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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).

Increasingly challenging international engine emissions reductions have resulted in some advances in engine emissions technologies that may motivate a change from the customary ethylene glycol and/or propylene glycol bases that have been the mainstay of engine antifreeze formulations for almost a century. The new engines' components, especially exhaust gas recirculation (EGR) devices, generate much greater thermal stress on the engine coolant. The oxidation of ethylene glycol and propylene glycol may be accelerated dramatically, resulting in coolant unsuitable for continued use in as little as a few months. The industry has been working towards extended engine coolant service intervals1,2,3,4, with some recommendations for service extended to as long as five years. It follows, therefore, that a requirement for coolant change at four to six month intervals (due to accelerated oxidation & aging) would be unacceptable to vehicle owners.

The ASTM D 2809 test method, “Standard Test Method For Cavitation Corrosion and Erosion-Corrosion Characteristics of Aluminum Pumps With Engine Coolants” was first published in 19691. The method involves a copper-pipe circuit through which coolant solution, heated to 113°C, is pumped at 103 kPa for 100 hours. The method was modified to change the pump used in the test in 1989. It was updated in 1994 to accommodate a change in the cleaning procedure and was subsequently reapproved by the ASTM D-15 Committee on Engine Coolants in 1999.2 Tests recently conducted on several modern coolants have produced “failing” results, but the coolants are performing well in the field. Further, the repeatability and reproducibility of the method have been questioned. A round-robin series of tests sponsored by the Ford Motor Company revealed significant variations and cause for concern.

Reverse Osmosis (R/O) is reported by Huff' to offer a high volume engine coolant recycling process with very significant purification capabilities. The higher productivity per investment dollar, in spite of the initial capital cost of the equipment, may present the best opportunity for a practicable commercial recycling method capable of producing coolant that compares favorably with new (virgin) coolant. A system described by Huff has, since its introduction in 1990, been re-invented and re-engineered to optimize both the quality and cost effectiveness of the process. This paper describes many of the technical obstacles in the evolution that had to be overcome, and reports the state-of-the-art in commercial reverse osmosis coolant recycling technology. Process improvements that affected coolant quality and productivity are recorded.

In the late 1980s engine coolant recycling technologies were developed in response to a temporary but significant increase in the cost of ethylene glycol. Among these technologies was the adaptation of reverse osmosis water desalination processes by Stanadyne Automotive Corp.1 The technical paper describing the reverse osmosis (R/O) technology reports that the process efficiently recovers ethylene glycol and water in a sufficiently pure state to allow its use as a base fluid to reblend into engine coolant. Data generated in standard ASTM bench tests has demonstrated the capability of properly reinhibited R/O recycled engine coolant (ROREC) to comply with the performance requirements of accepted SAE, TMC, ASTM and OEM specifications. The technology has been applied commercially and this paper reports the operating experience of 15 users in Texas and California with diverse service applications. The experience has been very good.

This paper reports how, as part of a continuous quality improvement program, a major high output (over 1000 KW) engine OEM and its coolant technology supplier identified specific opportunities for improving the coolant chemistry used in the subject engines. Specific objectives included: optimize the stability of the coolant chemistry as evidenced by the reduction or elimination of radiator tube plugging; reduce the need for cooling system cleaning and maintenance; extend the life of the coolant to coincide with the time period between engine overhauls; Improve maintenance simplicity and tolerance for errant maintenance practices. The existing coolant program, derived from successful highway engine service practices, was reviewed and the chemistry of the supplemental coolant additive (SCA) was modified to more precisely address the characteristics of the subject engines. In particular, the SCA was reformulated without silicate, since the subject engines contained no aluminum.

This paper discusses observations of the apparent effects of choosing to operate Heavy Duty Diesel (HDD) Engines with no coolant change interval, maintaining the coolant with a delayed release Nitrite/Borate/Very Low Silicate SCA and using coolant that is of a similar, fully formulated, low silicate, low total dissolved solids technology. It should be carefully noted that this practice is currently neither accepted nor recommended by most diesel engine manufacturers. The authors have accumulated the data from actual fleet maintenance files, and believe that observations, data and correlations seemed significant enough to warrant dissemination, and, more importantly, they suggest that further study would be of extreme value to further prove that existing North American coolant technology may have useful life far exceeding current OEM recommended change intervals.

This paper discusses the observations, laboratory analysis, and approach implemented in addressing wax related, low temperature flow problems of low sulfur diesel (LSD) fuels that have been effective in field use. It should be carefully noted that this was not a controlled field test. The authors believe that the observations, data, and correlations are significant enough to warrant dissemination. They suggest that a controlled study would be of extreme value to further solving wax related diesel operations effected by low temperature conditions.