Alistair, while I agree that chemical environment matters to chemical processes, I am not sure that the facts you cite would prevent precipitation of suspended matter in a static setting with tiny passages.  But, I (like others) have been wrong before.  mcneely

---- Alistair Bell <albell@SHAW.CA> wrote:
> Dave,
>
> the comparison you make between a car's cooling system:
> - closed loop, low O2 (if not anoxic), water, ethylene glycol, corrosion inhibitors
>
> and a dishwasher:
>  - open loop, O2 rich, water, caustic cleaning solution
>
> doesn't warrant much more thought than just how bad an analogy you made .
>
> :)
>
> alistair
>
>
> On 2012-11-19, at 7:09 AM, <mcneely4@cox.net> <mcneely4@cox.net> wrote:
>
> > I apologize in advance for anyone who is bothered by pedantry.  You don't have to read it.
> >
> > Of course you are correct, Alistair.  But, embedded in the imprecise language is a kernel of value.  When a solution like coolant, which has a higher viscosity than does water, and may also contain some materials leached or eroded from various metal components of the coolant system, sits in a stagnant state, it is more likely to precipitate some of those materials creating a greater likelihood of plugging small passageways than when it is flowing.
> >
> > I clearly demonstrated this when I had a pump go out on a dishwasher just when I was leaving for a three week trip.  I just left the water, with detergent and crud in it, in the dishwasher.  When I returned, I had to replace more than the pump.  The screens and chopper blade were plugged and had to be replaced as cleaning them did not work, though I used a concentrated citric acid solution.
> >
> > BTW, what is usually called a knob in mechanical applications where it serves as a handle to transfer a circular motion is in fact a kind of lever.  An easy way to visualize this is to imagine that a door knob is reduced to a rectangular piece running across its diameter.  Then cut off one radius of the piece.  What you have is a lever such as has become popular for home doors to reduce strain on hands and wrists of older folks.  Many knobs are constructed with a rectangular piece running across one diameter to serve as a handle to make grasping easier.  That in fact is what the valve on the rear heater has.  This also demonstrates the fact that a knob is simply a lever acting to apply torque.
> >
> > mcneely
> >
> > ---- Alistair Bell <albell@SHAW.CA> wrote:
> >> "old coolant is terribly corrosive"
> >>
> >> come on now, how is coolant that is not circulated any older than the stuff that is circulated. I call bull-pucky.
> >>
> >> alistair
> >>
> >> On 2012-11-18, at 1:50 PM, Scott Daniel - Turbovans wrote:
> >>
> >>> There is no 'control knob' ..
> >>> there is a lever that you can reach with your fingers, through a hole in
> >>> the rear heater cover.
> >>>
> >>> if the cover is not in place...the poster could be looking at a
> >>> knob-like thing ..the bleed valve.
> >>>
> >>> Bentley would not say much about this leverthat regulates coolant flow .
> >>> but the van's Owner's Manual sure does.
> >>>
> >>> 'Forward' on the lever is 'on'.
> >>> Aftward is off.
> >>>
> >>> I recommend having it at least mostly 'on' all year ..
> >>> as having no flow at all, ever, or for very long periods ,  contributes
> >>> to rear heater core leaking ..
> >>> a pretty common thing actually. .
> >>>
> >>> Whether warm air comes out the rear heater is determined by the fan for
> >>> the rear heater being on or not, or course.
> >>>
> >>> you always want at least some coolant flowing through the rear heater so
> >>> some fresh healthier coolant is always going through it ...the parts
> >>> last longer that way.  Old coolant is terribly corrosive.
> >>>
> >>> Nobody on this list of course...
> >>> there are lots of vanagon owners that don't know about the heater
> >>> control lever under the back seat.
> >>> I was kinda shocked actually to find out VW did it that way.
> >>> I can't think of one other car that has a partially heater control under
> >>> the back seat.
> >>>
> >>>
> >>>
> >>> On 11/18/2012 11:49 AM, Dave Mcneely wrote:
> >>>> Harry, that control allows coolant to circulate through the heater core.  Summer, off, winter, on.  To control air flow, use the knob on the dash.  mcneely
> >>>>
> >>>> ---- Harry Hoffman <hhoffman@IP-SOLUTIONS.NET> wrote:
> >>>>> Hi all,
> >>>> The heater under the rear seat has a control knob.
> >>>> Can someone tell me what it does? The Bentley only shows a picture but not how it functions.
> >>>>
> >>>> Cheers,
> >>>> Harry
> >>>>
> >>>> --
> >>>> David McNeely
> >>>>
> >
> > --
> > David McNeely
>

--
David McNeely