Summer can be the most challenging season for automotive cooling systems. Vacations with long drives to distant places means carefree time for car owners, but hard work for engines and cooling systems. In the summer, engines often hit peak operating temperatures due to stress from the air conditioning system and extended running times during long trips. The result can be overheating if the cooling system does not operate efficiently. The spring is the perfect time of year to check cooling systems, especially on cars brought in for tune-ups and pre-season air conditioner service.

Effective cooling system operation is probably more important today than ever. Each engine operates most efficiently within a certain temperature range, and the cooling system plays a key role in keeping the engine within range. As engines have become more sophisticated, temperature ranges have narrowed, and are expected to narrow further in the future.

Some of the current trends in cooling system repair and maintenance involve the water pump and coolant. Over the last few years, car manufacturers have been increasingly replacing gray iron water pumps on new cars with pumps that have aluminum or, in some cases, sheet metal housings. The new materials have proven to be effective and offer the advantage of weight savings. It is important to know that most of these water pumps are less expensive when purchased new but are more costly to recondition than gray iron pumps. Therefore, when it's time to replace one of these pumps, it usually makes more sense to install a new one instead of a reconditioned unit.

Low Silicate Antifreeze
A lot has been written about the role of silicates in antifreeze. Yes, they do help prevent corrosion of the internal aluminum components that are increasingly used in engines. But they also tend to drop out of solution to form solids. As a solid, they can clog the system or damage components such as water pump seals. Some vehicle manufacturers and component suppliers are now recommending low silicate antifreeze. Most get the job done using a limited amount of silicate. A way to further keep solids out of the cooling system is by using distilled water in the 50-50, antifreeze-water mixture. Many municipal systems add small amounts of solids, such as lime, to their water. These solids may serve a function in drinking water, but are best kept out of automotive cooling systems.

When adding fresh coolant mixture to a partially filled system, be certain the antifreeze type you are adding is the same as what is already in the system. In other words, never add propylene glycol based antifreeze to a system containing ethylene glycol antifreeze; and never add a low silicate antifreeze to a system containing a no silicate antifreeze.

Assuming the customer has not indicated any problems and you have not noticed anything out of the ordinary, a pre-season check of the cooling system is usually not time-consuming and involves mostly visual inspections of several primary components. Always have the engine off when performing these checks:

• Hoses - Radiator hoses deteriorate in normal use from flexing, vibration, high temperatures and chemicals in the coolant. Replace hoses that are cracked or brittle. Feel the hoses and replace any that are hardened or swollen, since they could fail at any time.
• Pressure cap - Not just a radiator cap anymore, it pressurizes the system, raising the coolant's boiling point to prevent overheating. Replace the cap if the gasket is cut or looks brittle. Check the spring with a pressure cap tester and replace the cap if it cannot hold the rated pressure.
• Coolant - Flush the cooling system any time the coolant appears contaminated. Be sure coolant is at the specified level.
• Drive belt(s) - Drive belts can become loose and slip, causing a variety of problems. They should be inspected and replaced regularly, as recommended by the manufacturer. Inspect by twisting each belt to expose the underside and look for glazing or fraying, fatigue cracks and other signs of deterioration. Replace belts with these symptoms. Belt tension should also be checked. Press down on the belt about midway between the pulleys. It should deflect from 1/2 to 3/4 of an inch. Caution: Over-tightened belts can cause water pump bearing damage. Use a belt tension gauge for a more accurate reading. Then adjust to spec.
• Fan blades - Look for cracks, bent blades and loose rivets. Never straighten a bent blade; instead, replace the fan. If the straightness of a blade is in question, remove the fan and lay it down on a flat surface. Replace the fan if any blade is more than 3/32 of an inch high.
• Fan clutch - Make three checks: One, look for "oily" streaks on the fan clutch housing. They are easy to spot because they attract dirt. The streaks usually indicate a silicone leak from the fan clutch. Replace the unit. Two, check the clutch bearing. Grasp fan blades opposite each other (three o'clock and nine o'clock positions, for instance) and try to move the fan and clutch assembly from side to side. Tip movement in excess of 1/4 of an inch indicates a worn clutch bearing. Replace the unit. Three, bring the engine up to operating temperature and turn it off. Spin the fan blade with one finger. If the fan rotates more than two turns, the fan clutch is freewheeling and the unit should be replaced.

The Water Pump
The water pump is often called the heart of the cooling system since it maintains coolant flow. Though today's water pumps routinely last tens of thousands of miles when supplied by a reputable manufacturer and properly installed as part of a well maintained cooling system, they are often victims of misdiagnoses and premature replacement.

For example, the presence of a small amount of coolant on the outside of the pump should raise little concern if that is the only symptom. A few drops of coolant on the pump is often part of normal operation, depending on the application and temperature, and does not indicate that the pump is "about to go."

Another falsely applied test is to check for play in the water pump bearing. Bearings require clearance to turn so some play is normal. Judging how much is too much is virtually impossible by feel alone. Predicting pump failure using these methods is more art than science, and is usually a waste of time.

When a water pump does need replacement, it is commonly because the seal has failed. The condition is often easily diagnosed since it is usually accompanied by a substantial loss of coolant that leaks out and pools beneath the engine.

Overheating
When cooling systems overheat, the problem usually stems from a lack of air flow through the radiator or coolant flow through the system. If the cause of the overheating condition is not obvious, first check for the faults that are the most accessible and simplest to remedy. For instance, be sure that ram air flow through the radiator is not being blocked by leaves or stray paper. Check the fan clutch condition as outlined previously. A quick way to determine if electric fans are in operating condition is to start the engine and turn on the air conditioner. This should cause the fan to switch on. If it does not, consider checking for an electrical problem with a switch or relay, or a possible PCM fault.

The system will usually overheat if coolant flow is blocked. Check flow from the radiator to determine if it is clogged. Also, a stuck-closed thermostat could be the culprit. Test it by starting the engine and letting it warm up for five to 10 minutes. Feel the upper radiator hose leading to the engine. You should feel a surge of warm coolant when the thermostat opens. Replace the thermostat if this does not happen. Another test would be to place a thermometer that reads up to 220 degrees Fahrenheit into the radiator filler neck and warm up the engine. When coolant begins to flow, read the temperature and compare it with the engine specs. If it is more than 10 degrees high or low, replace the thermostat.

Whenever a cooling system is drained, the vehicle manufacturer's recommended procedure must be followed when purging the air out and refilling the system. Air must be purged to avoid underfeeding. When air is trapped in the system, there is the risk of overheating, blown head gaskets and other severe engine damage.

It is also important to refill the system using a fresh, new coolant mixture. If the old coolant helped cause the original problem, putting it back in could spell double-jeopardy by allowing the fault to repeat.

Spring is in the air. This is the time to help ensure that summer is as enjoyable and uneventful for your customers as possible. Follow these simple procedures and perform cooling system checks now.

Craig Gottfried is a technical service representative for Airtex Automotive, the largest independent manufacturer of fuel pumps and water pumps

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