Manufacturers have addressed many cooling system problems, but regular maintenance is still important
Heat is one thing diesel engines produce in abundance. The role of the engine and truck design engineer is to take that heat and do something useful with as much of it as possible and get rid of the rest in the most efficient way.
The heat of combustion in diesels is roughly divided three ways. One third produces useful power. Another third goes out through the exhaust system, and the final portion needs to be taken out by the cooling system. Note the portion that goes out with the exhaust. Now remember when EGR was first introduced, and engineers started taking some of those heated exhaust gases and returning them to the engine.
Engineers, of course, understood what was happening, so it was no surprise that cooling systems would be stressed. As a result, cooling systems were beefed up, but in many cases, not enough. It was when the first EGR-equipped trucks went into service that we started hearing stories of melted plastic parts from never-before-seen underhood temperatures. Thankfully, such horror stories are, by and large, a thing of the past.
Truck manufacturers and fleet managers have done an excellent job keeping problems in check, but many of the remedies have increased costs and some are costing fuel mileage. Design engineers have found ways to better manage the airflow through the radiator and over the engine, but underhood temperatures are still high and components are still stressed. For example, when fan clutches were first introduced, they ran only 3% or 4% of the time. Now they’re running as much as 80% of the time. Fan clutches are certainly better now with higher quality steel in the shafts and better bearings, but emphasis must still be placed on system maintenance. It is the case that even a minor reduction in cooling system function can cause a diesel engine to self-destruct.
While designs have improved, cooling systems are still too often overlooked during routine PM inspections. Darry Stuart, president and CEO of DWS Fleet Management Service, says, “Industry-wide, maintenance is not being performed on cooling systems as it should be. For example, I find upwards of half of the radiator caps in service are defective. They need to be checked during PM inspections and replaced when necessary.”
Pressurize at every PM
Engineers from the National Automotive Radiator Service Association (NARSA) note that the mileage on a vehicle is not as big a factor in cooling system maintenance requirements as is the vehicle’s age. An aging vehicle has been exposed over time to environmental factors that can harm a cooling system ocean air, road salt, debris and other chemicals tend to deteriorate the system.
The best way to check a system for small leaks is to pressurize it before making an inspection. In many cases a small leak might not even be noticed because of ...