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In the early years of antifreeze/coolants (1920s & 30s) glycerin saw some usage, but because of higher cost and weaker freeze point depression, it was not competitive with ethylene glycol. Glycerin is a by-product of the manufacture of biodiesel (fatty acid methyl esters) made by reacting natural vegetable or animal fats with methanol. Biodiesel fuel is becoming increasingly important and is expected to gain a large market share in the next several years. Regular diesel fuels blended with 2%, 5%, and 20% biodiesel are now commercially available. The large amount of glycerin generated from high volume usage of biodiesel fuel has resulted in this chemical becoming cost competitive with the glycols currently used in engine coolants. For this reason, and lower toxicity comparable to that of propylene glycol, glycerin deserves to be reconsidered as a base for antifreeze/coolant.

Cavitation corrosion of cylinder liners in heavy duty engines can be one of the significant limits in engine operating time between overhauls. In both laboratory and engine dynamometer studies, engine coolants based on propylene glycol (PG) have performed better than similar formulations based on ethylene glycol with regard to cast iron cavitation corrosion. The performance of PG base coolant in all other aspects of coolant use was equivalent or superior to both industry standards and existing ethylene glycol (EG) products designed for use in heavy duty engines. Additionally, propylene glycol is cost competitive, readily available, and less toxic compared to ethylene glycol. A propylene glycol base engine coolant is described which assists the heavy duty user in solving many current problems related to cooling system servicing and engine life.

Cavitation, the study of formation, growth, and collapse of vapor cavities in the coolant jacket adjacent to diesel engine cylinder liners is an area of concern for diesel engine builders and users. Prior experimental work provides insight into parameters such as temperature and pressure. A commonly used bench test has been found not to correlate well with field testing. Also, field testing is very time consuming and costly. The 250 hour engine dynamometer coolant test in the industry costs over $60,000. Therefore, use of mathematical models for sorting out coolants is used, to study effects of coolant properties such as viscosity and surface tension on liner cavitation. Jet velocity at the time of implosion of the bubble is considered as a mechanism to quantify cavitation damage potential near a rigid wall. A model calculating jet velocity at the time of bubble collapse near a finite plate is determined using a commercial boundary element code, 2DynaFS.

This paper contrasts the differences between coolant maintenance practices for light duty engines and heavy duty (H.D.) engines. These differences explain why spent coolants from H.D. engines must be recycled using processes capable of removing dissolved contaminants, additives, and glycol degradation products, in addition to removing particulates. Examples and data are included that support this view. Finally, the requirements and recommendations of H.D. engine builders for recycled coolant to be used in their engines are reviewed and summarized.

Coolant filters have been used for over 30 years by heavy duty engine builders but little has been published in the technical literature documenting their performance. In heavy duty cooling systems a supplemental additive package is periodically added to the system (usually at the oil drain) to prevent the coolant from becoming corrosive and to stop the build-up of deposits which cut down on heat transfer. Not only is the coolant filter the most convenient and reliable method to deliver the supplemental additive to the cooling system, it removes debris from the coolant which can cause deposits and wear, aggrevate corrosion, and even plug heat exchangers. Additionally, the used coolant filter serves as a diagnostic trouble shooting tool. The results of extensive lab and field evaluations are reported documenting the benefits of coolant filtration.

In 1991, Frank Kelley of Caterpillar wrote: “In warm climates, it is still common for water with an appropriate concentration of supplemental coolant additive (SCA) to be used in heavy duty engine systems. This practice will probably become less acceptable as engine operating temperatures increase and aluminum components find their way into applications in heavy duty diesels in the future.” 1* That time has now come. Furthermore, as exhaust gas recirculation (EGR) becomes prevalent in 2002 engine designs, additional heat load will be transferred to the cooling system due to cooling the recirculated exhaust gas before its introduction to the air intake. This will further increase the need for the use of antifreeze/coolant due to the need for higher radiator top tank temperatures to handle the greater coolant heat load. Additionally, use of antifreeze coolants in older engines is very beneficial even though coolant temperatures may not be high.