By Paul Abelson, senior technical editor
Q. After we published our story about Robert Sliwa’s AirFlow Bullet Truck in the June issue, we received inquiries about the waterless antifreeze he uses.
What waterless coolant does Sliwa use? Will it lubricate water pumps as well as regular antifreeze? Have any fuel economy tests been run? Why is it different from regular antifreeze? What are the benefits? What are the problems or downside to using it? Can I just pour it in as a replacement for my regular coolant or does it need special preparation?
A. These excellent questions made me go back to school on cooling systems and coolants.
The supplier is Evans Cooling Systems Inc. Evans is the pioneer in waterless coolant and has at least one partnership overseas in the works. Conventional coolant includes 50/50 ethylene glycol and water with either traditional supplemental coolant additives or long-life coolants with organic acid technology.
Evans waterless coolant provides adequate lubrication for water pumps. Because no water is in the coolant, there is no need to protect engines from water’s effects by using additives.
Water is an excellent heat transfer medium when it is liquid, but is susceptible to boiling and freezing.
At 212 degrees, it creates a vapor that can insulate and hold heat in the metal rather than transferring heat away. Below 32 degrees, water expands as it freezes. That can generate enough pressure to crack cast iron engine blocks.
A 50/50 blend of traditional ethylene glycol antifreeze and water will prevent freezing down to 34 degrees below zero. It also raises the boiling point of water to 224 degrees.
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 with a 15 psi cap. With it, water boils at 250 degrees and 50/50 coolant boils at 263 degrees.
Without pressurization, Evans coolant freezes at 40 degrees below zero and boils at 375 degrees, well above any engine’s operating temperature. Since water carries minerals into the cooling system, waterless coolant prevents scale buildup. Rather than a 15 psi radiator cap, Evans recommends 1 to 2 psi, enough to close the system.
With no water to boil off, localized hot spots are avoided inside the engine. Liner pitting is caused when bubbles form next to cylinder liners as they flex from side thrust of pistons. When the bubbles burst, liquid impacts the outer walls of the liners forcefully.
Supplemental coolant additives form a coating that protects liners from most of the impact. Without the protection, the bubble bursts actually drill holes in the steel liners. The organic acids in long-life coolants also protect against pitting.
With waterless coolant, water bubbles do not form. The pure glycol coolant quickly fills any voids created when the bubbles pop. Because water is the corrosive agent in coolant, waterless coolant resists corrosion.
The antifreeze in Evans coolant is propylene glycol, not ethylene glycol found in most conventional coolants.
Propylene glycol is nontoxic. In fact, pure propylene glycol is used as a sweetener in many medications. Green ethylene glycol drops and puddles have been poisonous to pets and small children attracted by the glycol’s sweet taste.
Evans coolant can be a direct replacement for traditional or long life ethylene glycol coolants.
To change over, drain the current coolant. Thoroughly purge the system of water by disconnecting hoses and letting them drain completely. Evans has a conversion fluid to assist with this.
Open all drain valves. Allow time for all water to drain and evaporate. Do not flush the cooling system. That will just add water back. A little residual water is OK, but should not exceed 3 percent by volume. You can test after filling, using an optical refractometer. Check the instrument’s instruction sheet for the proper scale to use.
To take full advantage of the engine running well on waterless coolant, you can make a few modifications. First, change the thermostat from your current 180 or 190 degrees to 215 degrees. Then have your engine dealer raise the fan-on temperature to 230 degrees. You can also add a ResistorPac from Evans in series with the temperature sensor. It will raise the fan-on temperature and elevate the de-rating overheat protection temperature. Check with Evans or your dealer for the correct ohm rating for your engine.
If ordering a new truck, specify Evans waterless coolant, a 215 degree thermostat, and ECM programming set to provide fan-on at 230 degrees, fan-off at 217 degrees, de-rating at 235 degrees and auto-shutdown at 240 degrees.
In SAE Type II fuel consumption tests (J1321) conducted by Auburn University’s PAVE Research Center, fuel economy improvements exceeded 3 percent, primarily because of reduced fan-on time.
As for the downside to switching, cost is a major factor. Evans coolant costs approximately $40 per gallon. With over-the-road diesels having coolant capacity up to 17.5 to 20 gallons, the coolant alone can run $700 to $800.
Another factor is availability. If you have a slow leak, you may be able to limp home on the gallon or two you carry with you, but if something catastrophic like a burst radiator or heater hose happens, you can’t just repair and replace with ordinary coolant. You need to find a service provider that carries Evans’ coolant. If you add water, you lose all the benefits of your expensive changeover. LL