When heavy diesel emissions control systems were first introduced (could it be only five years ago?), just about everyone in the trucking industry was concerned.

Fleets were asking if the systems would even work, and if they did, what problems and additional expenses would they bring? Truck manufacturers might know these engines were going to generate additional heat and were very concerned about the problems it would cause. Even cooling system experts were worried. “The primary concern before the introduction of EGR systems in 2002 was whether the coolant would survive the spiking of temperatures it would experience where the exhaust entered the pre-cooler,” says Darrell Hicks, a recognized member of the Technology and Maintenance Council and owner of Darrell Hicks Enterprises, an experienced cooling system supplier to the trucking industry.

In a similar way, Donaldson Co.’s Matt Stein describes the results of engine design changes made in response to emissions regulations by saying, “The increased use of EGR, tighter engine packaging and other engine strategy changes have combined to create an environment where engines sometimes operate at higher temperatures. This makes it more important than ever to make sure coolant systems are functioning properly.”

Stein’s colleague, Keith Bechtum, the company’s engine liquid product specialist, agrees, saying, “Because engines are running hotter, it’s more important to make sure the cooling system is properly maintained, because you’re asking the system to do more, and you’re depleting the additives faster.”

System components
It turns out that the concerns were well-founded but quite properly ad-dressed by cooling system design engineers. Hicks says, “As long as the coolant continued to flow, had the appropriate antifreeze/water ratio and the correct pressure cap; the concerns were not realized. It truly became a ‘non-event.’”

Properly spec’ed cooling system components also contributed to this “non-event.” Gates Corp. engineers, for example, discovered what you can’t see can hurt you. During long-term field tests, they identified the primary cause of coolant hose failure as an electrochemical attack on the rubber inside the hose. This can result in very small cracks in the hose tube allowing the coolant to attack and weaken the hose reinforcement. Accelerated by heat and flexing, the hose can develop a pinhole leak or actually rupture. To solve the problem, Gates developed an electrochemical-resistant hose using a ethylene propylene (EPDM) formulation inside and a special wrapped reinforcement. In addition to chemical resistance, EPDM hose offers superior bonding to metal fittings –– compared to either standard rubber or silicone hoses –– that helps to prevent coolant leaks.

However, if continuous service over 275 degrees F with temperature spikes over 300 degrees F are common, Gates engineers say that silicone hoses are still the best choice. When using silicone hoses, remember to use constant tension (spring) type clamps, constant diameter (worm drive) clamps with an inner protective band, or thermoplastic hose clamps. These designs prevent the soft silicone rubber from extruding through or under the clamp.
Make sure your cooling systems retain the correct caps. Hicks says, “Pre-emissions controlled engines ran very successfully with seven to ten PSI pressure caps. One of the moves that helped coolant survive was to raise the pressure on cooling systems to 15 PSI. For every pound of pressure increase, you get three more degrees of protection from boiling.”

Coolant
Baldwin Filter engineers tell us of the various functions required of an engine coolant:
• Removes heat
• Lubricates components (such as water pumps)
• Provides freeze protection
• Prevents scale and sludge formation
• Protects against corrosion

The first three functions can be accomplished by a simple mix of a low-silicate antifreeze and water. Additional chemicals, such as supplemental coolant additives (SCAs), must be introduced to the system to prevent scale and sludge formation and to provide corrosion protection. SCAs typically contain inhibitors designed to prevent generalized corrosion, as well as cavitation erosion; polymers that keep hard water scale from depositing on engine surfaces and buffers to reduce the acidity of the coolant.

Before the introduction of emissions-controlled engines, most fleets successfully used conventional coolant –– ethylene or propylene glycol antifreeze and water –– in their engines, although even then some fleets were moving to extended life coolants. Since then, a number of different coolants have been introduced to the industry.

Figure 1, provided by Chevron, shows the minimum requirements for ensuring that various kinds of coolants are maintained properly. Any heavy-duty coolant –– conventional, hybrid or extended life coolant –– can be expected to fulfill engine manufacturer requirements as long as it is intended for use in heavy-duty engines and not designed for use in automobiles. Donaldson’s Bechtum says, “Each comes with both advantages and disadvantages relative to cost, life and maintenance requirements. Traditional coolant is a low-cost option but requires the most maintenance. On the other end of the spectrum are organic technology products, the long-life or extended-life coolants. These come at a premium price but require less maintenance. Hybrid coolants fall somewhere between those two.”

While it’s really up to you to choose a coolant that will fit best with your maintenance practices, engine manufacturers like to see fleets use extended-life products because they lessen the chance that maintenance will be overlooked. Mike Powers, product design engineer for Caterpillar Inc.’s on-highway engine group, says, “We recommend the use of long-life coolants because they almost eliminate cooling system maintenance; for example, SCA testing and all that goes along with it. As customers have moved to extended-life coolants, it has helped minimize cooling system maintenance.”

If you choose to actually perform in-service tests on coolants, it’s important to thoroughly clean the cooling system between using the various coolant products. The National Automotive Radiator Service Association (NARSA) says, “Over time the metal surfaces in the cooling system will be etched by the original coolant and retain the chemical makeup of that coolant. When a system is converted from the original coolant, the chemistry in the system stays the same and the properties of the new coolant are overridden by the chemistry of the original coolant.”

George Sturmon, chairman of Envirocool, echoes the warning saying, “All of these new coolant packages deposit a film on cooling system surfaces. When you go from one coolant to another, it’s very important to completely clean out the system. If you don’t, the previously deposited film will affect the performance of the next coolant.”

Maintenance
Data indicates that different maintenance practices are required for the various kinds of coolants. Knowing exactly what’s in the engine is therefore very important. Brad Drake, a technical writer for Wix Filters, says, “It is absolutely critical that you know what coolant you are using, and, unfortunately, you cannot be certain based on its color. Coolant coloration has generated a lot of confusion in the industry. When you look at the array of colors, it’s clear that not everybody is singing from the same sheet of music.”

Until rather recently, the color of the most commonly used antifreezes for both light-duty and heavy-duty cooling systems was green. Then, long-life coolants were introduced in an effort to reduce maintenance costs, downtime, and environmental disposal costs and issues. With the introduction of this new concept, antifreeze manufacturers wanted to differentiate this new product from existing antifreezes. To accomplish this, they introduced different colored dyes. Orange and red dyes were used first. Now it appears there may be virtually no limit to the different dye colors that may be used.

Drake says, “If you come across an unknown coolant, the best practice is to flush the system and install your choice of coolant. Using ‘universal’ coolants is a mistake. Manufacturers claim that such coolants are compatible with any product, but the results are pretty unpredictable. Some fleets supply a container of premixed coolant for topping up when the truck is away from the shop.”

The use of filters and cleaning cooling systems is highly recommended. Envirocool’s Sturmon says, “Over half of all premature engine failures are due to cooling system problems, and 80 percent of those are caused by contaminated coolant. Cleaning the system may sound too simple, but it works.”
The internal walls of EGR heat exchangers can run as high as 600 degrees F. That’s high enough to affect any kind of coolant. At such temperatures, the coolant itself can break down. Sturmon says, “There are a lot of black deposits inside radiators. I’ve had some of that material analyzed and have found it to be burned glycol.”

While cooling systems are basically the same as they were a decade ago, it’s more important than ever to make sure they are properly maintained because new engines are running hotter and so deplete additives faster. For best results, it helps to follow these tips:

• Keep the outside of the radiator clean.
• Make sure the correct radiator cap is being used and is operating properly.
• Check the condition of the coolant with a refractometer.
Good maintenance will help keep concerns about cooling systems a “non-event.”  

 

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Check the Coolant

Pointing out that cooling system health begins with the coolant, Peterbilt offers these coolant checks.

Keep the glycol level at the manufacturer’s recommended ratio for your operating conditions. For instance, for freeze protection at -30 degrees F, the mixture of glycol to water is typically 50:50. When taking readings, a refractometer should be used.
Keep nitrate levels at the manufacturer’s recommended levels, usually between 1,200 and 4,000 parts per million, and keep acidity/alkaline levels at the manufacturer’s recommended levels, typically between 8.5 and 10.5 pH.

Use coolant test strips at every oil change interval when using conventional coolant. They are dipped into the coolant through the radiator opening and will indicate ratios of glycol and nitrates, helping to keep them in proper balance.
Use distilled water in the system to help prevent mineral deposits.

 

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Cool Logic fan drives provides heavy-duty cooling

Borg Warner says that its Cool Logic heavy-duty, multi-speed fan drives are a breakthrough in engine cooling technology. Not only are they electronically controlled and maintenance-free, but also they provide improved fuel economy while meeting the needs of the stringent North American heavy duty truck emissions requirements.

The fan drives feature electronic modulating speed control. This means precise temperature control all the time, extending the life of the entire cooling system including the radiator and charge air cooler. Couple that feature with the fuel saving fan speed control scheme and the maintenance-free design, and you’re well on your way to cool savings, the maker says.

What’s happening in the cab is just as important as what’s under the hood, the company says. Cool Logic’s actuation logic system means quiet operation for a more comfortable ride, the maker said.

According to Borg Warner, the heavy-duty, multi-speed fan drives are a breakthrough in engine cooling technology. They are electronically controlled and maintenance-free, and they provide improved fuel economy while meeting the needs of the stringent North American heavy-duty truck emissions requirements.

The fan drives feature electronic modulating speed control, which means precise temperature control all the time, extending the life of the entire cooling system including the radiator and charge air cooler, the company says.

fig 1
Coolant Maintenance Recommendations

Coolant Type	Maintenance Required	Recommended Change-out Interval
Conventional Coolant	1. Minimum quarterly testing with test strips to evaluate inhibitor levels    2. Depending on service severity, re-inhibition with supplemental coolant additives (SCAs), generally quarterly  3. Freeze-point testing twice per year	Every 2–21/2 years
Fully Formulated Coolant	1. Minimum quarterly (every 500 hours) testing with test strips to evaluate inhibitor levels       2. Depending on service severity, re-inhibition with SCAs, generally quarterly. These types of coolants may require fewer SCA additions depending on the amount of top-off used.       3. Freeze-point testing twice per year	Every 2-21/2 years
Hybrid Coolants	1. Testing generally once per year for inhibitor testing         2. SCA addition generally once per year 3. Freeze-point testing twice per year	Dependent on the manufacturer, generally between four to six  years.
Extended Life Coolants	1. Top up with ELC          2. Freeze-point testing twice per year	Generally six to eight years. Some manufacturers require an extender for extended product service life.