Tips for Enhancing Cold-Weather Reliability

Diesel Engines – What is Effected

Winter is here, below is a checklist of items for which bus fleet operators need to be proactive to prepare their vehicles for extreme conditions. These procedures, ranging from cooling system maintenance, to fuel choice, to selecting the right engine oil, will help your customers keep their buses running safely and reliably in cooler ambient temperatures.
 Coolant Yes Yes Yes Yes
 Fuel Yes Yes
 DEF Yes Yes
 Air Yes Yes
 Batteries Yes
 Oil Yes
  • Verify that all coolant lines and connections are leak-free.
  • Use the proper coolant/antifreeze mixture (ethylene glycol concentration) for route conditions/temperatures. A 50/50 mixture of ethylene glycol and water lowers the freezing point down to about -34°F. If you operate in temperatures colder than this, a 60/40 mixture will reduce the freezing point to about -64°F. Be sure to consult the Owners Manual that came with your vehicle. Always ensure that after any maintenance event, proper filling procedures are followed, and that the cooling system is purged of any air to protect the Exhaust Gas Recirculation (EGR) cooler.
  • Add starting aids such as a coolant heater/intake manifold heater and/or oil heater wherever temperatures typically drop below 11°F (-12°C).
  • Use winterized diesel, or blend #1 and #2 fuels.
  • Add a fuel warmer to the fuel system.
  • Double-check Diesel Exhaust Fluid (DEF) warming lines before temperatures drop.
  • Modify the air intake in extreme cold (-25°F and below) to a position adjacent to the exhaust manifold.
  • Check the cold-cranking capacity of the battery. Add a battery warmer in extreme cold conditions.
  • Customers with diesel-powered engines should switch to 5W-30 engine oil for normal winter conditions. When temperatures go below 5°F (-15°C), operators may need to consider switching from 15W-40 oil to a 10W-30 or lighter oil. They should consider switching to 0W-30 when encountering prolonged arctic cold conditions. The oil selected must meet Cummins CES 20081 specifications for diesel engines.
  • Use a dipstick oil heater to help maintain oil lubricity and improve the engine’s cold-starting capability.
  • Closely monitor and drain the water/fuel separator by opening the petcock valve and releasing any water that has accumulated in the fuel filter/separator. It is especially critical that operators perform this function when buses are running on biodiesel. Biodiesel suspends a higher amount of water than diesel fuel, has a different additive package and may require more frequent fuel-filter changes than normal. For natural gas buses, ensure that the fuel filter is checked/drained daily to prevent oil and/or heavy hydrocarbons from collecting in the filter.
  • In below-freezing conditions in which an engine typically idles for more than 15 minutes, adjust the “Fast Idle” setting to 1000 rpm to 1200 rpm. A normal idle setting of 700 rpm to 800 rpm may not provide enough heat for regeneration events. Bus operators should use the “Fast Idle” switch on the dash. Refer to your Original Equipment Manufacturer (OEM) operations manual to learn how to set up engine speeds for fast idle. When prolonged idling is required, make sure the RPM is adequate to heat the coolant above 140°F (60°C).
  • If needed, add a full on/off-type fan to aid in maintaining optimal operating temperatures.
  • Insulate exposed lines, filters, pumps and reservoirs.
  • Add a winter front for conditions below freezing.
  • If operating regularly in conditions under 32°F (0°C), pull air from within the engine compartment. Under -2°F (-19°C), pull intake air from a compartment around the exhaust stack to preheat the air.

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