[Vwdiesel] Direction of coolant flow in radiator

[Erik Lane]

yeah, i saw that page in the bentley but assumed that
it could be in error. (and i think i mentioned it?)
looks like i was the one wrong. but i REALLY don't
like the design that way.

i have to ask - what does btdt mean?

the closed system and assuming all is well with the
expansion tanks is all well and good and would
probably be very reliable 95% or more of the time. but
what happens when a hose cracks or the radiator get
punctured? i believe in fail safe engineering and
pulling from the top of the radiator and planning on
it always being full and a perfectly closed system is
by all means *NOT* my idea of fail safe. even if the
engine starts to overheat due to lack of cooling, as
long as the engine is the LAST thing to run out of
coolant then there's some safety factor built into it.
i've lost a little of my confidence in german
engineering today. :(

yes, bleeding these monsters takes some patience. but
i've never had to prop them up. i just bleed the thing
out then drive it a few hundred yards and repeat.
never had it fail.

erik

--- Mary Beth and Chris Geiser <geiser at execpc.com>
wrote:

> I'm not saying how it "should" be - just passing on
> info: 
> The original set up for the Vanagon cooling system
> has coolant 
> enter bottom of the radiator and return out the top.
>  In
> addition to having BTDT, it shows this in Bentley on
> page 19.5.
> Sucking air is prevented as it is a closed system
> and must
> have air bled out after any coolant system work. 
> Read
> vanagon list archive and you see zillions of posts
> about 
> people trying to figure out how to get all the air
> out
> of that system.  Expansion tank is plumbed in to add
> coolant
> to return line if level drops slightly.  Then a
> second true "expansion"
> tank is present behind the license plate to catch
> overflow from
> heating / cooling...  My only guess as to why it's
> this way is to
> slow the coolant's flow through the radiator enough
> to let it cool while
> there?  Also, if coolant flowed in the top, it would
> be very hard to
> get air bled out of system I would think.  Could
> have solved a lot of
> problems by putting a true radiator cap on the
> radiator up front
> for filling.
> 
> Proper bleeding in my experience takes propping the
> nose up (way up
> if possible) and bleeding the air out the bleeder
> valve on the
> radiator, then propping the tail up and burping the
> first expansion
> tank a number of times.  Repeat propping each end
> once more if
> you're not convinced air is out.
> 
> Chris
> 
> -----Original Message-----
> From: vwdiesel-bounces at vwfans.com
> [mailto:vwdiesel-bounces at vwfans.com]
> On Behalf Of Erik Lane
> Sent: Thursday, September 02, 2004 10:18 AM
> To: LBaird119 at aol.com
> Cc: vwdiesel at vwfans.com
> Subject: Re: [Vwdiesel] Direction of coolant flow in
> radiator
> 
> as much as i respect your opinion, and i think that
> you have much more experience in these things than i
> do, but this time i think you're wrong.
> 
> if it were to pull from the top of the radiator then
> as soon as the coolant level were a little bit low
> then it would be sucking air. yes, it is a closed
> system, but if it were taking from the top of the
> radiator then the radiator would ALWAYS be full,
> until
> the time when the engine were completely empty of
> coolant. and the head of the engine would be the
> FIRST
> thing to be lacking in coolant. not a good recipe
> for
> an aluminium head.
> 
> i think that it would be VERY bad engineering to
> risk
> the engine in that fashion. ALL of the diesels i
> have
> worked on do not do that. if you look at the water
> pump you can see that it pulls from the radiator and
> pushes it into the engine block from there. tho i
> guess you could be right on the other wasserboxers
> cause i don't have first hand knowledge of them, but
> i
> still really doubt it.
> 
> erik
> 
> --- LBaird119 at aol.com wrote:
> 
> > 
> > > and i THINK every other car vw or not is the
> same.
> > if
> > > the water pump was trying to pull water from the
> > top
> > > of the radiator then if the water level were
> only
> > a
> > > little low then the pump would suck air and
> there
> > goes
> > > the engine overheating. so i HIGHLY doubt that
> any
> > > engine is set up that way.
> > > 
> > 
> >   Actually I think the rest of the VW's ARE the
> > opposite.  They go in the 
> > bottom and come out the top of the radiator.  Just
> > feel the hoses as you 
> > wait for the thermostat to open the bottom hose
> gets
> > HOT all of a sudden 
> > while the radiator is still cool.  It's a "closed"
> > system so the air is 
> > pushed 
> > out the small hose into the reservoir and the rest
> > goes into the head 
> > from the top of the rad.
> >      Loren
> > _______________________________________________
> > Vwdiesel mailing list
> > Vwdiesel at vwfans.com
> > http://www.audifans.com/mailman/listinfo/vwdiesel
> > 
> 
> 
> 
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