"Extended life" offers cost, environmental benefits.
Many fleets do not protect their cylinder liners from the damage that can result from combustion vibration. Cylinder liner cavitation and pitting are commonly caused by the vibration from combustion shock loads, which creates a low pressure area along liner walls. When this happens, air bubbles form in the coolant and implode on the surface of the liner, blasting away bits of metal.
Conventional coolants that rely heavily on the use of nitrites to form a protective film often require the addition of a supplemental coolant additive (SCA) at the initial fill and again at 12,000- to 20,000-mi. intervals to ensure protection. However, extended life coolants (ELCs) are now available that are capable of providing up to 600,000 miles of complete cooling system protection without periodic renewals of SCAs.
The availability of ELCs means that some heavy-duty diesel engines can now be operated to overhaul without coolant changes at no compromise of engine or cooling system reliability. This can save some serious money for fleets since standard coolant should be renewed periodically. The recommended change interval varies from one engine manufacturer to another, but as recently as last year was generally in the area of 200,000 miles or 4,000 operating hours for most North American manufacturers, according to a 1996 report from Penray.
A growing interest in reducing hazardous waste, expense, and the negative environmental effects of spent coolant has prompted many fleet operators to seek coolant management alternatives. One option is a coolant that can be operated until the engine needs to be overhauled, a period now approaching 1-million miles or 20,000 operating hours for the most advanced of today's heavy-duty diesels, according to Penray.
Last March, Caterpillar launched a 600,000-mile extended life coolant that requires the addition of just one "Cat Extender" to the system at 300,000 miles, eliminating problems of improper maintenance, additive dropout, gel formation, and radiator clogging.
According to Cat, its ELC provides significant cost savings compared to traditional coolant and additives. One Cat ELC with one Cat Extender at 300,000 miles is said to cost $77.39 over 600,000 miles, compared with $211.05 for an engine using traditional coolants with the recommended SCAs added every 15,000 miles.
Texaco's ELC was introduced in 1995 and has since been road-tested to 600,000 miles, twice Texaco's original 300,000-mile specification for the product. The Texaco ELC system relies on a coolant inhibitor film formed by carboxylates, which deplete at a very slow rate. This technology provides superior long-term protection against wet sleeve liner pitting, outstanding protection against aluminum corrosion, and improved heat transfer, according to Texaco.
Unlike traditional coolant-antifreeze, the Texaco ELC system does not contain silicates, nitrates, borates, phosphates, or amines. If coolant chemistry goes awry, those additives can lead to the formation of silicate gel, or "green goo," and hard-water scale in the cooling system. They can also form abrasive dissolved solids, which are a major cause of water-pump seal failures.
The only addition necessary to continue the life of Texaco's ELC is one dose of extender at 300,000 miles of on-road use, and at three years or 6,000 hours of off-road use.
Texaco's carboxylate technology has been tested in more than 150 heavy-duty vehicles with varying engine designs, including the Cummins 315 and N14 series; the Caterpillar 3000, 3100, and 3400 series; and Detroit Diesel 149, 60, and 6V92 series. It has met all requirements of ASTM specifications for heavy-duty and light-duty antifreeze-coolant, including ASTM D4985, D3306, D5345, and D4656.
These extended life products have been made possible through the development of advanced inhibitor chemistry techniques that are enabling antifreeze-coolant manufacturers to prepared so-called "fully formulated" ELCs. Fully formulated antifreeze contains all the necessary inhibitors to protect a diesel engine, and does not initially require an SCA.
Penray's inhibitor chemistry is used to produce a number of fully formulated products by manufacturers like Old World Industries, whose biggest seller is Fleet Charge, a silicated, fully formulated coolant/antifreeze. It also makes Final Charge, an extended life non-nitrided, heavy-duty antifreeze that needs an extender added at 200,000 miles.
Penray's Need-Release extended service interval (ESI) coolant filter provides 100,000 miles or one year of service if used with a traditional phosphate, low-silicate (ASTM D4985 specification) antifreeze. It also manufactures the Pencool liquids that act as inhibitors.
The Need-Release system cannot serve as the only inhibitor in a coolant, but must be used with an antifreeze. The combination of the Need-Release system with the proper coolants is the essence of Penray's Fill-For-Life program.
Fleetguard Inc. produces the ES system, a non-organic acid system that uses the ES filter in conjunction with the coolant to guard against liner cavitation.