Checking The Radiator Cap
While you are checking the coolant level, check the radiator cap for a worn or cracked gasket. If the cap doesn't seal properly, fluid will be lost and the engine will overheat. Worn caps should be replaced with new ones.
Clean Radiator Of Debris
Any time you have the hood open, glance at the coolant recovery tank to make sure it is properly filled. Top off the cooling system using the recovery tank and its markings as a guideline. If you top off the system, make a note of it to check again soon. A coolant level that consistently drops is usually a sign of a small, hard to detect leak, though in the worst case it could be a sign of an internal engine leak (blown head gasket/cracked block-... check the engine oil for coolant contamination). In most cases, you will be able to trace the leak to a loose fitting or damaged hose (and you might solve a problem before it leaves you stranded). Evaporating ethylene glycol antifreeze will leave small, white (salt like) deposits, which can be helpful in tracing a leak.
At least annually or every 15,000 miles (24,000 km), all hoses, fittings and cooling system connections should be inspected for damage, wear or leaks. Hose clamps should be checked for tightness, and soft or cracked hoses should be replaced. Damp spots, or accumulations of rust or dye near hoses or fittings indicate possible leakage. These must be corrected before filling the system with fresh coolant. The pressure cap should be examined for signs of deterioration and aging. The fan belt and/or other drive belt(s) should be inspected and adjusted to the proper tension. Refer to the information on drive belts found earlier in this section. Finally, if everything looks good, obtain an antifreeze/coolant testing hydrometer in order to check the freeze and boil-over protection capabilities of the coolant currently in your engine. Old or improperly mixed coolant should be replaced.
At least once every 3 years or 36,000 miles (48,000 km), the engine cooling system should be inspected, flushed and refilled with fresh coolant. If the coolant is left in the system too long, it loses its ability to prevent rust and corrosion. If the coolant has too much water, it won't protect against freezing.
If you experience problems with your cooling system, such as overheating or boiling-over, check the simple before expecting the complicated. Make sure the system can fully pressurize (are all the connections tight/is the radiator cap on properly, is the cap seal intact-). Ideally, a pressure tester should be connected to the radiator opening and the system should be pressurized and inspected for leaks. If no obvious problems are found, use a hydrometer antifreeze/coolant tester (available at most automotive supply stores) to check the condition and concentration of the antifreeze in your cooling system. Excessively old coolant or the wrong proportions of water and coolant will hurt the coolant's boiling and freezing points.
Periodically, clean any debris-leaves, paper, insects, etc.- from the radiator fins. Pick the large pieces off by hand. The smaller pieces can be washed away with water pressure from a hose.
Carefully straighten any bent radiator fins with a pair of needle-nosed pliers. Be careful; the fins are very soft. Don't wiggle the fins back and forth too much. Straighten them once and try not to move them again.