Automotive thermostats are usually found in one of two different locations. The most common location is inside of the intake manifold atop the engine. This is the easiest location to access, since draining the radiator fluid is not a requirement to change the thermostat. The second location is on the lower half of the engine block. Although this location is considered to be slightly more difficult because radiator fluid must be drained, it does not require removal of engine accessories on the 1999 Chrysler 300M.
Drive the Chrysler 300M onto a set of ramps to raise the front of the vehicle off the ground. Raise it high enough so you can work under it comfortably.
Place a drain pan capable of holding four gallons of fluid under the lower radiator hose. Use a screwdriver to loosen the band clamp that secures the hose to the radiator, and then pull the hose off the radiator. Drain all of the fluid into the drain pan. This avoids loosening the petcock drain on the bottom of the radiator. Due to its age, it could be brittle.
Remove the other end of the hose from the water intake tube in the same manner as you removed it from the radiator. The intake tube holds the thermostat into the engine.
Remove the two bolts that secure the intake tube to the engine with an adjustable wrench. With the bolts removed, the intake tube, gasket and thermostat drop out of the engine. Catch them in your hand to prevent damage to the intake tube.
Remove the O-Ring, gasket and thermostat from the intake tube. Replace these older items with new ones.
Hold the intake tube against the engine and bolt it in place.
Inspect the old radiator hose for any cracks, dry rot or bubbles. If any exist, use a new hose. Slide the hose onto the water intake tube and secure it with the clamp. Place the other end of the hose back on the radiator and secure it with the clamp.
Open the radiator filler cap and drain the radiator fluid back into the radiator. If you use new fluid, use a 50/50 mix of radiator fluid and distilled water. Close the cap once filled.
