VALVE-RELIEF 4306091 - Caterpillar

Diesel Engines With Jacket Water AftercoolingReference: Engine News, September 1992, Page 6, "Supplemental Coolant Additive Requirements" for Caterpillar diesel engines with jacket water aftercooling.The Reference Article discussed the mixture for Caterpillar engine coolants and indicated that water and supplemental coolant additive (SCA) would be acceptable for engines where freeze protection was not needed. However, the use of glycols provides benefits in addition to freeze protection.
Coolant mixtures with the glycols produce higher boiling temperature. The water and glycol coolant mixtures require less SCA because the water portion is the part requiring the SCA. Less SCA in the mixture will result in less deposits on the water pump seal faces and thus longer seal life. Less SCA in the mixture also results in less deposits on high temperature surfaces. All these factors provide overall improvement in engine operation and life.
The use of the water only coolant should be restricted to low power ratings of marine engines. Even for these applications, the positive factors (indicated in the previous paragraphs) for the use of glycols in the cooling system should be considered in the overall operating cost of the engine.
Engine applications which are now using coolant mixtures with glycol, even though freeze protection is not needed, should not decide to remove the glycol part of the coolant mixture based only on the information in the Reference Article. As previously discussed, significant additional benefits are available when using the glycol as a part of the coolant. Caterpillar has expended effort promoting the use of proper engine coolant mixtures. These efforts have and will produce positive results for customers. The long term benefits of using the proper engine coolant mixtures will greatly outweigh the short term cost saving of not using glycols in the mixture.
Therefore, the Reference Article article is not incorrect when it indicates that water and SCA can be used with the proper treatment as an engine coolant. But, field experience indicates that a water and SCA coolant mixture is NOT the most cost effective engine coolant mixture.
The continued use of coolant mixtures with glycol, water and SCA is the best approach to achieving the best overall engine operation. The proper quality of water is very important since poor quality water can immediately degrade the SCA performance and also cause deposits. The correct amount of the correct SCA is certainly important. Too much or too little SCA can be detrimental. The glycol should also be the proper formulation. The ASTM D4985 Specification defines a low SCA commercial product which can be treated with the SCA without chemical dropout with the normal treatment.