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SERIES 638 COOLANT

The coolant provides a medium for heat transfer and controls the internal temperature of the engine during operation. In an engine having proper coolant flow, some of the heat of combustion is conveyed through the cylinder walls and the cylinder head into the coolant. Without adequate coolant, normal heat transfer cannot take place within the engine, and engine temperature rapidly rises. Therefore, coolant must be carefully selected and properly maintained. ‪

The following terms are used throughout this section and must be understood. ‪

  • Coolant - The fluid (non-diluted) Inhibited Ethylene Glycol meeting applicable light-duty formulation specifications.
  • IPG - Full strength (non-diluted) Inhibited Propylene Glycol meeting applicable heavy-duty formulation specifications.
  • Initial Fill - Any time the cooling system is empty, the filled with new coolant.
  • Dropout - Sludge or deposit formation in or on cooling system components.

Using a coolant with the appropriate concentrations of SCA is one of the most important aspects of quality engine maintenance. To achieve the chemical balance needed to protect a cooling system, certain coolant basics must be understood. ‪

This section provides the directions and information required to ensure cooling system protection. These recommendations are general rules and reflect the current technology. Specific concerns not covered should be addressed to your local Detroit Diesel representative. ‪

Water is the best practical medium for heat transfer. However, water alone can cause corrosion and inherently contains minerals that can produce scale deposits on internal cooling system surfaces. Chlorides, sulfates, magnesium, and calcium dissolved in the water can cause scale deposits, sludge deposits and/or corrosion. ‪

  • Provide an adequate heat transfer medium.
  • Provide a corrosion/erosion-resistant environment.
  • Prevent formation of scale or sludge deposits.
  • Be compatible with cooling system hose and seal materials.
  • Provide adequate freeze protection.

A properly maintained coolant can be used for two years and for unlimited mileage, whichever comes first. At this time the cooling system must be drained, thoroughly cleaned and filled with new coolant. ‪

To achieve these requirements, coolants are mixtures of good quality water, and often an IEG or IPG for freeze protection. The following pages will describe the requirements and usage of the water, IEG, and IPG. ‪

Water

Water is the best practical medium for heat transfer. However, water alone can cause corrosion and inherently contains minerals that can produce scale deposits on internal cooling system surfaces. Chlorides, sulfates, magnesium, and calcium dissolved in the water can cause scale deposits, sludge deposits and/or corrosion. ‪

Distilled or deionized water is preferred to minimize the adverse effects of minerals in water. The maximum allowable limits for minerals in water are listed in Table . The procedure for evaluating the quality of water is shown in the next illustration. See Figure 20868 . ‪

Mineral ‪

Limit - ppm ‪

Limit - grains per gallon ‪

Chlorides ‪

40 ‪

2.5 ‪

Sulfates ‪

100 ‪

5.8 ‪

Total dissolved solids ‪

340 ‪

20 ‪

Total Hardness: Magnesium & Calcium ‪

170 ‪

10 ‪

Maximum Allowable Limits for Minerals in Water

Water Evaluation Procedure

Antifreeze, Inhibited Ethylene Glycol

Ethylene glycol is used for freeze protection of the coolant. IEG, commonly referred to as "antifreeze", also contains chemicals that provide a limited protection against corrosion. The use of an IEG product with a low silicate formulation that meets ASTM D 3306 or GM 6043M requirements is recommended. ‪

Coolant Recommendation

For best overall performance, Detroit Diesel recommends a 50% concentration of IEG (1/2 IEG, 1/2 water) be used for the Turbotronic 638 engine. ‪

Coolants Not Recommended

Methyl alcohol-based antifreeze should not be used because of its affect on the non-metallic components of the cooling system and its low boiling point. Similarly, methoxy propanol-based antifreeze should not be used because it is not compatible with fluoroelastomer seals found in the cooling system. Glycol-based coolants formulated for heating/ventilation/air conditioning (HVAC) should not be used. These coolants generally contain high levels of phosphates, which can deposit on hot internal engine surfaces and reduce heat transfer. ‪

Soluble Oils

Soluble oil additives are not approved for use in the cooling systems. A small amount of oil adversely affects heat transfer. A 1.25% concentration of soluble oil increases the fire deck temperature 6%. A 2.50% concentration increases the firedeck temperature 15%. ‪

Chromate

Chromate additives are not approved for use in cooling systems. Chromate additives can form chromium hydroxide, commonly called green slime. This, in turn, can result in engine damage due to poor heat transfer. Cooling systems operated with chromate-inhibited coolant must be chemically cleaned with Nalco 2015 cooling system cleaner and conditioner (or equivalent sulfamic acid/sodium carbonate cleaner) and flushed. ‪

Some coolant filter elements with magnesium internal support plates have caused engine damage. The coolant dissolves the magnesium and deposits it on the hot zones of the engine where heat transfer is most critical. The use of elements with these plates is not approved. ‪

Summary of Coolant Recommendations

Coolant recommendations may be summarized as follows: ‪

Note: Propylene glycol meeting ASTM D 3306 or GM 6043M is approved for use.

  1. Always maintain the engine coolant to meet Detroit Diesel specifications.
  2. Only use water that meets Detroit Diesel specifications. Distilled or deionized water is preferred.
  3. Pre-mix coolant makeup solutions at the proper concentration before adding to the coolant system.
  4. Where antifreeze/boil over protection is required, use only ethylene glycol coolant (low silicate formulation) meeting ASTM D 3306 or GM 6043M.
  5. Always maintain proper coolant level.
  6. A properly maintained cooling system can be operated for up to two years, 200,000 miles (320,000 km), whichever comes first. At this interval the cooling system must be thoroughly cleaned and the coolant replaced.
  7. Do not use the following in Detroit Diesel engine cooling systems:
    • Soluble oil
    • Chromate SCA
    • Methoxy propanol-base coolant
    • Methyl alcohol-base coolant
    • Sealer additives or coolant containing sealer additives
    • HVAC coolant