Usage:
3406, 3408 Truck Engines
It is important to maintain the correct engine temperatures during cold weather. Operation at low engine temperatures will cause increased fuel consumption and increased engine component wear. The articles that follow were printed in earlier Service Magazines. They are reprinted here as a reminder of possible corrections to the problem of overcooling.
Valve Damage Can Be Caused By Short Intervals Of Engine Operation In Cold Temperatures
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.
Low Engine Temperatures: Install Check Valve
Operation of 3406 and 3408 Truck Engines at below normal engine temperatures can cause increased fuel consumption and increased engine component wear.
Engine operation at temperatures below 71°C (160°F) is usually found when heater performance is not correct and/or the temperature gauge indication is low.
Check the engine operation temperatures with a gauge of known accuracy. This will give a check of the truck's engine temperature gauge.
The main cause of low engine temperatures is the flow of coolant past the water temperature regulators at a temperature below 71 °C (160°F). Identification of the leakage circuit is necessary to correct the problem. To do this, check:
1. Operation of the water temperature regulator.
2. Make sure the correct regulator cover assembly is used. Use of the wrong cover assembly can cause low engine temperatures. See the article that follows.
If the water temperature regulator works correctly and the correct regulator cover assembly is used, an 8N9071 Valve Assembly can be installed in the air vent line. The air vent line, which goes from the cylinder head to the radiator, is used to remove air from the engine cooling system. Without the check valve, it is possible for coolant to flow through the air vent line when the water temperature regulator is closed. The check valve prevents this coolant flow.
Inspect Regulator Cover Assembly When Overcooling Is A Problem
In the 3400 Series Engines, one of two designs of regulator cover assemblies is used, according to the type and serial number of the engine. Early 3406 (92U3134 and earlier) Truck Engines use a 4N362 Regulator Cover Assembly. This regulator cover has a small hole near the opening for the water temperature regulator. A ferrule is installed in this hole. The ferrule has an orifice to vent (let out) air vapor from the engine. Loss of this ferrule will cause overcooling, so inspect the cover to make sure the 2H1193 Ferrule is installed as shown.
The 3408 and later 3406 Truck Engines have a 9N947 Regulator Cover Assembly. This regulator cover does not have a vent hole, and a separate line is used to vent vapor from the engine. If a wrong cover (with a vent hole) has been installed, it will cause overcooling.
Location of 2H1193 Ferrule on the 4N362 Regulator Cover Assembly.