This article is a reprint of an earlier article which was in Engines News, January 18, 1978.
According to field reports, some customers have had problems with damage to engine valve components during operation in very cold temperature conditions. These problems are the result of engine operation for short intervals, where the engine is started and stopped many times but does not run long enough to become completely warm.
During the interval of time that the engine operates at temperatures below normal, fuel and oil are not completely burned in the combustion chambers. This fuel and oil causes soft carbon deposits on the valve stems. Generally, these deposits do not cause problems because they are burned off during operation at normal engine temperatures. When the engine is started and stopped at short intervals, and the engine temperature is never up to normal, the carbon deposits become thicker until they prevent free operation of the valves. This can cause burnt valves, bent push rods, or other damage to valve components.
For this reason, any time the engine is started, the recommendation is to run the engine until the coolant temperature is 66°C (150°F) or higher. This will keep carbon deposits on the valve stems at a minimum.
In addition, operation of the engine until it is thoroughly warm will keep the other engine parts in better condition and generally extend the service life of the engine. Lubrication will be improved, with less acid and sludge in the oil. This will give longer service life for engine bearings, piston rings, and other parts.