Lately we’ve been receiving a lot of questions at the service counter about idling the truck. Excessive idling of our newer equipment causes premature engine wear and causes problems in the after treatment systems.
Truck Engines manufactured today are designed to operate at higher temperatures to burn the impurities out of the combustion chambers of the engines. That is the reason your fan hub will not engage until the engine reaches between 200 and 205 degrees. While idling, your engine temperatures will never reach these levels. The higher temperatures will only be reached when driving down the road. Because idling will never get to a high enough temperature, impurities will clog up the DPF “Diesel Particulate Filters”. This results in premature cleaning and baking the filters out – and the cost can be sizable.
To further expand on this idea, here are some Q&A responses with Mac Patterson, an expert in diesel engineering and development:
First, one must understand the physics of idle, what is happening internally in the engine. When an engine is operating at full power the pressure on top of the cylinders runs about 1500 lb per square inch - at idle this is reduced to about 550 lbs.
At full power, some of this pressure is routed by the top of the piston and gets behind the top ring, holding a firm seal between the combustion chamber and the crankcase. This prevents the combustion gasses, which are full of undesirable compounds (i.e. Sulphur, Carbon, etc.), to enter the crankcase.
At idle, the rings are relaxed and are not properly sealing, this is the reason you will not see blowby on a healthy engine at full power, only during idle will blowby be present. Sitting and idling all night one will observe black oily soot running down the outside of the stack. This same black oily soot is also running down between the piston and liners in the long-term idle mode.
The above situation allows the entry of acids, carbon, water, and other undesirable compounds into the crankcase, requiring premature oil changes, bearing etching and all kinds of problems. This added cost to engine maintenance is considerable. There is no good reason to idle a truck.
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