See Figures 1 through 12
Dealing with the cooling system can be a dangerous matter unless the proper precautions are observed. It is best to check the coolant level in the radiator when the engine is cold. On early models this is accomplished by carefully removing the radiator cap and checking that the coolant is within 2 in. of the bottom of the filler neck. On later models, the cooling system has, as one of its components, a coolant recovery tank. If the coolant level is at or near the "FULL COLD" line (engine cold) or the "FULL HOT" line (engine hot), the level is satisfactory. Always be certain that the filler caps on both the radiator and the recovery tank are closed tightly.
In the event that the coolant level must be checked when the engine is hot on engines without a coolant recovery tank, place a thick rag over the radiator cap and slowly turn the cap counterclockwise until it reaches the first detent. Allow all hot steam to escape. This will allow the pressure in the system to drop gradually, preventing an explosion of hot coolant. When the hissing noise stops, remove the cap the rest of the way.
If the coolant level is found to be low, add a 50/50 mixture of ethylene glycol-based antifreeze and clean water. On older models, coolant must be added through the radiator filler neck. On newer models with the recovery tank, coolant may be added either through the filler neck on the radiator or directly into the recovery tank.
The radiator hoses and clamps and the radiator cap should be checked at the same time as the coolant level. The radiator cap gasket should be checked for any obvious tears, cracks or swelling, or any signs of incorrect seating in the radiator filler neck.