The Dodge Neon is a pretty simple and basic car. Repairing the Neon is pretty simple, too, even for the amateur home mechanic. Although many engine components are difficult to reach due to the small amount of space in the engine bay, the thermostat is right up front, on the passenger's side of the engine bay. Replacing it takes about an hour and a half, if you follow the procedure and have the correct tools. Although the Neon received a redesign in 2000, these steps are applicable to all models produced between 1994 and 2005 (the last year) with the 2.0L engine.
Let the Neon's engine cool down for about 30 minutes, and then unhook the negative (black) battery cable.
Position a drain pan or container underneath the passenger side of the radiator. Examine underneath to find the radiator drain plug. Remove the drain plug to let the engine coolant drain into the pan. This process will take 20 to 30 minutes.
Unhook the coolant reservoir hose from the thermostat housing (passenger side of engine bay). Let the hose drain into the pan to avoid spilling any leftover coolant on the ground.
Use the pliers to remove the hose clamp from the upper radiator hose (where it connects to the thermostat). Pull the hose away from the housing. Let the hose drain into the pan.
Spray the two thermostat housing mounting bolts with a solvent, such as Liquid Wrench or PB Busters. Let the solvent sit for about 15 minutes before removing the bolts.
Remove the two bolts. You'll need a socket extension to reach the bottom bolt. Once the bolts are removed, pull the housing off.
Pull out the thermostat, and then pull off the thermostat o-ring. The o-ring may be damaged and hard to remove. Carefully scrape it off with a flat-head screwdriver.
Wipe down the mounting surface with a dry shop towel. Make sure the mount is clean before installing the new thermostat and o-ring.
Insert the new o-ring, and then attach the new thermostat. Pay attention to the position of the thermostat. The small valve should be facing up. Attach the thermostat housing and tighten the bolts to 9.2 foot-lbs. of torque.
Reattach the radiator hose and tighten the clamp. Attach the coolant reservoir hose. Replace the radiator drain plug and refill the cooling system.
Reconnect the negative battery cable and start the engine. Inspect the hoses and look underneath the car for leaks.
