Oldsmobile 1999 Alero - Manual (Page 211)

yellow blue
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4. With the coolant surge tank pressure cap off, start the
engine and let it run until you can feel the upper
radiator hose getting hot. Watch out for the engine
cooling fans.
By this time, the coolant level inside the coolant
surge tank may be lower. If the level is lower, add
more of the proper mixture to the coolant surge tank
until the level reaches the FULL COLD mark, or just
above the small cylinder at the base of the opening.
5. Then replace the pressure cap. Be sure the pressure
cap is hand - tight.
Check the level in the surge tank when the cooling
system has cooled down. If the coolant isn’t at the
proper level, repeat Steps 1 to 3 and reinstall the
pressure cap or see your dealer.