For a gas to move from one point to another, it has to
be moving from a region of relatively higher pressure
to a region of lower pressure. Basicaly the water pump
adds pressure to the system, and the friction of the
fluid against the passage walls throughtout the
remainder of the system reduces the pressure. The
point of lowest pressure is going to be right before
the input of the water pump. I would look at the hose
between the radiator and the input to the water pump.
If it's not combustion gasses, it has to be atmospheric
gas, which is typicaly at a lower pressure than the
water in the cooling system, and not likely to enter
the system at very many other places. There are also
issues surrounding the relative hights of the
filler-neck and the input to the water pump.
I don't see how block porousness has anything to do
with it. Even if the mechanic was talking about pores
between the cooling jacket and the outside world (as
opposed to the cylinders), the pressure differential
would not support that. Speaking of which, do you have
the proper pressure-rated radiator cap in your system?
James J.
On Tue, 10 September 2002, "Telewest \(PH\)" wrote:
>
> I was describing to a well-known engine builder
> problems I was having with
> my factory V8 cooling system pumping up with air. I
> described how I had
> tested the coolant for combustion gases as I suspected
> head gasket but that
> came up negative. He suggested the block might have
> become porous. Two
> things strike me here - I had already said there was
no
> combustion gases in
> the coolant, and doesn't the allow block have steel
> sleeves in the bores?
> Am I missing something or is he?
///
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