Nothing shuts down a vehicle faster than an overheat condition. Failing to get to a worksite on time can cause problems, but none as great as having a truck out of service for days, to rebuild warped cylinder heads or scored cylinder walls in an engine costing up to $30,000.
Engines are cooled three ways. Running at highway speeds with air passing around the block provides some cooling, but most comes from coolant and oil. With oil, heat is absorbed by engine oil and carried to the sump and the oil cooler. That process doesn’t vary, unless you run out of oil.
Coolant is under your control.
Fully formulated coolant is a 50/50 mixture of ethylene glycol and water with either supplemental coolant additives (SACs) or long-life organic acid technology (OAT) additives. To keep the coolant operating properly and to protect engine parts, the additives must be checked and maintained periodically.
Glycol-based waterless coolant has recently gained popularity as a maintenance-free alternative to traditional coolants containing additives. So far, Evans Cooling Systems Inc. is the sole supplier.
Brought to market about a decade ago, the waterless coolant provides adequate lubrication for water pumps. Because no water is in the coolant, there’s no need to use additives to protect engines from water’s deleterious effects.
Traditional vs. waterless coolant
Water is an excellent heat-transfer medium when liquid, but it changes state. When it boils at 212° F, it creates vapor pockets that can insulate and hold heat in the metal rather than transferring heat away. When below 32° F, water freezes, expanding to generate enough pressure to crack engine blocks.
Freezing/boiling levels. Traditional, fully formulated coolants prevent freezing to -34° F. It also raises the boiling point to 224°. Since engines operate at close to water’s boiling point, the glycol adds a safety margin to prevent boil-over. Additional margin is provided by pressurizing the closed cooling system to 1 atmosphere (15 psi) above ambient. With the pressure cap, water boils at 250° and 50/50 coolant boils at 263°.
Waterless coolant, however, won’t freeze below 40° F and boils at above 375° — even without pressurization — giving a huge safety margin. Water carries scale-forming minerals, so waterless coolant prevents scale buildup. It doesn’t need a 15-psi radiator cap — the manufacturer recommends 1 to 2 psi, just enough to close the system. With no water to boil off, localized hot spots and mineral deposits are avoided.
Engine protection. Pitting is caused when water vapor bubbles form next to cylinder liners as they flex from the side thrust of pistons. When the bubbles implode, coolant impacts the outer walls of the liners with enough force to drill through. That lets coolant into cylinders and the oil sump.
In traditional coolants, supplemental additives form a protective coating that absorbs most of the impinging force. Without the protection, repeated implosions drill holes in the steel liners. Also, organic acids in long-life coolants protect from pitting. Protection levels must be monitored.
With waterless coolant, no water vaporizes and no bubbles form as the liners flex. Waterless coolant prevents voids. Since water is a corrosive agent, waterless coolant also resists corrosion.
Safety. The antifreeze in Evans’ nonaqueous coolant is mostly propylene glycol (PG), not ethylene glycol (EG) found in most conventional coolants. Unlike EG, PG is nontoxic. In fact, pure PG is used as a sweetener in many medications. If PG leaks and is ingested, no harm is done. But the green EG drops and puddles found in parking lots and driveways have proven poisonous to pets and small children attracted by the glycols’ sweet taste.
The drawbacks of waterless
Availability. You may be able to limp home on a slow leak, but if something catastrophic like a burst radiator happens, you can’t just repair it and replace with ordinary coolant. You need to find a service provider that carries Evans’ coolant. If you just add water, you lose all the benefits of your expensive changeover (see sidebar on page 21).
Expense. Evans coolant costs $40/gallon, as compared to $15 – $20/gallon for traditional coolant. With big bore diesels like snowplows having coolant capacity of 70 or 80 quarts (17.5 to 20 gallons), coolant alone can run $700 to $800/truck.
The justification is in fuel economy (when you adjust thermostat and settings, reducing fan operation frequency; see sidebar), the savings in maintenance supplies and labor, and the reduced wear and tear on the cooling system.
— Paul Abelson ([email protected]) is a former director of the Technology and Maintenance Council (TMC) of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.
How to change over to waterless coolant
Start by draining the current coolant. To make sure the system is thoroughly purged of water, disconnect hoses and let them drain completely. Open all drain valves. Allow time for all coolant to drain and evaporate. Do not flush the cooling system with water (less than 3% residual water is OK). If you need to flush, use Evans Prep Fluid. It is a system flush designed to seek out remaining water after draining the cooling system of an engine. Use it when block drains are unavailable or cannot be removed. A minimum of 2 gallons of Prep Fluid is recommended for heavy-duty diesel engines
After refilling, test for water using an optical refractometer. Its instruction sheet will indicate the proper scale to use.
Any engine will run well on waterless coolant as is, but to take full advantage you can make a few modifications. First, change the thermostat to one that opens at 215° F. Then have your engine dealer raise the fan-on temperature to 230°. In SAE Type II fuel-consumption tests (J1321) conducted by Auburn University’s PAVE Research Center, fuel-economy improvements exceeded 3%, primarily due to reduced fan-on time. Fans can draw 50 hp or more when on.