Honda 1991 Prelude Owner's Manual page 92

If the level is between the MIN and MAX marks on the dipstick
add a 50/50 solution of antifreeze and water to bring it up to MAX.
If there is no coolant visible on the dipstick, the cooling system
should be checked for teaks and repaired if necessary. Coolant
must then be added to the radiator.
CAUTION:
Radiator coolant will damage paint. Quickly rinse any spilled
coolant from painted surfaces.
Wait until the engine is cool, then turn the radiator cap counterclock-
wise until it stops. DO NOT PRESS DOWN WHILE TURNING THE
CAP. After any remaining pressure has been relieved, remove the
cap by pressing down and again turning it counterclockwise. Add
enough coolant to fill the radiator, and reinstall the cap. Be sure to
tighten it securely. Fill the reserve tank up to the MAX mark with
the engine cold.
Maintenance
1. Check the freeze protection level of the coolant with a hydrome-
ter.
2. Keep the front of the radiator free of dirt and debris.
3. Check hoses and hose clamps regularly.
RESERVE TANK
MAX
MIN