Examinations of Extended Life Heavy Duty Engine Coolant Filters 2004-01-0057

Since 1996 engine coolants and/or coolant management programs that offer extended service have been heavily promoted. Coolant chemistry is often affected by both depletion and dilution of important protective additives. Two different strategies are prevalent in the marketplace. The first utilizes advanced fully formulated conventionally inhibited ethylene glycol coolants with a controlled-delivery coolant filter that both filters the fluid and provides replenishment of corrosion inhibition chemistry as the coolant ages to greatly extend the life of the coolant compared to earlier practices. The second alternative employs the use of ethylene glycol inhibited with fully formulated chemistry dependant on aliphatic or cyclic carboxylic acids that are sometimes combined with inorganic inhibitors (sometimes called organic acid or hybrid organic acid technologies). The success of this approach is dependant on these inhibitors depleting at such a slower rate, so that they need less maintenance, and in the coolant being maintained to prevent dilution of the coolant with water or alternatively inhibited coolants.

Because engine coolant filters are not necessary as additive delivery devices in coolants inhibited with carboxylates, some users have omitted (new production) or removed (existing units) coolant filters from vehicles operating on carboxylate coolants. This was done to reduce cost. However, earlier studies¹ found that the value of coolant filtration extends beyond their convenience as additive delivery devices. The authors pondered the potential negative effects on system reliability when the filters from heavy-duty diesel engines are removed. To date, it has not been suggested that removing diesel fuel, transmission fluid, or engine lubricant filters would be cost-effective. The authors question if coolant systems are fundamentally different?

This paper reports the findings of over seventy heavy-duty coolant filters that were gathered at random from the diesel engine community. Each filter was opened, carefully examined and the condition of the media and additive (if it contained additive) documented to develop data leading to the determination of the value of coolant filtration to heavy-duty engine coolant systems using any modern engine coolant. It was important to understand if the overall systems has changed since the last such investigation was published in 1988, or if the findings of that paper continue to be valid in today's modern cooling systems.