By John Smith
Stede Granger probably fields more questions about heavy-duty coolants than most people. As an OEM technical service manager for Shell, he is one of the guys with answers concerning the properties of everything from supplemental coolant additives (SCAs) to extended life coolants (ELCs).
But even Granger can be surprised by the extent of the misconceptions that exist.
That point was brought home when he visited an off-road fleet where workers were using water to top off coolant reservoirs during the summer months. Not the recommended 50/50 mixture of coolant and de-ionized water. Not even a mixture of the chemical compounds and the scale-forming water from a well. Just plain, old-fashioned H2O.
“Some technicians don’t understand how important it is to maintain freeze protection,” he admits.This may be an extreme example, but sales figures demonstrate that some North American equipment owners may not understand all of the features and benefits that exist with different coolant formulas.
“Green [automotive] coolants haven’t disappeared yet and we’re two iterations down the road with ELCs,” observes Carmen Ulabarro, direct channel manager, Chevron Products, referring to how the formulas have evolved. As a conservative estimate, she suggests that between 15 to 20 percent of the traditional green fluids are still finding their way into the reservoirs of heavy-duty trucks.
“The big dog fleets, they’re fully formulated,” she says, “but that owner-operator guy who has four to five trucks, he’s probably still going on green.”It begs a question: Do customers understand the difference between a green silicate-based automotive coolant, the “fully formulated” products specifically designed for heavy-duty trucks, and the ELCs that last hundreds of thousands of miles? Or are they making the same purchasing decisions out of habit?
Unlike conventional silicate-based automotive formulas, a fully formulated truck coolant comes with the initial dose of SCAs – including the nitrites or nitrite-molybdates that are used to combat the pitting of cylinder liners. These chemical compounds stop that
problem “dead in its tracks,” Granger says, referring to cavitation, the damage that can otherwise be caused by bubbles that form and collapse within the coolant.
Engines that generate higher horsepowers or higher heats are the most likely to face this challenge, says Dave Turcotte, technical director for Valvoline. “In the case of [exhaust gas recirculation], anything that increases the thermal load of the engine is going to increase or aggravate corrosion issues.”
He splits the North American fleet into thirds. About one-third of diesel engines do not face cavitation corrosion at all. Nitrites will completely eliminate the problem in another third of the engines, while the chemicals will merely slow down the process in the equipment that remains. “There’s still the good, the bad and the ugly,” he says. And when it gets ugly, it also gets really ugly. The related pitting could bore a hole into a cylinder liner in as little as 30,000 miles.
Meanwhile, the requirement for frequent flush and fills was addressed through the introduction of ELC formulas that were first introduced by Caterpillar in 1996, shortly after General Motors developed its Dexcool mixtures for automotive applications. An ELC does not contain the abrasive silicates that can wear out water pumps or plate out on heat transfer surfaces. Its organic acid technology also helps to maintain the levels of nitrites or nitrite-molybdates – extending the life of the coolant – while the core chemistry adds another level of protection against liner pitting.
“It [the use of ELC] is all about reduced maintenance, excellent performance and simplification of the maintenance system,” says Ulabarro. At the very least, the mixture added to the cooling system of a heavy-duty diesel engine should meet the related ASTM standard known as 6210, compared to the mixtures added to automotive applications that need to meet 3306. In addition to that, the Technology & Maintenance Council has Recommended Practice 329 to define standards for the fully formulated offerings that include nitrite and nitrite-molybdates.
But be wary of a label that promises to “meet the performance requirements” of 6210 because that could mean the formula does not meet the related chemical standards. The label should suggest the fluid “meets or exceeds” such requirements, Ulabarro says. “The best you can do is ask, ‘Does it say 6210 and am I buying it from a reliable supplier?’”
Users also should ensure that the coolant meets the needs of a specific engine. “There are some small differences from time to time,” Granger explains. That will make it important for a shop to look for references to standards such as Cummins 14603 or DD 93K217 to meet their specific needs. The Cummins 14603 test places a particular emphasis on the protection of solder, Turcotte offers as an example.
TRADEOFFS IN TECHNOLOGIES
The challenge, however, is that it is impossible to meet every single need. “When you pick technology, there are tradeoffs,” he says. “The most important thing is for people to read and understand what the engine manufacturer is saying in their guidelines. There is information online and in written form. A few minutes of review will give them insight … I hate to say this, but read the manual.”
Every coolant needs to protect metals, effectively transfer heat and protect against freezing. But engine manufacturers can look beyond that to address issues such as flow-related erosion or the need to protect aluminum, which can be under attack in a high-heat environment.
The makers of Detroit Diesel and MBE engines had until recently balked at the presence of nitrites or nitrite-molybdates in ELC formulas (excessive levels have been known to attack aluminum cooling system components). That has since been addressed with a recent service bulletin that permits the presence of these chemicals.
Ulabarro says the underlying resistance to the nitrites can be traced to Europe, where the compounds have been linked to cancer. “They put nitrites in their hot dogs, but they don’t put it into their coolants,” she says, repeating a mantra that comes up in many related conversations. But while nitrites need to combine with amines to create a carcinogen, these fluids no longer contain amines.
Turcotte suggests that the main concern about nitrites is linked to an environmental concern. “If you get into corrosion, particularly on aluminum … you could have a nitrite reduced to ammonia,” he says. “Europe uses a lot of aluminum in heat exchangers.” In contrast, U.S. equipment is more likely to incorporate copper and brass.
“The major North American domestics – Caterpillar, Cummins, DDC, Mack, Navistar – all allow for nitrited coolants,” Turcotte adds, noting how MAN and MBE engines can accommodate the formulas as well.
As important as various chemicals can be, there can also be too much of a good thing.
“You want just the right amount of additives to do the job,” Granger says. Excessive amounts of silicate, for example, will wear out water pumps. High levels of nitrites can lead to corrosion issues for aluminum parts.
These excess quantities can emerge if an over-zealous maintenance team spins on a filter full of SCAs every 5,000 miles, Ulabarro says, referring to how the following spikes in nitrite levels can have an impact on solder. “And if you over-treat with supplemental coolant additives, you can get silicate dropouts that can cause plugging issues.”
“If they’re using SCAs, they should follow the manufacturer’s guideline around maintenance, and that will typically include a filter that has a number of SCA units,” Turcotte agrees. If test strips are showing that nitrite levels are too high, that can be addressed by temporarily using a blank filter. “Different engines have different appetites,” he says.
Other shops that simply top off reservoirs with undiluted coolant eventually can sacrifice heat transfer abilities. Even the quality of the water can play a role in the effectiveness of the formula. The minerals in well water, for example, can form a chemical bond with phosphates to form a scale that can affect the transfer of heat. The best mixtures will include de-mineralized water.
Users should also be aware of the base glycol that is found in any formula, Turcotte says, noting how ethylene glycol and propylene glycol each feature a different density. That will change the freeze point. “Ethylene glycol is the dominate choice but propylene glycol has a presence in heavy-duty applications, especially in food service or environmentally sensitive applications.”
THE RIGHT TOOLS, TESTS
For teams in the shop, the best tools to ensure a proper chemical balance in the cooling system will come in the form of test strips and a refractometer.
Test strips are available to measure everything from the fluid’s freeze point to the levels of molybdate and acidity, but the choice of the test strip will be dictated by the type of coolant.
“If you’re using a conventional coolant, you have to have one for nitrite or nitrite-molybdate,” Granger explains. And an inspection of a long-life coolant’s freeze point will ensure that workers are not topping off reservoirs with too much water, so that cylinder liners enjoy the proper level of protection.
Even in a coolant without nitrites, the test strips serve a purpose. “You can confirm that you have the right dilution and that will tell you the additives are there in the appropriate amount,” Turcotte says, referring to the importance of maintaining concentrations and freeze point.
A check of pH levels also can identify early issues with blow-by gases from the combustion process, Ulabarro says. “If a coolant changes more than 2 pH units from its original form, it’s telling you that something’s going on.” The only challenge here is that shops need to know the pH level that existed when the coolant was first added.
Just be aware that test strips of every sort will come with best-before dates that will have an impact on their accuracy, Granger says.
Meanwhile, a simple refractometer is the best tool for measuring freeze protection, he adds. That way, nobody has to worry about determining the color on a test strip. “With a refractometer, you read the scale and it’s pretty straightforward. There’s little source for error.”
He offers another tip: When looking for an accurate reading and the freeze point is at the top end of the scale, simply take a sample and dilute it with 50 percent water. Widely available charts will calculate the shift in the readings.
The good news for shops is that existing coolants are expected to meet the needs of engines that are designed to meet the U.S. EPA’s requirements for 2010. Even with the introduction of exhaust gas recirculation systems, bulk coolant temperatures have remained relatively unchanged as long as the water pump and thermostat are working like they should.
Once the lessons are learned, they will still apply.
