There are many cooling system problems and failures. Some due to defective equipment but most of these problems have occurred due to incorrect information and maintenance practices. The chart shown below is a listing of most common problems in today's cooling systems. Along with each problem is a description of how it occurs, how it affects your engine and, most importantly, how to prevent it. Note that rust can occur even in a chemically balanced cooling system. If you observe rust, check the oil cooler or other parts of the oiling system that can infiltrate the cooling system.

Do it Right the First Time
Before you change your coolant you should thoroughly check the system. Start with a pressure test following manufacturers specifications for maximum pressure. Don’t over do it, a pound or two is acceptable. More pressure could damage the radiator core and welds, etc. Pressurizing the system will help to evaluate the system for leaks and hose condition. If you are not sure how to check hoses, go back to our archives at www.directbus.com If you have determined from the chart to replace the coolant be sure you flush the system thoroughly with a good brand cooling system flush. Make sure to flush with clean water to remove the flush chemical from the system. Some flush may not be compatible with the coolant. You would have removed the thermostat prior to flushing so now is a good time to replace the thermostat. Don’t forget to pressure check the radiator cap. Refilling the System
Refilling the system requires water. All water is not suitable for cooling systems, as some could have been softened by a chloride process or salt. Also high mineral content water cannot be made fit for the system. (Check with our engine manufacturer for their specifications on ppm of the following: Hardness, Chlorides, Sulfates and Dissolved Solids. However, even when refilling a system with the proper ratio of coolant and water, usually 50/50, you will still need to charge the system with the proper SCA (Supplement Coolant Additive). The supplement contains various inhibitors to fight the conditions in the above chart. How much SCA?
Standard rule is 4 ounces of liquid supplement to 1 gallon of coolant. Be sure to check the cooling system capacity to determine the ratio. What about Service?
SCA is depleted during protection of the cooling system metal components so the SCA must be replenished. This can be accomplished two ways. Service intervals to check and replenish with liquid SCA or Use a filter which contains SCA The latter is what is mostly suggested, as the filter will release the additive as the engine is running and cooling system is circulating. In any case the SCA should be check periodically to ensure protection.