Of course, your OEM maintenance recommendations are your primary source for how to structure your coolant system PM program. But you can also refer to this handy guide provided by Stede Granger, OEM technical services manager for Shell Lubricants.
❶ Determine Coolant Type: The type of coolant in use in the vehicle may be determined by several methods including decal or sticker information on the vehicle, customer and/or truck service records and OEM recommendations.
❷ Visual Inspection: Obtain a representative coolant sample and visually inspect the coolant for clarity and color. The coolant should be bright and clear, free of dirt, debris, rust and other contaminants, and be representative of the color of the coolant recommended for the vehicle. If the coolant appearance, clarity or color is unsatisfactory, check for possible contamination with other coolants, fuel, oil, combustion leaks, etc.
❸ Test Freeze Point: A 50/50 mixture of ethylene glycol-based antifreeze concentrate and water providing a freeze protection of -34°F is recommended for most parts of the US, although 60/40 mixtures are sometimes used in colder regions. It is suggested that the freeze point be maintained between -30°F and -40°F for most U.S. regions regardless of coolant type and at no times should the freeze point be higher than -20°F or lower than -60°F. A refractometer is the most accurate and recommended method to determine the freeze protection. Refractometers today are very reasonably priced and are available from tool suppliers.
❹ Check Corrosion Inhibitor Level: ELC coolant corrosion inhibitor levels are generally maintained by maintaining the proper freeze protection and protecting against contamination with other coolants. Therefore, if the coolant appearance and freeze point are satisfactory, it is usually not necessary to test ELC coolants for corrosion inhibitor level. In cases where ELC coolants may have been topped off or contaminated with conventional coolants and/or where the color does not appear correct, ELC test strips, such as the Shell Rotella test strips, can accurately determine the OAT level in ELC coolants.
❺ Top Off Cooling System: Fill or top off the cooling system with the recommended coolant. Mixing of ELC coolants and conventional coolants or conventional coolants and ELC coolants is not recommended. The mixing of different coolant chemistries will dilute the intended corrosion inhibitor and reduce the level of corrosion protection. Therefore, mixing of different coolants should be limited to no more than 20%.
❻ Check Coolant Sticker: Assure the truck has a sticker identifying the type of coolant in use, service date and/or next service date.