Honda 2003 Civic Hybrid Owner's Manual page 267

If Your Engine Overheats
9. Using gloves or a large heavy
cloth, turn the radiator cap
counterclockwise, without pushing
down, to the first stop. This
releases any remaining pressure in
the cooling system. After the
pressure releases, push down on
the cap and turn it until it comes
off.
Start the engine and set the
10.
temperature control dial to
maximum. Add coolant to the
radiator up to the base of the filler
neck. If you do not have the
proper coolant mixture available,
you can add plain water.
Remember to have the cooling
system drained and refilled with
the proper mixture as soon as you
can.
270
Taking Care of the Unexpected
11. Put the radiator cap back on
tightly. Run the engine and watch
the temperature gauge. If it goes
back to the red mark, the engine
needs repair. (See Emergency
Towing on page 282 .)
12. If the temperature stays normal,
check the coolant level in the
radiator reserve tank. If it has
gone down, add coolant to the
MAX mark. Put the cap back on
tightly.