Is your water dissapering into the expansion bottle, or just dissapering
altogether.
It it's goes in to the bottle and dosent return there might be a leak in
your cooling system which only shows it's self when your car is cooling.
i.e. in stead of sucking the water back from the bottle it's sucking air
instead.
Things which would do this are:
A hole in the water pipe radiator to bottle. (i.e. hole in the straw)
Bad seal on one of the hoses which just happens to seel under positive
pressure, but not negative.
Real old and week hoses which cave in instead of sucking the water back up.
(you can tell this by the radiator making a sucking sound when you open it
after it has cooled).
A bad seel on the top seel of the radiator cap.
The return valve (metal bit in sprung onto the smaller lower rubber seel of
the cap) is blocked or dosent opperate.
It it's just dissaperaing, check for leeks, get the engin realy hot between
1/2 and 3/4 on the gadge, (paper on rad) and for drips. (remember to remove
paper before you get too close, and run the car to cool it down, don't turn
it off when it's hot or you'll get boil over, keep that water moving).
You may have a blown head gasket if it's none of the above, on the Spitfire
this may do damage if you are REALY unlucky, but I have had it happen 5
times (before I chainged to better quality cylinder head nuts) and no damage
was done. Anyway with the head off, you can do a decoke and lap the valves.
As for advice on cooling, if you were about to melt a main bearing, you had
somthign a bit more wrong than a dodgy cooling system. The 1500 especialy
need an oil cooler which should have been fitted as standard to all moddels,
the oil is what gets rid of a high perportion of the heat from the engin.
I use the highest temperature thermostat in my Spitfire, it meens that it
will never get cooler than 1/2 unless a lot of heat is being lost through
the heater, lower temperature thermostats will open sligtly below 1/2.
Above 1/2 way and all the thermostats provide equal cooling, i.e. if your
car gets to 3/4 mark with the 82 degree themostat, then it will get to 3/4
with the 78 (albeit slightly slower because it will take a while to get from
the valve opening temperature to 1/2 way).
My car is currently suffering from an in effective water pump, i.e. it doent
force water around the radiator that well. When I am in traffic the block
gets hot, but the pump dosn't get the water too the radiator that quick.
But when I start to go or I turn on the electric cooling fan, the
thermosyphon starts up and gets all the hot water out of the block and into
the radiator. This causes a momentery increese in temperature, before it
plumets to 1/2.
I don't have an engin driven fan, but anything above 30 mph and I get enough
air to keep it as cool you like. If I leave the electric fan on all the
time I rely on the 82 deg thermosat to keep the engin from getting too cold
and me having to use choke. If I ran the car without the thermostat, and
the electric fan on I would need choke amost all the time. In built up
areas I will turn on the fan as a matter of course, only because the bad
water pump means that the fan won't come on until the block is over 3/4 and
nearly at MAX. Even though the fan is set to come on just half way to 3/4.
Anyway thers enough info there for you to work out whats wrong
James
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