There are always places in the system where air gets trapped until the
engine is run so that's why the level drops. Of course needs to get to
temp up to open the thermostat to the radiator of course. Then the
pressure has to open the radiator pressure cap.
On my Ford Contour I once watched this happen and it sucked it all in in
a big whoosh. I was having a water pump and heating problem at the time.
Normally on the Spitfire I simply run it a bit and top up and repeat a
couple of times when I have drained the system. Make sure it's cold when
you top it up. Normally I don't even let it run more than a few seconds
as that's enough to get the water moved around the system and the air to
the top of the radiator and check that level and that the bottle is
always half full.
Alan
Andrew Beck wrote:
>1979 Triumph Spitfire
>
>Just finished installing a new water pump and getting everything back
>together. My Haynes manual says to full the radiator up to the top, also
>fill the expansion bottle up to the top. Then let the car run at about
>1000rpm. Then if the expansion bottle drops below half, refill....
>
>This doesn't make sense. Why would I want the expansion bottle to be full?
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