The thermostat blocks the coolant from flowing right into the radiator together the engine is warming. A fault with the thermostat can reason reduced engine performance and also overheating, typically seen ~ above the tool gauge panel.

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This article applies to the dodge Ram 3rd Generation (2002-2008).

Thermostats control engine temperature through opening and closing the i to the radiator. Once the engine is an initial started, it requirements to warm as rapid as possible. Keeping coolant from reaching the radiator accelerates this process, reducing wear and emissions. Thermostats use both seals and also springs to move as well as block coolant flow. No electronic devices are provided to do the thermostat operate. Instead, a wax pellet that melts when the coolant will a particular temperature paint, etc the thermostat closed.

Thermostats can become stuck open up or closed. A grounding closed thermostat will cause the engine to operation cooler 보다 normal, while a stuck open thermostat can reason the engine to overheat really quickly.


Materials NeededSocket collection (10mm-18mm)Ratchet (1/2" or 3/8")3" ratchet extensionFlat head screwdriverThermostat3-4 gallons of coolant (buy HOAT (Mopar) coolant because that trucks through it already installed)Drain pan3/4" wrench

The place of the thermostat for the 5.7 hem engine and also the 4.7/3.7 engines are different. On the Hemi, the thermostat is located on the engine at the upper radiator hose below the A/C compressor. The 4/7 and also 3.7 engine"s thermostat is located on the reduced radiator hose near the harmonic balancer.

Step 1 – drainpipe the coolant from the radiator

Remove the radiator cap by pushing it down, and also then twisting the counterclockwise.

At the driver"s next bottom corner of the radiator is a drainpipe blocked through a plug. Revolve this plug counterclockwise with a 3/4" wrench ~ you location a drain pan in ~ it.

Figure 1. The radiator drain plug.

Step 2 – remove the thermostat

To reach the thermostat, you need to remove the hose neck native the engine. 2 bolts organize it in place. As soon as it"s removed, the thermostat will slide out.

Figure 2. The red circle shows the position of the water tap filler neck on the 5.7 engine.
Figure 3. A diagram of the 5.7 thermostat. Number 1 shows the water tap filler neck bolts. Number 2 indicates the filler neck.
Figure 4. The thermostat place on the 4.7 and 3.7 engines. You deserve to see the harmonic balancer in ~ the reduced right next of the image.
Figure 5. A diagram of the thermostat on the 4.7 and also 3.7 engines.

Step 3 – install the new thermostat

Some thermostats come through an waiting bleed valve and notch at the sheet of the diaphragm. The notch have to be filed right into the brand-new thermostat to look favor the factory thermostat for suitable fitment with the O-ring. The bleed valve is not required; although, that does do bleeding the cooling device of air easier. Transfer any kind of gaskets from the original thermostat not found on the brand-new thermostat if they space in great condition; otherwise, girlfriend will should buy new ones. Make sure they room orientated effectively for suitable fitment into the block and hose filler neck. The spring side the the thermostat will certainly be dealing with the engine.

Bolt the hose filler neck back onto the engine through the thermostat correctly inserted inside.

Figure 6. You deserve to see the bleed valve ~ above the face of the initial thermostat ~ above the left. Both thermostats have the notch ~ above the edge.
Figure 7. The red arrow points come the slot in the hose filler neck that fits to the thermostat O-ring.

Step 4 – Fill and bleed the cooling system

You will certainly need around three gallons that 50/50 mixed coolant to fill the cooling system. Because that trucks utilizing HOAT coolant, be sure to use the exact same type. For the 4.7 and 3.7 engines, remove the upper radiator hose and fill the engine with as much coolant as possible.

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The remainder of the instructions use to every engines. To fill the radiator, and then fill the coolant restore tank come the cold full mark. Leave just the restore tank"s lid off. Currently start the engine and turn the heat to the max setting. It will take number of minutes because that the cooling mechanism to warm and move air with the system. Once the temperature gauge reaches around 1/4 that the method to the half mark, shut the engine off. Peak off the coolant in the restore tank together needed throughout this procedure. Put the recovery tank cap ago on and start the engine again. If the temp gauge rises above halfway, you might still have air in the system and will must repeat the bleeding procedure when the engine is cool sufficient to do so.