Idling the Engine

The common belief that idling a diesel engine causes no engine damage is wrong. Idling produces sulfuric acid, which is absorbed by the lubricating oil and eats into bearings, rings, valve stems and engine surfaces. During long engine idling periods, the engine coolant temperature may fall below the normal operating range. The incomplete combustion of fuel in a cold engine will cause crankcase oil dilution, formation of lacquer or gummy deposits on the valves, pistons, and rings, and rapid accumulation of sludge in the engine. If the operator must idle the engine for cab heat or cooling, the high idle function of the cruise control switches should be used. For more information on high idle using the cruise control switches, Detroit Diesel Electronic Control System Features. An idle speed of 900 rpm should be enough to provide cab heat in above 0°C (32°F) temperatures. Never allow the engine to idle for more than 30 minutes. When prolonged idling is necessary, maintain an engine speed of 900 rpm.