Cool it

Here’s what happens to those thin little radiator tubes when the cooling system isn’t properly protected. Just a little of this kind of clogging will raise the coolant temperature and soon cause radiator leaks.

Cooling systems are working harder than ever in 2007 engines because the nitrogen-oxide emissions limits dropped. For most manufacturers, this meant recirculating more cooled exhaust back into the cylinder to absorb heat during combustion.

Even Caterpillar, which opted out of exhaust gas recirculation in the 2002 round of emissions reductions, has joined the throng of exhaust eaters – though Cat’s Clean Gas Induction uses somewhat less exhaust and grabs it only after the diesel particulate filter has cleaned out the soot.

Today’s EGR cooler is bigger and absorbs more heat that is routed right to the radiator. Some of the engines may see more heat internally, but significantly more heat will be vented into the outside air.

Inside the engine, therefore, “There is more heat, but no more temperature,” says Ed Saxman, Volvo product manager for drivetrains. “A lot of people misunderstand that. They think it runs hotter, but it doesn’t.”

Indeed, coolant temperature limits and pressure cap requirements have not changed since 2002, says Cyndi Nigh of Cummins.

Here are the critical areas to watch in helping a newer engine keep its cool.

Air first, coolant second
All this extra airflow means your first concern in cooling system maintenance should be the air side of the radiator. Those closely spaced fins – only three-thousandths of an inch thick – catch dirt, so keeping the radiator clean both inside and out is vital, says Mike Masuch of Mike and Daughter Radiator Aid in Lancaster, Pa.

Outside cleaning must remove not only corrosive road salt, but plain old non-corrosive dirt, which reduces cooling efficiency. Dirt not only blocks the flow of heat from metal to air but reduces the amount of air passing through – and air is the only place for heat to escape.

Cooling problems always snowball and attack the radiator, Masuch says. Anything that interferes with the radiator’s ability to get rid of heat increases the operating temperature and pressure. The higher they are, the worse your corrosion and physical stress, which then tend to create radiator leaks.

Start at the front, Saxman says. Today’s engines all rely heavily on a charge air cooler up front; if it’s partially blocked, airflow through the radiator will be reduced. Cooler intake air also reduces the heat of compression in the cylinder and allows more air in, improving combustion. The heat either goes through the air cooler, or it ends up in the radiator.

“The charge air cooler is the most under-maintained part of the cooling system,” Saxman says. “You have to check the charge air cooler for bugs. The phenomenon depends on when and where you drive, but even with a bug screen you often end up with bugs whose bodies have been strained through the radiator, creating a goo that makes them stick like mad. Bugs in the charge air cooler can cause the engine to smoke and give poor fuel economy.”

While the cooler is off, carefully clean the radiator fins with a wire brush or radiator comb – something that will clean aggressively without bending the fins – and flush off any salt or mud with water. “You can’t just squirt a stream of water through with a hose,” Saxman says. “Periodically unbolt the air cooler and clean out the bugs. You have to mechanically get the bugs out because of the way they are stuck on.” This should be done every couple hundred thousand miles, Saxman says.

Fans and belts
While most water pumps today are gear driven, the engine fan is belt driven, with an on/off or modulating clutch. A fan not turning at full speed will allow coolant temperature to increase above normal when you are climbing hills at low speed, and may even cause overheating in traffic.

“Perform a daily check for obvious hose leaks, belt condition and coolant level,” Nigh says. Look for cracks, signs of fraying and that telltale smooth look on the vee surfaces that indicates slippage. Failing serpentine belts often will display cracks on the ridges between the grooves. Replace belts that show signs of wear.

Check the mechanical condition of automatic belt tensioners; on traditional systems, use a belt-tension gauge to ensure proper adjustments.

Keep your ears open for the sound of the cooling fan. If you notice a reduced sound, the fan is not turning as fast as normal, and the system needs repair. Check the belt tension and condition, remembering that belts worn smooth will slip even if properly tensioned. If the belt is OK but the fan is not turning fast enough, have the fan clutch rebuilt, or do it yourself.

Hoses and clamps
“Higher temperatures can affect hoses made of elastomers,” says Regis Pellet, senior staff chemist for Chevron Coolant Technology. “So check for signs of wear and tear on hoses. Make sure they are not starting to oxidize.” This would mean extreme softness, brittleness or cracks.

Make sure clamps are in proper condition and snug. The additives found in traditional coolant tend to fill tiny gaps at connections, but a switch to extended-life coolant may flush them out, removing the seal, Pellet says. If you suspect this, drain the system, disconnect the leaking hoses, thoroughly clean the connections and then reassemble. On the plus side, extended life coolants can clean the deposits left by repeated use of additives that retard head transfer. An engine free of these deposits will run cooler.

Cold water leaks often are caused by sediment that shows up when the system isn’t maintained properly, says Garret Funk, a regional manager with the Penray Cos., which makes additives that prevent the formation of sediment.

Coolant
The cooling system “is like a swimming pool on 18 wheels,” Funk says. “With water, you always need to control oxidation.” One byproduct of that oxidation can be scale deposits that insulate the engine from the coolant or keep the coolant from readily throwing off its heat in the radiator.

“More heat compounds problems,” Funk says. “The need for cooling system additives will then be greater.”

There are two rival types of coolant protection. The traditional approach uses supplemental coolant additives (SCAs) in conjunction with fully formulated antifreeze. SCAs – mostly nitrates, Funk says – form a protective film over the interior surfaces of engine and radiator. These gradually decompose with heat and need to be replaced. The traditional practice has been to adjust SCAs every oil change.

The newer approach is to use extended-life coolants. They contain carboxylates, which are much more stable than SCAs and don’t require replenishment. Most extended-life coolants require no addition of chemicals except the addition of an extender halfway through the life cycle: 300,000 miles for Caterpillar Extended Life and Shell Rotella ELC, which extends the life to 600,000 miles, and 500,000 miles for Chevron Delo and Texaco Extended Life, which extends the life to 1 million miles. The Chevron and Texaco brands are good until 750,000 miles with no extender. However, Pellet warns that you also need to maintain freeze protection to ensure corrosion protection. “What we recommend is checking the freeze point at least once every year and only top off with 50/50-ELC,” he says.

Some suppliers of conventional coolant make filters designed to add SCAs continuously and reduce maintenance. Penray’s Need-Release filter, for example, “actually senses the pH and releases the chemistry” in a controlled manner to maintain a constant level of SCAs, Funk says.

If you’re looking for other brands, ExxonMobil makes Mobil Delvac Extended Life Coolant/Antifreeze ELC and Exxon Antifreeze Plus fully formulated coolant. Detroit Diesel markets an extended life coolant called Detroit Diesel Power Cool Plus, good for 600,000 miles with the extender. Detroit also sells a version of the Penray Need-Release coolant filter called the Power Cool Need Release filter, designed to replace up to eight ordinary coolant filters and typically last 15 months or 120,000 miles.

Coolant protection was so good already that nobody has changed the testing, draining and flushing standards for 2007. More heat does mean, however, that diligence in remembering to change or add supplements on time is critical.

Maintenance and testing
Always replace any leaked coolant with the same type: extended life with extended life, fully formulated with fully formulated. Never mix the two or replace either with plain or automotive antifreeze.

The easiest approach is to always add a 50/50 premix to maintain antifreeze strength.
If you’re diluting full-strength coolant, make sure the water meets the engine manufacturer’s requirements for purity by having it tested.

Periodically having coolant analysis done, too, is good for quality control. “Testing means a safety net, just to check for the presence of oil or fuel or other major problems,” Powers says.

Like oil analysis, such tests cost a nominal amount, typically from $15 to $50, depending on the source and whether they are testing for dissolved metals.

If you have a small leak and can’t get extended life coolant, just add water because it provides ideal heat transfer, Pellet says. Then adjust as soon as possible to prevent freezing by adding full-strength coolant until freeze protection is back to 50/50. The most precise method is to use a refractometer, a device that bends light in order to indicate freeze point on a temperature scale. Look for 34 F, says Pellet.

Chevron is one of several brands that offer tests of extended-life protection. Shell offers an ELC Contamination Test Strip Kit to test for satisfactory carboxylate inhibitor content, in the event a driver may have replaced lost coolant with something other than ELC. Diluting Shell Rotella ELC by more than 15 percent will require the system to be drained and refilled or treated with SCAs, Shell says.

Penray’s TS-200 “gives a pass or fail indication,” Funk says. If you add the right stuff and replace the need-release filter at proper intervals, Penray’s system nearly eliminates playing with SCA levels. Still, Penray recommends testing for antifreeze strength (which can be done with test strips) and protection levels at conservative oil change intervals – just in case.


Unpacking heat
There’s no single answer to removing the additional heat created by increased exhaust gas recirculation. Manufacturers “are using a combination of various radiator and charge air cooler sizes and configurations, different fan configurations, etc., to determine the best solution for the truck model and application,” says Mike Powers of Caterpillar.

Volvo has redesigned its grille to ease airflow and replaced the 28-inch fan with a 32-inch version, says Volvo’s Ed Saxman. Also, the D13 engine has its camshaft drive at the flywheel rather than at the front of the crankshaft.

“The front of the engine got a lot thinner,” Saxman says. “The amount of airflow around the engine at the front is up considerably. We have found that the fan runs on average only about 1.5 percent of the time.”

Cummins has increased the front area of the radiator and charge air cooler, improved the fit and baffling of the fan shroud to reduce air leaks, reduced airflow restrictions through the radiator and charge air cooler, and increased water-pump flow, spokeswoman Cyndi Nigh says.

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