Truck Topics

Do You Really Know Your Cooling System?

If you're a conscientious expedited owner-operator who takes good care of his truck, are you being comprehensive in your PM's?

Sure, you keep your oil and filter changes up to date, but how often do you check your coolant's "health"?  A checkup on your cooling system is as much a part of PM as any other system on the truck.
 
The experts tell us that maintaining proper coolant protection is vital to an engine’s longevity.  Studies show about 40 percent of engine maintenance is related to cooling system failures. Those same experts also say that cooling system failures are almost 100 percent preventable, but coolant must be maintained the way its manufacturers intended.

The two prime causes of coolant deterioration, other than time and heavy use, are chemical contamination and using the wrong mixture when topping off the system.

Chemical contamination results from running a diesel engine with wet cylinder liners, which causes tiny amounts of impurities to seep into the coolant through the seals.

One service manager estimates it could add up to a $10,000 bill or greater to replace pitted liners because the worn-out coolant didn't protect the liners from corrosion.

The biggest concern in coolant maintenance however, is deciding which antifreeze and how much water to use in replacing leakage.

The largest single ingredient in coolant is ethylene glycol, which, when equally mixed with water, lowers the coolant’s freezing point to minus 34 degrees Fahrenheit.

Failure to use coolant can cause your engine to freeze during extreme cold, wreaking havoc on your engine. But using too much coolant and not enough water can reduce the ability of the coolant to remove heat from the engine, which also causes problems. 

Coolants now come in two types: conventional antifreeze and Extended Life Coolant (ELC).

Conventional antifreeze uses nitrites and borate inhibitors to protect metals.  While this works just fine, the inhibitors can break down in hot, corrosive environments.  For that reason, conventional antifreeze requires periodic replacement of the inhibitors with supplemental coolant additives, or SCAs.

The newer product is Extended Life Coolant, now made by all major oil companies.  ELCs use organic acids called carboxylates to protect the metal surfaces.  Carboxylates are more stable than SCAs and can last longer with the addition of a small bottle of extender about halfway through their life.  ELCs can be used up to 600,000 miles or more with the use of an extender at 300,000.

Since ELC doesn't use conventional abrasive inhibitors like silicate and phosphate it will help avoid silicate drop out, which clogs coolant passage ways, reduces water pump seal failure and improves maintenance costs because of longer service intervals.

Although ELC is compatible with conventional coolant, mixing the two will reduce the benefit of extended life coolant.
 
Heath Wood, Sales Manager at Middle Georgia Freightliner-Isuzu in Macon, GA is a trained diesel technician who says, "I think the ELCs are a viable product.  When you have the trucks rolling out of the factory with ELC in the radiator, you know that the OEM's have done their testing on it."

Here are a few ways to save money and downtime by taking a pro-active approach to maintaining the cooling system.

Inspect the whole system
A cooling system is more than coolant.  You should check hoses and tubes for soft spots, bulges, cracks, leaks, brittleness or other signs of trouble.  Check hose clamps to make sure they're tight and undamaged.  If the clamps need frequent tightening, switch to spring-loaded constant torque clamps.
     
Inspect the fan clutch and fan blades for proper operation.  Check drive belts for proper tension/wear and adjust/replace belts where necessary.

Inspect the radiator cap for a secure seal with the radiator and check the thermostat for proper operation. Make sure radiator shutters (if your truck is equipped with them) open and close at the correct temperatures.

Pressure test regularly
Pressure test the cooling system regularly. This can reveal any leaks and catch small problems before they grow. Some experts say it should be done once a year while others recommend that it should be performed during every PM.

Using a special pressure testing device, the system is pressurized to its maximum.  If there's a leak, pressure will drop.  Quite often, fixing these leaks is nothing more than tightening down a hose clamp.  The leak can be repaired now which saves you money because you won't be topping off with coolant on the road.

To cap it all off
Check the radiator cap with pressure testing because if the cap opens too soon or not soon enough, it may divert coolant to overflow prematurely.  The cap should be checked every 50,000 miles.

However, using the wrong pressure cap can damage your cooling system, especially if air gets into the system.  Air deteriorates the additives and nitrites in the coolant.

Test coolant on a regular basis
Cooling system care requires more than just "fill it and forget it" with the occasional top off.  This is one of the most common mistakes truck owners make when it comes to taking care of this system.  This guideline applies whether you're using traditional coolants or the extended life version.

Either type of coolant must be maintained at the proper ratio of coolant to water.  The typical mix is 50/50, and coolant levels lower than 40% should be avoided.  You can determine whether your system is protected by checking the freeze point with a refractometer.

Use extended-release filters
If you're not using organic-acid based extended life coolants (ELC), use fully formulated conventional ethylene glycol coolants with a controlled-delivery coolant filter that replenishes the corrosion inhibition chemistry as the coolant ages.
     
Even if you are using an ELC,  an extended-release filter specifically designed for use with these coolants can help ensure the chemical levels are where they should be, instead of waiting for the 300,000-mile extender that is part of the ELC package.

Keep the system full
Virtually every truck's cooling system will lose some coolant over time, because connections and hoses will invariably leak a little.  With modern engines, it's even more vital that the cooling systems stay topped off regularly with the proper coolant.