Coolants are the least understood fluid in a heavy duty truck engine today. But a little attention to them can avert serious problems for your fleet. Photos: Prestone

Coolants are the least understood fluid in a heavy duty truck engine today. But a little attention to them can avert serious problems for your fleet. Photos: Prestone

If you’re a maintenance manager or owner-operator who is thoroughly confused as to what type of engine coolant should be in your heavy-duty diesel truck (much less what type of coolant is actually in the system) don’t feel bad. You’re far from alone. Heavy-duty engine coolant suppliers realize they have a problem on their hands today with multiple-colored coolants on the market — a situation further exacerbated by two different red-colored coolants with very different performance properties.

As is often the case, the confusion today arose from sincerely good intentions, says Dr. Frank Cook, chief technology officer at Old World Industries, which manufactures the Peak brand of engine coolants. Up until the 1990s, there wasn’t really an application-specific heavy duty diesel coolant on the market. Most fleets simply poured green-colored automotive-grade coolants into their trucks and then added supplemental coolant additives (SCAs) to insure increased wet sleeve liner protection.

This all changed, Cook says, when Old World decided to simplify things for its customers and began to offer its then-new FleetCharge heavy duty coolant with SCAs already formulated in the mixture. “At the time, SCAs were red in color,” Cook recalls. “And when you mixed them with fresh, green, automotive coolant, you ended up with a brown-colored fluid. So to differentiate our product, and help customers out, we decided to make FleetCharge coolants a fuchsia pink color. And that’s really where all these different colors we have today began.”

Two reds make it wrong

Before long, different-colored coolants began to appear. Including a yellow, extended-life coolant, and a new, red-colored coolant developed by Shell. “In the late ‘90s, we were working with Caterpillar, and they were concerned about liner life in their engines,” says Stede Granger, OEM technical manager for Shell Lubricants. “As a solution, they wanted to add nitrites to coolants, which boosted cylinder liner protection. And we decided to make that new Rotella coolant a red color in order to differentiate it in the market.”

Initially, Granger says, the new, nitrite coolants worked well, and most OEMs eventually started requiring their use as a warranty condition on new engines. “But engines back then weren’t built with much aluminum in them,” Granger says. “That’s not the case, now. Diesel engines have far more aluminum components to save weight and boost fuel economy. And now, after years of experience with these engines, we understand that in certain conditions, there can be a catastrophic chemical reaction between nitrites and aluminum in a diesel engine. This damage doesn’t happen all the time. But it is bad when it does.”

Colin Dilley, vice president, technology, Prestone, says that initially, nitrated organic acids helped prevent cavitation — a common physical reaction in a closed coolant system where miniature, imploding bubbles of air literally rip pieces of metal off of wet sleeve cylinder wall linings.

Problems begin, Dilley says, when nitrites under pressure react with the flux used in controlled atmospheric braising components in aluminum heat exchangers and radiators in the cooling system. “This process causes the formation of ammonia, and the coolant to become unstable and more basic, or less acidic,” Dilley says. “And, as a result, the protective additives in the coolant are depleted. So you end up with a fluid that is now causing corrosion inside the engine while offering severely reduced protection.”

The main culprit in this process is the liquid ammonia, Granger confirms. “You mix nitrites and aluminum and liquid ammonia forms,” he says. “This raises the Ph levels in the engine, which leaves aluminum surfaces open to corrosion — and can actually penetrate the surface of the metal in some cases. Worse, it affects other engine components as well — all the way down to engine seals.”

Once the problem was identified, Granger says Shell moved quickly to offer a solution. “We responded with a nitrite-free coolant blend before the 2010 engines launched,” he says. “And, initially, we dyed it yellow to differentiate it.”

But very quickly, Granger says, another problem emerged. “It was very hard to see that yellow coolant in a surge tank,” he says. “And we decided that red was a color that really worked well in that regard. So we decided to stay with it.”

And therein lies the problem: Some OEMs today recommend coolants with nitrite, while others recommend nitrite-free blends. And both solutions are dyed red. And, Granger cautions, mixing coolants degrades all of them, since they work in very different ways, chemically speaking, to protect an engine. “Once you mix coolants,” he says, “you quickly end up with a situation where you don’t have enough of the proper additives in any formulation to protect against corrosion.”

Suppliers offer test strips to identify which coolants or coolant mixes are in an engine’s cooling system. Using the strips may be the only way to know exactly what’s in there.

Suppliers offer test strips to identify which coolants or coolant mixes are in an engine’s cooling system. Using the strips may be the only way to know exactly what’s in there.

Simplified solutions on the horizon

“Most fleet managers today do not know exactly what is in their engine cooling systems,” Dilley says. “This starts with confusion over colors, and is amplified by topping off coolants when the truck is away from its home shop. You never know what is being poured in the radiator in those situations. As part of our research on this problem, Prestone has tested thousands of trucks, and there is almost always a mix of coolants in the radiator. So the problem is widespread.”

Dilley says coolant suppliers, including Prestone, responded to this problem with a host of new products, including new test strips to confirm and correct coolant blends, and new coolants that will simplfy that process. We are trying to remove as much confusion around these coolants as we can while not creating any additional issues,” he says. “Prestone simple, clearly marked test strips allow fleet managers to understand fully what type of coolant they have as well as any problems with the mixture. These products dovetail with Prestone customer outreach programs, including simplified coolant correction procedures and technical service bulletins to further educate fleets and help fix any coolant problems before they become catastrophic.”

“The good news is that it takes just a little bit of attention to correct the problem,” Cook says. “And no matter what a system has been topped off with in the field, you don’t always have to drain a system in order to correct the formulation of your coolant.”

To start with, Cook says, simply understand from the get-go your OEM’s recommendation for the correct coolant type and follow it. “The problem, of course, is for mixed fleets. In that case, or in the case where your coolant program has been lax, you’ll need to make the use of very simple test strips to check for nitrite in the coolant part of your routine maintenance procedures.”

In addition to its own line of simplified test strips, Granger says Shell will have a new, corrective, coolant additive on the market later this year that will remove a great deal of the guesswork surrounding red-colored coolant mixes today. “Our Rotella ELC Correction Fluid will include simple test strips that deliver a simple, ‘Go — No-Go’ reading on coolant additives and instructions for how much of the new fluid to add to correct accordingly,” he says.

Old World’s Final Charge coolant has a proprietary blend of organic acids that protect cooling systems without the need for nitrites, according to Cook. “The reality today is that some OEMs want nitrite in their coolants, while others do not. But Final Charge is a way to ensure protection across your entire fleet — even if it is a mixed-model truck fleet. And Final Charge can also be used to top off coolant with nitrites.”

Cook says that in many cases, a phobia he calls “chem-intimidation” is the problem, since many fleet managers suddenly feel like they’re back in high school chemistry class when coolant characteristics are being discussed. “Coolants are a lot like oil,” he says. “And it requires some level of attention in order to get them right. But even if you are completely confused as to what to do, you can always pull coolant samples and send them to your coolant provider. At Old World, we do forensic evaluations of coolant every day and provide our customers with clear instructions on how to proceed once a problem is identified.”

Jack Roberts

Jack Roberts

Senior Contributing Editor

As HDT's Senior Contributing Editor Jack Roberts has become known for his reporting on advanced technology, such as intelligent drivetrains and autonomous vehicles. A commercial driver’s license holder, he also does test drives of new equipment and covers topics such as maintenance, fuel economy, vocational and medium-duty trucks and tires.