3116 and 3126 HEUI Truck Engines Cold Weather Operation

Caterpillar Diesel Engines can operate effectively in cold weather. However, engine starting and operation in cold weather is dependent on the type of fuel used, the oil viscosity, and other optional starting aids and warm-up aids. The purpose of this section is to:

* Explain potential problems that are caused by cold weather operation
* Suggest steps which can be taken in order to minimize starting problems and operation problems when the ambient air temperature is colder than 0°C (32°F) down to -55°C (-67°F)

NOTE: Frequent maintenance checks (more than those specified in the Maintenance Schedule) will be necessary when operating under freezing cold conditions.

A discussion of all of the factors that affect the operation and maintenance of an engine in cold weather is difficult to outline in one publication. This is because of the differences in weather conditions, engine applications, and the supplies that are available in different areas. These factors, along with recommendations from your Caterpillar dealer and past proven practices should be combined with the information in this section to provide guidelines for cold weather operation.

Cold Weather Hints

* If the engine is started for any reason, operate the engine until a minimum operating temperature of 71°C (160°F) is achieved. This will help to prevent the valves from sticking due to unburned fuel.
* The cooling system and the lubrication system of the engine do not lose heat immediately upon shutdown of the engine. This means that an engine can be shut down for a few hours and still start readily. If the engine is shut down for at least eight hours, the engine should be considered cooled to the outside temperature.
* Utilize the correct lubricant or fluid for each engine compartment before cold weather begins.
* Inspect all of the rubber parts (hoses, fan belts, etc) weekly.
* Inspect all of the electrical wiring and connections for any frays or damaged insulation. Keep all of the batteries fully charged and warm.
* To prevent condensation on exposed fuel tank walls, fill the fuel tank when the engine will be shut off for eight hours or more. Keep the fuel tank as full as possible.
* Inspect the air cleaners and the air inlet daily, or as necessary, when working in snow.
* Inject starting fluid only when the engine is cranking.
* Air system dryers may be effective in reducing condensation and ice formation in air systems.
* Alcohol injection may prevent moisture from freezing the air compressor regulator and other components of the air system.
* For jump starting with cables in cold weather, refer to the topic in this manual.

Fuel Recommendations for Cold Weather

The three types of diesel fuel available for your vehicle engine are typically grades No. 1, No.2 or a blend of No. 1 and No.2.

There are three major differences between No. 1 and No.2 diesel fu fuel. No. 1 diesel fuel has a lower cloud point, a lower pour point and has a lower kJ (Btu) (heat content) rating than No.2 diesel fuel. The kJ (Btu) rating indicates power, therefore No. 1 grade fuel will provide less power and fuel economy, but is less likely to plug the fuel filters and flows better through the fuel system. Keep in mind that No. 1 grade fuel or fuel blends will not provide as much power as No.2 grade fuel. A difference may be noticed.

Be aware of these fuel grades when purchasing your diesel fuel. Plan fuel purchases for cases of driving from warm climates into cold climates. Vehicles that are fueled in one climate may not operate satisfactorily when driven to another climate. Before troubleshooting for low power or poor performance in winter months, check the type of fuel or blend of fuel that is being used.

No.2 diesel may be blended with No. 1 or kerosene in the following proportions to achieve lower temperature flow capabilities.

Fuel Related Components

Fuel Heaters

When the use of unblended No.2 diesel in the winter cannot be avoided, a thermostatically controlled or self regulating fuel heater can be installed. Fuel heaters are not effective for cold starts unless they are powered by an external source (i.e. AC current). Select a fuel heater that is mechanically simple, yet adequate for the application. Choose a fuel heater with as large a heating surface as practical. Small fuel heaters can be too hot for their limited surface area.

NOTE: Heat exchanger type fuel heaters should have a bypass provision to prevent excessive heating of the fuel in warm weather operation. The excessive heating of the fuel will cause a loss of engine power. Consult your Caterpillar dealer for information on the fuel heaters that are available for your engine.

Disconnect or deactivate the fuel heater in warm weather in order to prevent excessive heating of fuel and possible engine power loss. A gradual loss of engine power occurs as the temperature of the fuel increases. Electronic engines will correct for higher fuel temperatures to a limit. Consult your Caterpillar engine dealer for information.

Fuel Filters

A primary fuel filter and/or water separator is installed between the fuel tank and the engine mounted fuel filter. The location of the primary fuel filter is important in cold weather operation. The primary fuel filter and the fuel supply line are commonly affected by cold fuel. The best location for the primary fuel filter is in the engine compartment, where the primary fuel filter will benefit from the radiant heat of the engine. A primary fuel filter that is mounted outside the frame rails, or in any location that is exposed to wind, can be a persistent problem in cold weather.

Engine Lubrication Oil Viscosity

Proper engine oil viscosity is essential to ensure engine starting at cold ambient temperatures. Refer to the Lubricant Viscosity chart for recommended oil viscosities to use at various operating temperature ranges.

Oil Pan Heater

Oil pan heaters are useful devices to assist in reducing the cranking amperage that is needed to start the engine. Oil pan heaters improve the flow of oil at start-up and reduce the time that is needed to warm the engine up. Oil pan heaters also increase the service life of bearings. Oil pan heaters can reduce the normal minimum ambient temperatures -20°C (-5°F) at which multi-grade API CG-4 oil can be used. Consult your vehicle dealer for more information.

Coolant Recommendations

Engine coolant should offer the correct mixture of glycol and water for the lowest minimum ambient temperature expected. Refer to the Coolant Specifications.

Check the coolant frequently in cold weather for glycol concentration in order to ensure adequate freeze protection.

Jacket Water Heater

A jacket water heater can improve the startability and reduce warm up time by heating the coolant that surrounds the combustion chambers. An electric jacket water heater can be activated as soon as the engine is stopped. Use of a jacket water heater reduces the temperature at which ether is required. An effective jacket water heater is typically a 1250/1500 W unit. Consult your vehicle dealer for more information.

Cold Weather Starting Recommendations


Batteries must provide sufficient amperage needed to start and operate the engine at the coldest expected temperatures.

Maintain the proper battery electrolyte level. Keep all batteries fully charged (to a corrected specific gravity of 1.250 or above). Keep the batteries warm. The temperature of the battery has a considerable effect on the available power. If the battery is too cold, the battery will not have enough power to crank and start the engine, even if the engine is warm. Batteries typically have only fifty percent of the capability at -10°C (14°F) versus 27°C (80°F). At -35°C (-31°F), only ten percent of the original power is available. To maximize the battery power, heat the battery compartment or store the battery in a warm location.

Inlet Air Heater/Ether Start System

As temperatures drop below 0°C (32°F), starting a cold engine requires assistance in the form of ether starting aids or inlet air heaters. An automatic metered ether injection system is preferred over a manual system. An automatic ether injection system reduces the risk of engine damage by minimizing the operator’s responsibility to correctly determine how much ether is required. Excessive ether will damage the engine and void the manufacturer’s warranty.

An alternative to ether is an inlet air heater. The preheated inlet air considerably improves the engine’s cold starting ability at very low temperatures and ensures smooth engine operation within a shorter period of time.

Engine Idling

When idling after startup in cold weather, increase the engine speed to 1000 to 1200 rpm in order to warm up the engine more quickly. Do not race the engine to speed the warm-up.

When idling, the application of a light (parasitic) load will assist in maintaining the minimum operating temperature of 71°C (160°F). The installation of a hand throttle will make it easier to maintain an elevated low idle speed for extended periods. An idle speed of 1000 rpm is preferred for all engines.

Exhaust Restrictor

Exhaust restrictors apply a load to the engine in order to reduce warm-up time and white smoke at start-up. When extended idling periods are unavoidable, the exhaust restrictor can help maintain acceptable coolant temperatures above 71°C (160°F). Exhaust restrictors for the engines can also be obtained from other companies.

Coolant Warm Up

Recommended Options

If a vehicle has been parked long enough for some of the systems to cool much below normal operating temperatures, the systems should be warmed up before returning the engine to full operation. Damage to engine valve components during operation in very cold temperature conditions can result from engine operation for short intervals. This can happen if 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 frequently (short interval trips) and the engine operating temperature is seldom or never up to normal, the carbon deposits become thicker. This will prevent free operation of the valves and can stick valves, bend push rods or result in other damage to valve train components.

For this reason, any time the engine is started, run the engine until the coolant temperature is 71°C (160°F) minimum. This will keep carbon deposits on the valve stems at a minimum and maintain free operation of the valves and valve components.

In addition, operating the engine until the engine 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 provide longer service life for the engine bearings, piston rings, and other parts. However, limit unnecessary idle time to ten minutes. Engine wear is greatest at low idle and unnecessary idling wastes fuel.

On/Off Fan Clutch

For better control of fan operation, an ON/OFF fan clutch may be used. ON/OFF fan clutches can help prevent excessive cooling in cold weather. Viscous fans often rotate continuously in cold weather. Fan clutches that keep the fan stationary in the OFF position reduce unnecessary air movement in order to help maintain adequate engine operating temperatures.

Purge Valve/Insulated Heater Lines

To help prevent excessive cooling of the engine during lightly loaded periods of operation, the coolant must be made to bypass the radiator. Coolant passing through the radiator must be minimized in order to maintain the engine operating temperature in cold weather.

Valves that allow air flow but prevent coolant flow (often called “jiggle” valves) can help prevent excessive cooling. These valves prevent unnecessary coolant flow which may divert around the water temperature regulator to the radiator.

Insulated cab heater lines for very cold climates are also beneficial. Insulated cab heater lines provide more available heat from the coolant to the cab with less heat lost to the outside air.

Air Inlet and Cab Insulation

When temperatures below -18°C (0°F) will be frequently encountered, an under-the-hood air cleaner inlet may be specified. This is sometimes referred to as a “Snow Valve”. An under-the-hood air cleaner inlet may also minimize the packing of snow into the air cleaner. Heat rejected by the engine through convection can warm the inlet air.

Additional heat can be retained around the engine by specifying additional insulation for the cab and the hood when the vehicle is ordered. This will improve the comfort level of the operator, particularly while idling overnight.

Winter Front/Shutters

With the introduction of air-to-air aftercooling, the use of winter fronts or shutters for normal operating conditions above freezing requires caution in order to avoid high inlet and exhaust temperatures. The restriction in air flow can cause higher exhaust temperatures, power loss, excessive fan usage, and a reduction in fuel economy.

However, winter fronts or shutters are useful in maintaining minimum engine coolant temperatures when the outside air temperatures drop below freezing. If the engine coolant temperature is above the minimum of 160°F (71°C), a winter front is not needed no matter how cold the ambient temperature. The water (coolant) temperature should be monitored with the dash gauges so the engine does not overheat when the winter front is used.

The following guidelines apply if a winter front or shutter is used.

* 1°C (34°F) or higher – Open or remove the winter front.
* -18 to 0°C (0 to 32°F) – Use a winter front with circular or diamond shaped opening directly in line with the fan hub. Use a minimum opening of 385 cm2 (60 inch2).
* -29 to -18°C (-20 to 0°F) – Use a winter front with an opening of 192.5 cm2 (30 inch2).
* -34 to -29°C (-30 to -20°F) – Use a winter front with opening of 102 cm2 (16 inch2). Position the opening directly in line with the fan hub.
* Below -34°C (-30°F) – Completely close the winter front.
* Overnight Idling – Completely close the winter front.

Winter fronts are generally less expensive than radiator shutters. If radiator shutters are installed, the shutter thermostat (if automatic) should open the shutters at a temperature that is 6°C (10°F) lower than the opening temperature of the engine thermostat.

The following charts were designed to assist dealers and customers equip and operate their Caterpillar diesel engine effectively in frigid weather. Starting aids should be selected that allow the engine to start at the various temperature ranges without the need for extended cranking periods. If extended idling periods are unavoidable, some or all of the idle temperature and coolant warmup devices should be considered based on the maximum temperatures expected. The goal is to maintain a minimum engine coolant temperature of 160°F (71°C).

Cold Weather Recommendation Charts

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