Vauxhall ASTRA Owner's Manual page 302

Antifreeze and corrosion protection
Before the start of winter, have a workshop
check the antifreeze protection. The
antifreeze level must guarantee protection
to approx. -28 °C. Insufficient antifreeze
will reduce the frost protection level and
the corrosion protection. If necessary add
antifreeze.
If coolant loss is topped up with water,
have concentration checked and add
antifreeze if necessary.
Coolant level
Hardly any losses occur since the cooling
system is sealed and it is thus rarely
necessary to top up the coolant.
The coolant should be a little above the
KALT/COLD mark in the expansion tank
with a cold cooling system. The coolant
level can also be read off from the outside
of the expansion tank.
9
Warning
Allow engine to cool down before
removing coolant filler cap. Remove filler
cap carefully so that pressure can escape
slowly, otherwise there is a risk of
scalding.
Service, maintenance
When the engine is at operating
temperature, coolant level rises. It falls
again when the system cools. If it falls
below the KALT/COLD mark when the
system is cold, top up to just above the
mark.
Top up antifreeze. If no antifreeze is
available, top up with clean tap water. If
tap water is unavailable, distilled water
can be used.
After topping up with water or distilled
water, check the antifreeze concentration
and add antifreeze if necessary. Have a
workshop eliminate the cause of the
coolant loss.
Too low a coolant level can cause engine
damage.
To close, position the cap and screw it into
place.
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