![]() ![]() Where nitrite based inhibitors in conventional coolant formulations provide protection by forming a layer that coats or covers the total metal surface, organic acid inhibitors protect from cavitation by chemically interacting with the metallic surface itself. Some organic acid formulations will include some levels of nitrites in their formulations also (NOATs). These abrasive scale particles can accelerate wear in cooling system components such as radiators, water pumps, and hoses.Įxtended life fluids (ELCs) use organic acid technology (OATs) to protect wet sleeve cylinders from cavitation. The displaced scale from these systems becomes an abrasive particle floating around in the coolant, which requires periodic flushing. In order to replace the metal surface void and the displaced scale that was removed upon implosions due to cavitation, a cooling system using conventional coolant formulation must have remaining unconverted SCA in liquid form available in the coolant. Nitrites tend to deplete rapidly in conventional coolants and must be replenished at regular intervals with SCAs (Supplemental Coolant Additives). ![]() This oxide film quickly restores surface material over the liner by drawing additional available nitrite in the coolant. Nitrite will form a thin sacrificial protective oxide film on the coolant side of the liner wall. Some formulations will use molybdate in combination with nitrite for enhanced protection against cavitation. When using conventional coolants in a wet sleeve diesel engine liner application nitrite is the primary inhibitor to protect against cavitation erosion, which results in liner pitting on the outside of the cylinder sleeve. Without inhibitor additives the process would quickly penetrate cylinder walls and cause detrimental harm to the engine lubricant and eventually the engine itself. These violent microscopic implosions at high pressures cause pitting and erode metal surfaces they are in contact with. This results in cavitation when these vapor bubbles collapse violently (imploding) when the coolant fluid rapidly goes from a low pressure phase to a high pressure phase. During low pressure phases vapor bubbles are created. This vibration causes expansion and contraction of the cylinder sleeve, which in turn creates high and low pressure zones in the fluid between the cylinder sleeve and engine block where the engine coolant flows. This is the first of several informational pieces on diesel engine coolant system reliability.Ĭavitation in the coolant fluid on the outside of wet sleeve liners is caused by vibration of the cylinder wall while the piston is in motion. It is estimated that a majority of diesel engine downtime is coolant related and coolant leaks through wet sleeve liners is a major cause of coolant contamination in the engine lubricant. The pre-diluted stuff is more convenient of course, but you end up paying a lot more for less coolant.Coolant system cavitation in wet sleeve engine liners is just one aspect of coolant system technology trouble shooting. Years ago coolant was always sold as pure coolant, and you'd have to dilute the fluid yourself with water. One thing to keep in mind with nearly every modern jug of coolant you’ll come across: They’re all pre-diluted. All GM cars use something called Dex-Cool from the factory. Plenty of others like BMW and Volkswagen do the same thing. Many times, the coolant is actually branded for the car you’re going to put it in.įor example, Honda sells its Type 2 Antifreeze/Coolant in all its dealers. They’ll sell the coolant for your specific make and model, and it’s guaranteed to be the correct one. The easiest way to make sure you’re getting the right coolant for the job is to go to your car’s dealership. Finally, HOAT is a derivation of OAT that requires the same time change interval unless otherwise specified. General Motors vehicles use this formula and normally require a change after five years or 50,000 miles. It needs to be changed every two years or 24,000 miles, making it far inferior to newer formulas. Play icon The triangle icon that indicates to play ![]()
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