Would you believe cooling system failures are the No. 1 cause of mechanical breakdowns on the highway? That's what statistics published by the U.S. Department of Transportation tell us. It's not surprising considering how badly most cooling systems are neglected these days.

In April, the Car Care Council offered motorists free vehicle inspections at more than 400 check lanes around the country. The inspections were done to raise public awareness of the council's "Be Car Care Aware" campaign during National Car Care Month. With respect to cooling systems, here's what they found:

20% (one out of five!) of the vehicles inspected had old coolant that needed to be flushed and changed.
16% (one out of six) had a low coolant level in the coolant reservoir, and 11% had a low coolant level in the radiator.
8% had visible coolant leaks.

The opportunity for cooling system maintenance and repairs are obviously there. But many motorists never check anything under the hood until a problem occurs. Then it's often too late and the damage has already been done.

An undetected coolant leak or low coolant level can lead to overheating. This can be very damaging, especially in engines with overhead cams and aluminum cylinder heads, because excessive heat causes the cylinder head to swell and distort. This may cause the camshaft to bend, jam or break, or it may crush the head gasket and cause the head gasket to fail....