The Characterization of Used Heavy Duty Engine Coolant

The demands on coolant for heavy duty engines are different from those for coolant for automotive engine and other light duty applications. The heavy duty engine coolant often runs 16 to 32,000 km/month (10 to 20,000 miles/month) at engine loads of 70%. Under these conditions the engine coolant's inhibitor package is stressed. The heavy duty engine manufacturers currently recommend the use of supplemental coolant additives (SCA) to extend engine coolant life and to provide liner pitting and hot surface scaling protection. Care must be taken to ensure that the correct SCA levels are maintained.

A survey was conducted to characterize engine coolant chemistry for a fleet of heavy duty vehicles. Analyses of the coolant, coolant filter, SCA, make-up coolant and water showed many variables are involved in maintaining the correct balance of inhibitors in the cooling system. The information presented in this paper should help the fleet owner and operator in reviewing/ planning maintenance practices and disposal or recycling options.