Honda 1999 Odyssey Owner's Manual page 239

Cooling System
RADIATOR CAP
1. Make sure the engine and radiator
are cool.
2. Turn the radiator cap counter-
clockwise, without pressing down
on it, until it stops. This relieves
any pressure remaining in the
cooling system.
3. Remove the radiator cap by
pushing down and turning
counterclockwise.
Maintenance
RESERVE TANK
4. The coolant level should be up to
the base of the filler neck. Add
coolant if it is low.
5. Put the radiator cap back on.
Tighten it fully.
6. Pour coolant into the reserve tank.
Fill it to halfway between the MAX
and MIN marks. Put the cap back
on the reserve tank.
Do not add any rust inhibitors or
other additives to your vehicle's
cooling system. They may not be
compatible with the coolant or
engine components.