Wet-Sleeve Engine "OAT Coolants" Nitrate free
Although cavitation can be devastating, it's also easy to prevent, simply by maintaining a film of cavitation-resistant native oxides on the sleeve's outer wall. The diesel engine's coolant is responsible for keeping this protective film in good repair, but to do so, it must in turn be adequately maintained. This means, essentially, keeping the coolant's additives in proper concentration.
For many coolants, a "supplemental coolant additive" (SCA) package not only has compounds that help the cooling system resist corrosion, scaling and attack by acids, but also contains nitrite, which mends the sleeve's protective-oxide film when cavitation tries to wear it away. Some SCA packages also contain molybdate, intended to enhance nitrite's healing action and thus allow lower levels of nitrite, which, in excessive concentrations, may contribute to solder corrosion.
If you still use "conventional coolant," a heavy-duty, low-silicate antifreeze with an ASTM D4985 specification, then remember that this antifreeze contains no supplemental coolant additives. At initial fill, along with mixing it with 50 percent water, you must add an SCA package, typically at a ratio of one pint to four gallons of coolant.
A better alternative, says Eaton, is to use "fully formulated" antifreeze that meets ASTM D6210 specifications. These antifreezes already contain SCA components and thus require no initial treatment. In fact, all makers of vehicles with heavy-duty diesels now require coolant meeting this standard.
If your diesel's cooling system is filled with an "extended-life coolant" (ELC), then it contains an antifreeze formulation of ethylene glycol and special organic (carboxylate) acid additives, which replace the compounds in a typical SCA package. All heavy-duty-diesel manufacturers at the present time, however, says Eaton, require that ELC formulations also contain nitrite or the nitrite-molybdate combination.
Yet another coolant family uses "hybrid technology" and contains benzoate and inorganic inhibitors, which offer extended service and improved compatibility. Hybrids intended for use in heavy-duty diesels also contain nitrite and are maintained similarly to other coolants meeting the ASTM D6210 specification.