Maintaining Heavy Duty Truck Cooling Systems

The coolant in a heavy duty diesel works harder than the coolant in any other engine. It operates at higher temperatures, is pumped at higher velocities, and has to protect more types of components for longer periods than in any other application. Of course it'd different!

40% of Heavy Duty Engine problems are traced to poor coolant system maintenance.

ASTM established an important coolant performance specification in ASTM D6210, and its sister ASTM D6211. D6210 defines the requirements for ethylene glycol based heavy duty fully formulated antifreeze / coolants, virgin or recycled, and D6211 does the same for propylene glycol based products.

This page cannot cover all of the requirements of heavy duty diesel engines. An overview will be offered

Conventional Chemistry:

Heavy duty conventional chemistries are marketed by engine manufacturers. They are fully formulated, and are also the dominant factory-fill fluids at truck and bus manufacturers. Caterpillar DEAC, Detroit PowerCool, and Fleetguard Compleat are the mainstay products. These products need to be maintained with supplemental coolant additives. Maintenance is performed either through changing charged coolant filters, or by adding liquid SCAs. It has been customary to add SCA's at every PM service interval, and this works well if the coolant is changed every two years.

A more sophisticated program calls for the use of extended service filters and/or test-to-add practices, permitting the coolant to remain in service for 4 or 5 years, and 500,000-750,000 miles, whichever comes first.

Carboxylate and Hybrid Chemistries:

Extended life products can provide a lower maintenance requirement, but the error of ignoring the coolant system should be avoided! Experience has shown that trucks running these coolants are frequently exposed to contamination with other coolants, and/or dilution with water. Inspection of the cooling system at every PM is important; inspection should include a freeze point check.

Depending on the type of coolant and the engine manufacturer, the coolant will require an additive, designed for the technology in use, at 150,000 to 300,000 mile intervals. The coolant will be able to serve to about 600,000 miles if maintained properly.

Recycled Coolants for HD Diesels:

Recycled coolants for heavy duty diesels must meet the same specifications as new coolants. Filtration recycling is not an option in heavy duty truck systems