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Coolant containing the proper amount of glycol and additives is critical to the reliability and durability of heavy duty diesel engines. Occasional coolant analysis is required in the field to insure that the proper coolant composition is maintained, otherwise severe engine damage can occur. There are several types of coolant test kits currently available in the field as well as commercial coolant analysis services. Some of the test methods used provide information that does not predict or correlate with a coolant's capability to prevent system corrosion and deposit formation. This paper examines the more widely available field coolant analysis methods and documents their strengths and weaknesses. Further, recommendations are made as to acceptable laboratory methods for the analysis of engine coolants.

A test method that will age coolants in a manner representative of coolant aging in the field is vital to the development of coolants that meet expected performance criteria. In an attempt to develop such a test, two approaches were taken. A phosphate buffered, molybdate/nitrite containing, propylene glycol based, heavy-duty coolant was aged in the laboratory using both a flow stand and a reflux apparatus. Samples of the coolant were taken at various time intervals during both tests. The samples were analyzed to determine glycol degradation product, sulfate and corrosion product accumulation, additive depletion, and pH changes. The results were compared to actual field results for the same coolant to determine which of the two approaches best simulated coolant degradation in the field. The flow stand appeared to best simulate actual field results.