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Compatibility of coolant concentrate and SCA/water mixtures can be measured by their tendency to form insolubles during short term exposure to simulated operating conditions. A relatively simple, basic compatibility method was chosen to study the amount of silicate gel formed by coolant concentrate/SCA/water mixtures.. The method was modified to improve precision by first studying, then controlling key experimental factors. Further refinements were made to the method and a precision round robin was performed as part of the activity of the ASTM Committee D.15 on Engine Coolants.

Silica gel formation in heavy duty diesel cooling systems has increased with the increased usage of antifreeze with high levels of silicate. Gelation can occur when this type of antifreeze is mixed with supplemental coolant additives which are required to protect heavy duty diesel engine cooling systems, or when the undiluted antifreeze is stored for long periods. Gel in the cooling system can decrease coolant flow and heat transfer causing engine overheating. Gel formation is shown to be a chemical problem, not a problem of newer engine and cooling system design. Recommendations for avoiding the problem are included.

Early in 1987, members of the EMA (Engine Manufacturers Association) formed a Coolant Subcommittee to determine if there was a need for coolant product specifications and recommended coolant maintenance practices. There was quick, unanimous agreement that both were needed to enable the industry to improve cooling system durability and to reduce the incidence of cooling system problems related to engine coolants and their maintenance. Although there are a few commercial antifreezes for heavy duty engines that do not require an initial charge of SCA (Supplemental Coolant Additive), there is no industry-wide specification for such a product. One test needed as part of such a specification is a cavitation corrosion bench test that correlates well with engine tests. This paper documents some work being done to develop such a bench test. The bench test results for various coolants are compared to 200 hour engine dynometer test results for the same coolants.

Approximately 200 to 210 million gallons (or about 2 billion pounds) of antifreeze or engine coolant are produced in North America each year. About 80 percent of this is sold to refill leaking cooling systems. This paper compares the environmental impact of additives in leaking and improperly disposed coolant to other sources of these same chemicals.

Organic acid (OA) or organic acid technology (OAT) coolants are being aggressively marketed today as a far superior product to more conventional coolants. Claims are being made such as superior performance, as well as a product that is friendly to the environment. Further, some producers of OAT coolants claim that it is the only product in the market that can provide long life as well as extended service intervals. This paper is being written to closely examine and challenge these claims. High quality conventional coolants offer all the advantages claimed for OA coolants and in some cases provide superior performance.

Coolant filters have been used for nearly 50 years by heavy duty engine manufacturers but little has been published in the technical literature documenting their performance. In heavy duty cooling systems an extender is periodically added to the system to prevent the coolant from becoming corrosive and replenish additives that stop the build-up of deposits which reduce heat transfer. Not only is the coolant filter the most convenient and reliable method to deliver the extender to the cooling system, it also removes debris from the coolant which can cause deposits and wear, aggravate corrosion, and even plug heat exchangers. Additionally, the used coolant filter serves as a diagnostic trouble shooting tool. This paper concentrates on the value or importance of filtering debris from the coolant of heavy duty diesel engine cooling systems. Published literature is reviewed and recent data from lab testing is reported.

This paper reports results from an extensive literature search as well as a comprehensive laboratory and engine dynamometer evaluation as to the effects of coolant and moisture on lubricating oils and heavy duty diesel engines. The reactions of glycol from engine coolant when it contaminates the oil and the detection of coolant in the crankcase are dealt with at length, as well as the effect of coolant and moisture on bearings. Finally, a laboratory bench test to evaluate a heavy duty lubricant's moisture tolerance is proposed.