
> It's too bad there are too many variables (yet to be netralized) to
> empherically
> test the various hypothii.
>
> You are not done with this topic, so save the Flat-Earth Society topic for
> later.
> I've sent this to the list, so other's (Who are NOT COMPLETEY BORED with
> this) can be amused or chime in !
>
> I await your valued discourse, but remember I am more
> convinced by the depth of your logic
> than the height of your conviction !
>
> Chuck
> Chuck
>
> >
> > Next let's debate if the world is flat or round.  I have dibs on round.
> >
> > Guy D.
>
>
>