When the engine is idling during warm-up, observe the following conditions:
- Check for fluid or air leaks at idle rpm and at one-half full rpm (no load on the engine) before operating the engine under load. Operating the engine at idle and at one-half full rpm with no load is not possible in some applications.
- Operate the engine at low idle until all systems achieve operating temperatures. Check all gauges during the warm-up period.
Note: Gauge readings should be observed and the data should be recorded frequently while the engine is operating. Comparing the data over time will help to determine normal readings for each gauge. Comparing data over time will also help detect abnormal operating developments. Significant changes in the readings should be investigated.
Extended Idle at Cold Ambient Temperature
The engine may automatically change speeds when the engine is idling in cold ambient temperatures (typically less than 0° C (32° F) for extended periods. The purpose of the automatic speed change is twofold: to maintain the desired operation of the NOx reduction system and to keep the engine coolant warm. The engine speed may rise to 1600 rpm for as long as 20 minutes.