Be Really Cool

| May 13, 2002

The keys to cooling system maintenance are simple. Never mix, never worry. And when it comes to coolant, care and consistency matter most.

You need to maintain your coolant for the same reason you change your oil: proper protection. Engines burn fuel, but fuel does not burn perfectly and at least some hostile stuff (like acids) ends up in the cooling system. Why? Because engine seals don’t work perfectly. This contamination causes corrosion and scale formation.

The front line of defense in your cooling fluid are SCAs, Supplemental Coolant Additives.

The purpose of SCAs or the organic acid used in Extended Life antifreeze, is to form a layer of chemical protection against corrosion and scale on the cylinder liners and other metal surfaces in the cooling system. Unfortunately, the protective layer decomposes as the engine runs.

Watch the water
Tap water is contaminated with dissolved minerals. But the SCAs or organic acids that protect the cooling system have to be dissolved in water to work. In fact if they aren’t dissolved, they will form a destructive grit that causes trouble with water pump seals.

Consult your OEM owner’s manual for a table that lists tolerable levels of sulfates, chlorides, iron, and other impurities – and the pH value (acidity) – of approved water. Then, either buy distilled water that passes all the tests, or have your tap water tested through a dealer or laboratory so you know it’s OK to use. Many brands of antifreeze come pre-mixed with pure water, which solves this problem.

Don’t use too much antifreeze. The ideal mix is 50/50. If you need to go beyond that, use only as much antifreeze as you need for freeze protection, observing OEM recommendations for the maximum percentage. Remember that while a good mix cools well, antifreeze by itself won’t cool the engine properly.

The chance of mixing the wrong proportions of water and glycol is another reason to just buy pre-mixed.

What kind of antifreeze?
The two basic types of antifreeze used in heavy diesels are ethylene-glycol and propylene-glycol. David Strauss, an instructor at the North American Institute for Mack and Volvo, says the latter is sometimes used where coolants heat trailers that carry food products, as it is less poisonous, and more environmentally compatible in case of spills. Some manufacturers (like Volvo) prohibit the use of propylene-glycol, while others, like Caterpillar, limit its use to a 50/50 maximum because it does not cool as well as ethylene-glycol.

You must use a “low silicate” antifreeze approved for use in heavy-duty diesels. Coolant meeting ASTM 4985 standards is okay for most manufacturers, as it has nothing destructive in it, but you will need to add SCAs. The smart thing to do is to use a “fully-formulated” coolant that meets the TMC RP-329 standard (for propylene-glycol, the designation is TMC RP-330). Some manufacturers, like Detroit Diesel, only recommend the use of fully-formulated coolant. Since choosing fully-formulated as your initial fill gets you started on the right foot, and, when used to top the system off normally leaves it perfectly balanced, there’s usually little reason to consider using anything else.

An unprotected cooling system can allow scale to form on the outside of the liner. By holding heat in, the scale can cause the lube oil to get too hot and thin out. The result can be damage to the piston, rings and liner that looks like a lubrication failure.

What happens?
A couple of things happen to coolant as it ages. First, the additives gradually deplete as they break down in the act of protecting the metal parts of the cooling system. Second, small amounts of coolant normally leak out of the system and are replaced. The question is: With what? The biggest problem of cooling system management is controlling what goes back in.

Every driver should know what kind of coolant is in his engine, and he should replace only with the same kind. It’s ideal for the driver to carry the right replacement coolant, pre-mixed with approved water, along with him.

Coolant concentration may also change slightly because some types of coolant hoses will let water out but retain glycols. Too much glycol or too much water can easily be corrected with approved water or concentrated (rather than pre-mixed) coolant.

Be Really Cool

| May 13, 2002

The keys to cooling system maintenance are simple. Never mix, never worry. And when it comes to coolant, care and consistency matter most.

You need to maintain your coolant for the same reason you change your oil: proper protection. Engines burn fuel, but fuel does not burn perfectly and at least some hostile stuff (like acids) ends up in the cooling system. Why? Because engine seals don’t work perfectly. This contamination causes corrosion and scale formation.

The front line of defense in your cooling fluid are SCAs, Supplemental Coolant Additives.

The purpose of SCAs or the organic acid used in Extended Life antifreeze, is to form a layer of chemical protection against corrosion and scale on the cylinder liners and other metal surfaces in the cooling system. Unfortunately, the protective layer decomposes as the engine runs.

Watch the water
Tap water is contaminated with dissolved minerals. But the SCAs or organic acids that protect the cooling system have to be dissolved in water to work. In fact if they aren’t dissolved, they will form a destructive grit that causes trouble with water pump seals.

Consult your OEM owner’s manual for a table that lists tolerable levels of sulfates, chlorides, iron, and other impurities – and the pH value (acidity) – of approved water. Then, either buy distilled water that passes all the tests, or have your tap water tested through a dealer or laboratory so you know it’s OK to use. Many brands of antifreeze come pre-mixed with pure water, which solves this problem.

Don’t use too much antifreeze. The ideal mix is 50/50. If you need to go beyond that, use only as much antifreeze as you need for freeze protection, observing OEM recommendations for the maximum percentage. Remember that while a good mix cools well, antifreeze by itself won’t cool the engine properly.

The chance of mixing the wrong proportions of water and glycol is another reason to just buy pre-mixed.

What kind of antifreeze?
The two basic types of antifreeze used in heavy diesels are ethylene-glycol and propylene-glycol. David Strauss, an instructor at the North American Institute for Mack and Volvo, says the latter is sometimes used where coolants heat trailers that carry food products, as it is less poisonous, and more environmentally compatible in case of spills. Some manufacturers (like Volvo) prohibit the use of propylene-glycol, while others, like Caterpillar, limit its use to a 50/50 maximum because it does not cool as well as ethylene-glycol.

You must use a “low silicate” antifreeze approved for use in heavy-duty diesels. Coolant meeting ASTM 4985 standards is okay for most manufacturers, as it has nothing destructive in it, but you will need to add SCAs. The smart thing to do is to use a “fully-formulated” coolant that meets the TMC RP-329 standard (for propylene-glycol, the designation is TMC RP-330). Some manufacturers, like Detroit Diesel, only recommend the use of fully-formulated coolant. Since choosing fully-formulated as your initial fill gets you started on the right foot, and, when used to top the system off normally leaves it perfectly balanced, there’s usually little reason to consider using anything else.

An unprotected cooling system can allow scale to form on the outside of the liner. By holding heat in, the scale can cause the lube oil to get too hot and thin out. The result can be damage to the piston, rings and liner that looks like a lubrication failure.

What happens?
A couple of things happen to coolant as it ages. First, the additives gradually deplete as they break down in the act of protecting the metal parts of the cooling system. Second, small amounts of coolant normally leak out of the system and are replaced. The question is: With what? The biggest problem of cooling system management is controlling what goes back in.

Every driver should know what kind of coolant is in his engine, and he should replace only with the same kind. It’s ideal for the driver to carry the right replacement coolant, pre-mixed with approved water, along with him.

Coolant concentration may also change slightly because some types of coolant hoses will let water out but retain glycols. Too much glycol or too much water can easily be corrected with approved water or concentrated (rather than pre-mixed) coolant.

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