A checkup on your cooling system is as much a part of winterizing as digging out your wool socks, and with 2007 engines on the horizon, it's a good time to start thinking about this oft-overlooked system.

What effect 2007 engines will have on engine coolant in the long run is not yet known. While there has been much talk about the new low-emissions technology potentially producing more heat, coolant makers differ on what that effect might be. They are carefully monitoring coolant performance in engine testing.

"We know with EGR [in 2002/04 engines], the coolant itself had to handle higher heat loads from contact with the cylinder liners and the EGR cooler," says Jim Roberts, technical service manager for Shell. "That leads to more localized boiling and hot spots and potentially reduced coolant life. And of course in 2007, when we go to even heavier EGR, we think that's going to affect the coolants even more."

He says samples of used coolant from EGR engines have shown more rapid degradation of the ethylene glycol (it's a hydrocarbon, and hydrocarbons tend to degrade when exposed to heat), as well as more rapid depletion of nitrite, the main additive used to protect wet sleeve liners against cavitation corrosion.

Paul Fritz, senior coolant technologist for Chevron Global Lubricants, echoes Roberts' concern about hot spots in areas such as those around the EGR cooler, and also brings up the possibility of higher under-hood temperatures. The higher under-hood temperatures may begin to shorten elastomer and hose life, and at the hot spots, he says, glycol can break down faster, which could build up acids and lower the pH. "We haven't seen that yet, but that's what we look for."

At the same time, optimized vehicle aerodynamics – in greater demand than ever as fuel prices soar – restrict the frontal air flow of the radiator, says Brent Birch, laboratory manager for Champion Laboratories, which makes Luber-finer filters. "To compensate, other aspects are enhanced as a system, such as core thickness, fans, fan clutches and management, ducting, thermostats, higher coolant flow rates, etc."

Despite all this, John Clevenger, director of global products for Cummins Filtration (formerly Fleetguard), says there is no increase in the temperatures in the new engines. "[OEMs] are offsetting potential additional heat in the engine by increasing coolant system size, increasing fan speeds, using higher-efficiency EGR coolers. All the OEMs I've spoken to or seen publicly state, they've all said there is no 2007 coolant system temperature increase at all."

The only thing that's certain is that there's not enough experience yet to know if there are going to be any issues with coolant in 2007 engines. So far, coolant manufacturers say, they haven't seen any problems, and don't really anticipate any, especially with extended-life coolants. Extended-life coolants offer more thermal stability, and they don't depend totally on nitrite to protect the wet sleeve liners.

Penray has been looking at hundreds of coolant analyses for the last 18 months of 2007 engine testing, and says it hasn't seen anything that looks like a problem – no accelerated degradation of the coolant, and the inhibitor packages in both extended life and fully formulated coolants have held up to the higher heats generated.

It is possible that recommended service intervals could be affected. Extended-life coolants last 600,000 miles or longer, and no one has yet accumulated those kind of miles on a truck with a 2007 engine, so there's no way to know for sure. For traditional coolants, more rapid nitrite depletion may mean a need to add supplemental coolant additives (SCAs) more frequently.

There does seem to be some agreement that extended-life coolants may be better able to face potential challenges. "In our testing, we see that [they] tend to be more protective at the higher temperatures; we see less breakdown products," says Chevron's Fritz. "The way conventional coolants protect, they work almost like paint – they put down a layer that insulates the metal from the coolant. But just like a paint, as you go to higher and higher temperatures, you can imagine paints can blister off, and that is what can happen with these layer-forming inhibitors. At higher and higher temperatures, they can break down."

Whether or not heat proves to be an issue, Clevenger says, the 2007 engines do mean you should pay closer attention to your coolant and cooling systems. "Most of the systems are 20 to 30 percent higher in capacity, so you've got more coolant to deal with. So the coolant system's going to be as important or more important than it was before."


Extended-life coolants are becoming a more popular option as fleets look for ways to extend service intervals and take the burden off hard-to-find technicians. Many truck manufacturers are now factory filling standard with extended-life coolants. These coolants, while more expensive up front, can offer cost savings in the long term.

While all antifreeze products use a glycol base, which is mixed with water to produce coolant, it is the additive package that makes the difference, with various ingredients battling corrosion, keeping pH at the proper level preventing foaming, etc.

Traditional coolants use silicates, phosphates, nitrites, borate, molybdate and other inorganic chemicals to lay down a protective layer over the metals and materials in the cooling system. These additives deplete, and more must be added on a regular basis.

Newer extended-life coolants use what is called carboxylate or organic acid technology. (They're not really acids, so don't be put off by the thought of putting acid into your engine.) These additives deplete much more slowly than traditional chemicals because they chemically react only with metals that are in danger of corrosion, putting down a protective layer at the molecular level. Most of these products will last 600,000 miles if you put in an "extender" with additional inhibitors at 300,000 miles.

Extended life coolants save you time and money not having to test the coolant for additive levels and constantly add SCAs. In addition, proponents say, they offer improved heat transfer, better liner protection and longer life of cooling system components.

"We did a teardown on some vehicles with 750,000 miles that were factory filled with extended life coolant," says Chevron's Fritz. "Of the five trucks we tore down, two still had the original water pump, which is really unheard of. The other three, the water pumps were replaced after half a million miles. It wasn't too long ago that it was standard practice to change out the water pump at 200,000 or 300,000 miles."

(Not everyone agrees that water pump life is the exclusive benefit of using extended life coolants. Dean Swick, OEM sales and account manager for Penray, says a good fully formulated coolant works just as well as extended-life coolant. Cummins' Clevenger notes that a coolant filter is an important factor in reducing the particles that kill water pump seals.)

One perceived disadvantage of extended-life coolants is the need to top off only with the same coolant to avoid "contaminating" the system. A better term is actually dilution. A small amount of non-ELC antifreeze in the system isn't going to harm the protective effects of an extended-life formula. But just like traditional coolant, if you dilute it enough with water, or with coolant that doesn't contain the same kind of additives, those additives will lose their effectiveness. Depending on who you talk to, that tipping point is around 20 to 25 percent.

Adding to the confusion, extended-life coolants are not all alike. There are different types of organic acids, with advantages and disadvantages to each type. In addition, ELCs vary in the amount of organic and inorganic chemistry they use. Many extended-life coolants contain not only the carboxylate/organic acid technology, but also some of the inorganic, conventional inhibitors, most commonly nitrite. Whether or not these are considered "hybrids" depends on who you're talking to.

"We have the extended-life coolants, but we also have hybrid organic acid coolants, which are new and are making their way into the marketplace," says Penray's Swick. "They rely on the best of the both worlds for cooling system protection." Because they are phosphate-free and low in silicates, he says, "we're not seeing the dropout or goo concerns" that were a problem with conventional inhibitors. Phosphates, he says, are one of the biggest culprits in dropout. "Without the presence of phosphates, you see virtually no trouble caused by the silicates."

In reality, Clevenger says, "just about everybody in the [extended- life coolant] market is basically selling a hybrid. Most of the additive packs have enough nitrite in there that even if the organic acid didn't do its job, you'd still have liner-pitting protection."

However, there are companies that advertise extended-life, organic acid products as being free of these chemicals. BP, for instance, advertises its Castrol Heavy Duty extended-life coolant/antifreeze as free of phosphates, silicates, nitrites and borates.

Star Brite, a company that has been marketing chemicals to the marine and automotive markets for years, recently introduced an extended-life coolant for heavy-duty engines it says is a pure organic acid chemistry, with no nitrites, phosphates, borates, silicates or other inorganic additives. Star Cool lasts for 750,000 miles with no extenders, according to the company. It can do this because it uses a different type of carboxylate chemistry than others on the market, says Vic Brown, national sales manager.


Earlier this year, Chevron announced that its new Extended Life Coolant formulation will protect cooling systems of on-road vehicles for 750,000 miles without an extender and a million miles if chemical extender is added at 500,000 miles, nearly doubling the recommendations from most extended-life coolant makers.

In reality, with the proper maintenance program, many extended-life coolants can go beyond the usual 600,000-mile life, just as many fleets extend their oil drain intervals using oil analysis.

"True organic additive technology coolants, when properly maintained, can go out to a million miles," say Shell's Roberts. "We've maintained all along on our Shell Rotella ELC that the recommended service life is 600,000 miles, but if at that point you have a sample analyzed [and the numbers are good], you can continue on well beyond that."

Chevron's Fritz explains that while they did make some changes to the formulation, "really, the big jump in claims is based on more experience we've had with the product as well as better ways to test coolant in the field."

While extended-life coolant manufacturers recommend against regular testing of coolant as you do with traditional formulations, it is necessary in certain situations, especially if you want to extend service intervals beyond the recommended point. Instead, they recommend testing the freeze point at least once a year, and preferably twice, to make sure the antifreeze/water concentration is still at the recommended ratio (typically 50/50). Testing for additive dilution should be done if there's reason to suspect a problem or you want to see if you can leave the coolant in longer. There are different types of testing available, including a paper test strip; a two-step process where you put a small amount of coolant into a vial, shake, then test; and sending coolant off to a lab for full analysis.

The paper test strips are a recent development, with Penray announcing strips that can be used for traditional or extended-life formulations. After identifying that you're dealing with extended-life coolant, you dip the test strip in the coolant, shake off excess coolant, wait about 45 seconds for it to react, then compare it to the test strip bottle.

In the past, says Penray's Swick, "there was no way to determine if there was contamination on the road – did the driver put water in, did he choose the wrong coolant to top off? If that goes undetected, that can result in engine damage. The biggest horror story are the people who rely on extended-life coolants and the driver puts water or another coolant in, and no one knows about it until we have liner pitting and a $10,000 overhaul. And it does happen frequently." The good news is, extended-life coolants are more readily available in truckstops than they were when initially introduced. And while it's best to use the same brand, especially to make sure you don't void any warranties, using another brand of extended-life formula is better than topping off with traditional coolant.

Some experts are skeptical of the paper strips. Shell's Roberts notes they don't actually measure the organic inhibitors. Some people complain the two-step vial process is too hard, but he says, "You've got technicians that are rebuilding engines, and it's too hard for them to squirt 5 milliliters into a vial and shake it up? No, it's not as simple as dipping a nitrite strip into a radiator, but then again, you don't have to use it as often."

Clevenger says one problem with developing paper test strips is that there are many different organic acids being used in extended-life coolants, and one strip may not accurately test all types. Because extended-life coolant formulations vary, it's best to check with your coolant supplier about which method they recommend.

If you do find the coolant has been diluted with other types of antifreeze, it doesn't mean you have to drain the system and put in entirely new coolant. You often can simply drain some of the contaminated coolant and add enough fresh to restore the right concentration of additives, which can now be more easily determined through the new testing methods.


How do you decide which type of coolant is right for your operation? You need to consider questions such as how often you see your trucks, how the coolant maintenance matches up with your other maintenance intervals, the conscientiousness of your technicians in maintaining the proper chemical and freeze point levels, what your engine manufacturer(s) recommends, and cost/benefit tradeoffs.

"Do some due diligence up front," Clevenger says. "Bring suppliers in to talk about their products, try to consider the pros and cons of each one, ask them for data to back up their statements, and try to make a determination about what's the easiest and simplest for you to maintain."

And once you've made a decision, stick with it, he says. "Changing around chemistries all the time confuses your maintenance people, and you lose the ability to track how what you're doing affects your maintenance costs."

If you decide to standardize on extended-life coolants, companies have made it easier and more cost-effective to do so. The best way to convert a truck from conventional to extended-life coolant is to drain and flush the system, then re-fill with the new coolant. However, that can get expensive, and many fleets are finding it's more cost-effective for them to use a conversion kit, where you add a super-concentrated blast of extended-life coolant to the system.

Doing this allows fleets to have only one type of coolant in the shop. For new trucks coming in factory-filled with ELCs, they'll enjoy all the advantages of the technology, Fritz says. For the other trucks, they will get some of the advantages of the extended-life formula, including cost savings not having to add SCAs. But, they may or may not see improved hardware performance.


Studies show about 40 percent of engine maintenance is related to cooling system failures. The thing is, it needn't be that way. "Cooling system failures are virtually 100 percent preventable, but you need to maintain coolant the way it was designed to be maintained," says Dean Swick, OEM sales and account manager for Penray.

1. Know what type of coolant is in the engine and what you need to do to maintain it. Even extended-life coolants are not "fill and forget." The freeze point needs to be checked at least once, preferably twice, a year, and a visual inspection can determine whether further testing should be done for dilution with other types of antifreeze. Putting the right type of coolant in at top-off will ensure your engine is protected and you get all the benefits of organic formulas. To make this easier, standardize on one coolant.

2. If you're going to use traditional inhibitor technology, consider using fully formulated coolant rather than relying on your technicians to be chemists.

"I've told people this for a long time," says John Clevenger, director of global products for Cummins Filtration. "You wouldn't go out and buy a base oil, buy a separate additive pack and tell your guys to mix it in. Why take that approach to the coolant system, which touches every system – oil, fuel, exhaust gas recirculation – and can impact every one of those systems?"

Jim Roberts, technical service manager for Shell, reports that two of the biggest problems his company sees when looking at used coolant samples are over- or under-concentration of the antifreeze in the coolant system, and over- or under-concentration of SCAs, primarily over-concentration.

"People hate the concept of buying water," Roberts says, "so they think they're getting a better deal buying concentrate and mixing it. When you're buying a 50/50 premix, you always know you're putting in the right amount of coolant with the right amount of water, and it's good water, and you're always within a few percentage points of where you should be on your concentration.

"When we've converted fleets over to a 50/50 mix, some of these fleets would have 80, 90 percent antifreeze in their cooling systems because they kept topping off with concentrate." Too many silicates can cause silicate gel, or "green goo." Too much nitrite can lead to problems with your radiator, such as solder bloom, different types of attacks on aluminum. "It's like when you keep putting too much sugar in your tea, it's going to fall out to the bottom of the glass. In your truck, the bottom of the glass is the water pump and radiator. Those solids collect down there and cause water pump seal wear and plug your radiator."

3. Use a coolant filter. With the advent of extended-life coolants that don't need SCAs, some fleets and even OEMs have stopped using coolant filters, believing the primary purpose of the filters is to add time-release chemistry to the coolant rather than actual filtration. Filter manufacturers say that's a mistake.

"The coolant filter is on there because the coolant system has about five times the flow rate of your oil system," Clevenger says. "It's there to take out core sand, rust, corrosion particles, rubber from the pumps, all kinds of things going on in the cooling system, because all that creates wear."

Clevenger says problems such as water pump failures and thermostat failures can often be traced to contamination that a filter could have prevented.

In fact, he says, coolant filters may be more valuable than ever with the 2007 engines. "When you increase the cooling system size, with larger radiators, bigger pumps, an EGR cooler, now you've got more seals, more soft metals, all kinds of things that can contribute to particulates in the cooling system."

While the physical size of most coolant filters has remained about the same, says Brent Birch of Champion Labs, makers of Luber-finer filters, many offer greater contaminant holding capacity than in the past, using specialized synthetic materials in the filter element.

4. Consider using coolant analysis, just like you do oil analysis. Polaris Labs, which does oil, fuel and coolant testing, says testing coolant twice a year at a lab can help prevent the large number of engine failures that are attributed to cooling system problems. For instance, in addition to determining things such as proper freeze point and additive levels, a coolant analysis program may identify problems such as electrical ground problems, combustion gas leaks, air leaks and localized overheating.


Chevron's Lubricants University (www.lubricantsuniversity.com), an educational web site focused on lubrication and coolant issues, has introduced a new online course, "Fundamentals of Heavy Duty Coolants."

The site offers web-based, self-study courses designed for maintenance professionals interested in ongoing training.

"Fundamentals of Heavy Duty Coolants" covers the operation of engine cooling systems, including parts, potential problems and the benefits and drawbacks of the various conventional and extended-life coolants currently available on the market.

Courses are available to the general public and cost $59.95 each. A subscription program is available for companies interested in offering training to multiple employees. All Lubricants University courses offer a certificate of completion once a student has successfully completed the training.