[ROVERNET - UK] P6B Expanison tank

[Gavin.Walker at csiro.au]

As coolant heats up it expands.  Back in the time of radiators with top
mounted header tanks this meant no matter how often you filled it you
would always have air in the header tank.  That's ok.

However with the advent of cross flow radiators with side mounted header
tanks this air ended up in the top few centimetre of the radiator.  So
this section of the radiator isn't contributing significantly to
cooling.  The solution is to fit either an overflow bottle or an
expansion tank.

An overflow bottle is just a catcher for the coolant that overflows
through expansion.  When the radiator cools down it sucks the coolant
back in so the radiator is always full.

An expansion tank is an extension of the radiator.  It's equivalent to
putting a header tank on top of the cross flow radiator.  So instead of
having air in the top few centimetres of the radiator there's air in the
top half of the expansion tank.

For what it's worth, I have a stock looking cross flow TC radiator that
has what looks like a factory expansion tank on the side.  I've also
fitted overflow bottles from other cars to P6 radiators.

Gavin Walker
Canberra, Australia