The thermostat blocks the coolant from flowing into the radiator as the engine is warming. A fault v the thermostat can reason reduced engine performance and also overheating, frequently seen on the instrument gauge panel.

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This article applies to the evade Ram third Generation (2002-2008).

Thermostats regulate engine temperature by opening and also closing the passage to the radiator. When the engine is first started, it needs to warm as rapid as possible. Maintaining coolant from reaching the radiator accelerates this process, reducing wear and emissions. Thermostats usage both seals and springs come move and block coolant flow. No electronic devices are provided to make the thermostat operate. Instead, a wax pellet the melts when the coolant get a certain temperature color etc the thermostat closed.

Thermostats can become stuck open up or closed. A grounding closed thermostat will reason the engine to run cooler than normal, while a stuck open up thermostat can reason the engine come overheat an extremely quickly.


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

The ar of the thermostat for the 5.7 hemi engine and also the 4.7/3.7 engines are different. ~ above the Hemi, the thermostat is situated on the engine at the top radiator hose listed below the A/C compressor. The 4/7 and also 3.7 engine"s thermostat is situated on the reduced radiator hose near the harmonic balancer.

Step 1 – drainpipe the coolant native the radiator

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

At the driver"s next bottom edge of the radiator is a drain blocked by a plug. Turn this plug counterclockwise v a 3/4" wrench after you place a drain pan in ~ it.

Figure 1. The radiator drain plug.

Step 2 – eliminate the thermostat

To reach the thermostat, you must remove the hose neck indigenous the engine. Two bolts organize it in place. Once it"s removed, the thermostat will slide out.

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

Step 3 – install the new thermostat

Some thermostats come v an wait bleed valve and also notch in ~ the edge of the diaphragm. The notch must be filed right into the brand-new thermostat come look choose the factory thermostat for appropriate fitment v the O-ring. The bleed valve is not required; although, the does do bleeding the cooling device of wait easier. Transfer any kind of gaskets native the original thermostat not found on the new thermostat if they space in an excellent condition; otherwise, you will need to buy brand-new ones. Make sure they space orientated effectively for appropriate fitment right into the block and also hose filler neck. The feather side that the thermostat will certainly be dealing with the engine.

Bolt the water tap filler neck back onto the engine v the thermostat correctly inserted inside.

Figure 6. You deserve to see the bleed valve top top the challenge of the original thermostat ~ above the left. Both thermostats have the notch on the edge.
Figure 7. The red arrowhead points to the slot in the water tap filler neck that fits come the thermostat O-ring.

Step 4 – Fill and also bleed the cooling system

You will certainly need about three gallons the 50/50 blended coolant to fill the cooling system. Because that trucks utilizing HOAT coolant, be certain to use the very same type. Because that the 4.7 and also 3.7 engines, remove the upper radiator hose and also fill the engine through as much coolant together possible.

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The rest of the instructions use to every engines. To fill the radiator, and also then fill the coolant recovery tank come the cold full mark. Leave only the restore tank"s cap off. Now start the engine and also turn the warmth to the max setting. It will take several minutes for the cooling mechanism to warm and also move air with the system. When the temperature gauge reaches around 1/4 of the way to the half mark, closeup of the door the engine off. Optimal off the coolant in the restore tank together needed throughout this procedure. Put the restore tank cap back on and start the engine again. If the temp gauge rises over halfway, you may still have actually air in the system and will have to repeat the bleeding procedure once the engine is cool enough to execute so.