The May issue of Construction Equipment has an article about maintaining diesel-engine coolant, but with a bit of a twist compared with coolant articles we’ve published in the past. We asked three coolant specialists to address a list of questions about maintaining coolant in diesels and about existing and new antifreeze formulations. They disagree just enough to make things interesting.
We’re not going to give anything away about the article at this point, but would like to share a few items of interest that ended up, so to speak, on the editing floor—because there’s only so much space in the magazine.
For example, in the article, we just briefly touch on the benefits of coolant analysis, which, like oil analysis, is a practical way to monitor coolant condition over time. And also like oil analysis, coolant analysis can reveal potential problems with a diesel early enough to avert possible disaster.
For instance, did you know that stray electric current in a vehicle can find its way into a diesel’s cooling system if the cooling system represents the path of least resistance to ground?
We heard from a coolant-analysis lab about an over-the-road class-8 truck that developed an electrical short in its starter. During a cross-country run, the stray current depleted the nitrite additive in the truck’s fully formulated coolant, resulting in a ruined engine. With no nitrite to fight the process of cavitation, the engine’s wet cylinder liners were so severely eroded that coolant entered the combustion chambers.
Cavitation is the process of vapor bubbles imploding with terrific force against the coolant side of the liners as the liners vibrate with the diesel’s combustion cycle. Nitrite forms an anti-cavitation barrier on the liner, but if there’s no nitrite, there’s no protection.
When a coolant analysis lab sees nitrite levels dropping, accompanied with an increase in nitrates, then electric current passing through the cooling system is a prime suspect. If you discover this in time, you could potentially save an engine. The preventive-maintenance side of the story is to make sure that electrical accessories you add to your truck or construction machine are properly grounded.
If the report on a coolant sample, which maybe you sent in with the routine oil sample, comes back indicating a sharp drop in pH (usually below 7) and accompanied by an increase in sulfates, then a combustion-gas leak might be causing the problem. Catching a bad head gasket early enough could save you a ton of money.
Or, if the coolant system has an air leak, pH might again drop (but usually not below 7.5) and nitrite will be diminished, but not as rapidly as with an electrical short.
And, of course, coolant analysis turns up more mundane conditions as well, such as improper freeze point; contamination by mixing antifreeze types; the presence of solids (perhaps the result of overdosing with an additive package); the presence of corrosion (the natural tendency of metals to revert to their ore form); and hard-water scale, which impedes the diesel’s ability to transfer heat. As heat increases in the cooling system, hardness salts, such as calcium and magnesium in solution, have a tendency to plate out on hot metal.
Coolant analysis is not an important maintenance practice in most fleets, but the benefits of making it so seem compelling.