Check for external leaks:  Usual areas of leakage are water manifolds, radiator seams, water pumps, freeze plugs and all hose connections.  The condition of radiator hoses should be carefully scrutinized for possible deterioration from age and/or wear from rubbing against accessory brackets, etc.  Be aware that in many cases radiator hoses wear from the inside out, so outside appearance can be deceiving.

Check for internal leaks:  Pull the oil dipstick and check for evidence of coolant.  It will show up as minute droplets or sludge and should be easy to spot.  This could indicate a cracked head, block or blown head gasket.

Check the radiator:  This is the one component in your vehicle's cooling system which can quickly diminish the efficiency and durability of the engine.  Check for obstructed air flow and clean any debris from the fins.  Also check the radiator mounting for loose bolts or cracked brackets from vibration and stress.

Check the Cooling fan:  If the vehicle is equipped with a centrifugal thermo-static type fan clutch, it is important to spot problems before they occur.  Check for wear by moving the fan blade back and forth.  Over 1/4" of play in either direction could point towards excessive bearing wear.  You should also turn the fan by hand.  If it free-wheels or there is a rough grating feel as the fan turns, this could mean excessive fluid loss or bearing wear respectively.  If any of these conditions exist or there is evidence of fluid leakage, the fan clutch should be replaced.  If the vehicle is equipped with an electric cooling fan, a quick performance check can be bade by turning on the A/C and checking to make sure it operates without excess vibration or noise.  Also check all electrical connections for signs of corrosion, or physical damage.  With the engine hot, check to see if the fan is coming on at the correct temperature and operating properly.

Check the coolant level and conditions:  Use an antifreeze tester to determine the protection range of the coolant.  It should be at least adequate for the geographic area where you live.  If the coolant is over 2-4 years old or has rust in it, system flushing and refilling with new antifreeze solution is recommended and will be sufficient for most climates.  The 2-4 year replacement interval is necessary to maintain proper rust inhibitor and other additive protection in the cooling system.

Check the radiator cap:  If your cap is rusted or the rubber seal is dried out, it should be replaced.  A pressure tester should be used to be sure the cap is operating at the recommended pressure level.

Check the thermostat:  Remove the radiator cap and start the engine.  Insert a suitable thermometer into the radiator neck.  When the coolant level drops in the radiator, the thermostat has opened and is allowing circulation.  Record the temperature on the thermometer and compare to the thermostat specifications.  It should be no more than a few degrees either way of the actual thermostat setting.  If you are not in the correct range, the thermostat will have to be replaced.  Be sure to install a new gasket and inspect the thermostat seating area for corrosion and pitting.

Check drive belts:  Visually inspect all belts for glazing or deterioration.  These conditions usually are caused by wear but can be accelerated by improper adjustment, engine fluid spillage, lubricant leakage or improper belt sizing.  Check the vehicle manufacturer's specification listing for proper belt size, tension and/or deflection specifications.

Check heater operation:  A quick functional testing of the heater unit can save a lot of mid-season grief.  Visually inspect all hoses for deterioration from age and wear.  Check the floor under the heater assembly for signs of coolant loss.  This could point towards a leaking heater core.  Also make sure to check the heater valve.  Check vacuum lines for leakage or deterioration.  Lubricate all control cables, such as the heater valve control cable, etc.  Last but no least, check all function switches and blower motor switches for proper operation.  Having basic cooling system checks made during routine servicing can prevent costly breakdowns and inefficient operation of equipment during extreme climate conditions.  Preventive maintenance is the key to being able to drive your car longer while reducing long term expenses.

Here's why. The cost of overhauling an engine can run into thousands of dollars; automatic transmission repairs also are expensive and cooling system neglect could be responsible.

A cooling system performs several functions: (1) it must keep the engine running within specified temperatures, not too hot and not too cold; (2) it cools the automatic transmission and, lest we forget, (3) it circulates hot water through the heater.

Temperatures inside an engine may soar to 4,500 - 5,000 degrees F., enough to melt an engine block in a matter of minutes if it were not for the cooling system.

Over the years there have been numerous developments that make it harder for the cooling system to perform theses tasks. Today's engines run much hotter than in years gone by. Added emission control systems, smaller radiators and crowded engine compartments add to the challenge.

To avoid problems resulting from rust, dirt and mineral deposits in the cooling system, it's best to give it an internal cleaning every three to four years.