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Coolant: classic, modern, and water-free

by Daniel Stern (part 4 of a series)

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One may easily ask why we need to use something other than water for coolant. One reason is given by the common name given to modern coolants: "antifreeze." Some agent has to be put into the water to prevent it from freezing in the cold, and destroying the engine (because water expands when it freezes). Over time, other factors became important even in areas where the temperature is always warm, including resistance to boiling (because engine temperatures are often over 212°), and rust and aluminum corrosion protection.

It used to be easy to pick coolant, because there was only one kind: the green ethylene glycol-based mix with silicate- and phosphate-based corrosion inhibitors, usually mixed 50/50 with water (and sometimes sold pre-mixed for nearly the same price). Then, through the 1990s and 2000s, many different coolants appeared under hoods and on store shelves.


The first departure was GM's Dex-Cool, a red-orange supposedly long-life coolant using organic acids instead of silicates and phosphates for corrosion inhibition. This stuff didn't work as advertised in the GM vehicles it came in; there were lawsuits, which GM lost, and it is known as "death cool" by those of us who have seen what it does to systems not even nominally designed for it.

One of the organic-acid corrosion inhibitors in Dex-Cool also acts as a plasticizer, which softens or dissolves rubber and plastic and attacks gasket materials not designed to resist it. Dex-Cool also does not prevent corrosion in systems containing particular combinations of metals, and it fails to prevent solder from corroding. Dex-Cool is definitely not a wise choice for any cooling system not specifically designed for it.


The proliferation of different coolant chemistries continued. The next big industry-wide consensus came in the late 1990s, with "G-05." This formula based on hybrid organic acid chemistry, and used organic acid corrosion inhibitors that do not attack plastic, rubber, or gaskets; it also uses some phosphate-type corrosion inhibitors.

Dyed bright orange, this was factory-fill in Chrysler products starting around 2000, and is now widespread throughout the auto industry. At least in North America, the industry seems to have standardized on dying it yellow. It is easy to get and affordable; even in older cars designed for the green stuff, my long experience with many years and many cars is that G-05 seems to give better corrosion protection over a longer period of time-and without damage to gaskets, seals, hoses, or other system components. So G-05 is definitely a sound choice for any Mopar cooling system (editor's note: proceed at your own risk when using non-specified coolant.)

Editor's note: This fluid can look pink in the Chrysler factory fill. The Mopar part number for a pre-mixed gallon (around $22) is 68163849AB, while Prestone sells a similar jug for $17. FCA specifies on newer cars that coolant must conform to the "MS-12106" specification, which is printed on the reservoir; not all manufacturers have printed it on the bottles yet.

Waterless coolant

Product Fluid Lubricant Automotive cleaning Liquid
There is an even better option, which costs more but brings big benefits: Evans waterless coolant. That is what it sounds like: a coolant containing no water at all, really clever stuff based on propylene glycol. Jay Leno uses it in his fleet of sky-high-dollar vehicles. I have done a good bit of research and experimentation with it, and I now run it in all my cars.

Corrosion is not a problem, because there is no water; corrosion is an electrochemical process and this coolant does not conduct electricity. Because there is no corrosion possible, there is no sacrificial corrosion-inhibiting chemistry required, so this coolant does not grow dirty or chemically exhausted and so does not require periodic replacement. The cooling system and the coolant remain spotlessly clean (editor's inevitable legal note: proceed at your own risk when using non-specified coolant.)

The waterless coolant operates at atmospheric pressure, thanks to its high boiling point. There is no water in it to generate steam, and its expansion with heat is slight, so almost no pressure develops in the system (steam, not the water pump, is what pressurizes a cooling system). Low-pressure operation causes almost no stress on radiator seams, water pump seals, gasket junctions, hoses, heater core, etc., (go back to the radiator cap discussion) so coolant leaks are much less likely.

Even with a leak, there is a much greater safety margin, a leak without pressure goes drip…drip…drip rather than FSSSHHHHHSHSHSHSHHHHH. In a catastrophic emergency you just top up with water and get where you're going. This doesn't ruin the Evans coolant, you just collect it in a clean catch bin and heat it to just over 212°F 'til the water's done boiling off, then pour it back into the system. At the time of writing, this coolant ran around $42 per gallon, including shipping; a prep flush product added around $34 per gallon.

Evans says this coolant suppresses ping (preignition, detonation, spark knock) by controlling localized boiling in the cylinder heads, on the coolant side of the combustion chambers. The idea is that once boiling occurs, no further heat transfer is possible at the boiling location because of the vapor layer between the metal and the liquid; the metal continues to heat up and so you get ping, which heats up the metal even more, and it becomes a vicious cycle. There's detailed discussion on the Evans site. If you can keep the metal surfaces wetted with coolant rather than blanketed with vapor, the metal temperature can be controlled and ping can be avoided.

The idea passed my common-sense test, so I did a practical test in my 1989 Dodge Ram pickup. With ordinary coolant, I ran a factory-spec 195° thermostat and, with the EGR disabled for diagnostics, I had to be very conservative with ignition timing or ping was significant and uncontrollable. With the waterless coolant, I went to a 205° thermostat, and even with no EGR I could no longer seem to make the engine ping. I gave it 2° more spark advance and still no ping, running on regular gasoline. I am sold on this stuff and now use it in all my cars; it really does every part of a coolant's job better-these are genuine and large improvements with no drawbacks except higher initial cost of the coolant, but that gets paid back (and then some) over time.

3: Radiators, old and new <> 5: Fans

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