Usage:
3406 Truck Engine
Description of Change: The vent hole in the cover for the water temperature regulator has been removed. In the past, coolant flowed through the vent hole and into the radiator when the regulator was closed. This permitted too much heat loss.
To prevent air from being caught inside the engine when it is filled, it is necessary to fill the cooling system carefully. Use the procedure which follows:
1. Fill the cooling system until the coolant is at the top of the filler neck.
2. Operate the engine until the coolant temperature is above the thermostat setting.
3. Add coolant and repeat until there is no change in coolant level. When the cooling system is drained with the new cover assembly installed, loosen the hose clamp at the thermostat outlet and break the hose seal. This will release the water between the thermostat and radiator top tank. See the illustration.
Adaptable To: The new 9N947 Cover Assembly is a direct replacement for the former cover. The part number did not change. 3406 Truck Engines with Serial Numbers 92U63839-Up have the new cover assembly already installed on the water temperature regulator. Former covers for the water temperature regulator can be modified. To do this, dip a 4B4161 Drive Screw in Loctite and install it in the vent hole.
Location of new 9N947 Cover Assembly.