The F-350 designation refers to a 1-ton Ford F-Series pickup truck. The thermostat in your diesel-powered Ford closes off the flow of coolant when the engine is cold, forcing the engine to heat up faster. When the coolant has reached a certain temperature, the thermostat opens up and the coolant flows as normal. A malfunctioning thermostat in your diesel may cause your engine to overheat if the thermostat gets stuck in the closed position. Installation of a new thermostat will cure the problem and get you back on the road.
Open the hood. Allow the motor to cool off so that you will not be scalded by hot coolant. Locate the thermostat housing by tracing the upper radiator hose from the driver’s side of the radiator to its termination at the thermostat housing.
Remove the cap from the white plastic coolant bottle at the front of the engine bay. Place a drain pan under the radiator drain petcock on the lower side of the radiator on the driver’s side of the truck. Remove the petcock by rotating it counterclockwise with a 19mm wrench. Replace the petcock and tighten it in a clockwise direction once the coolant has fully drained.
Remove the clamps from both ends of the upper radiator hose with a pair of pliers. Pull the hose from the radiator and from the thermostat housing, using a twisting motion. Set the hose and clamps aside.
Spray penetrating fluid on the three mounting bolts on the thermostat housing and let it soak in for a few minutes. Remove the three bolts with an 8mm wrench turned counterclockwise. Remove the thermostat housing from the water pump and set it and the bolts aside.
Remove the thermostat housing from the water pump to reveal the thermostat. Carefully pry the thermostat up with a flat-blade screwdriver if necessary. Clean the mating surfaces on the thermostat housing and at the water pump with a rag.
Place a new thermostat into the water pump with the pointed end facing upward. Install a new O-ring gasket into the groove on the thermostat housing mating surface of the water pump. Position the thermostat housing back onto the water pump and tighten the three bolts with a torque wrench to 15 foot-lbs.
Push the upper radiator hose back onto the radiator inlet and the thermostat housing until it is fully seated at both ends. Replace the hose clamps in their original position with a pair of pliers. Refill the coolant that you drained from the radiator back into the white plastic coolant tank and replace the cap. Start the engine and let it warm up. Check for leaks and retighten your connections if necessary.
