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So recently i started having problems with the thermostat on my 05 Chrysler 300. When i started looking around at how to change the thermostat there wasn't really much available and it looked somewhat more complex than changing your average thermostat. After i replaced the thermostat 3 times and having problems with the car not heating up all 3 times i figured id dig deeper into it and finally found my problem so i figured that id do a write up on how exactly to change the thermostat the easy way without removing anything but the thermostat housing with more details than the other write ups Ive found.

So to start off here are the tools that you're going to need. These tools are actually very specific and make the job about 1000x easier. The first time i did the thermostat change it took me forever using every combination of tools i could find from wobble sockets to 4 feet of extensions and this tool combination ended up being by far the easiest.
  • Flat head screw driver
  • 1/4in drive ratchet
  • 4in 1/4in drive extension
  • 1 11/16in 10mm 1/4in drive socket
Dagger Tool accessory

The length of the 10mm socket is very important to making the thermostat easier to get off. With a longer socket you cant fit it in to get to the bottom bolt. With a shorter socket and longer extension you cant very well fit a ratchet in. I started out with a regular 1/4in drive deep well socket from lowes and cut it down to the size i needed then took a round file and filed down the inside corners of the socket to get the extra burrs out. If you cant bare the $3 a replacement socket will cost, you can fight to get the housing out using wobble sockets or you can take the long route and pull the bolts out of the ac compressor and pull it out of your way but if you value your time, spend the $3 and cut the [email protected]* socket!

Alright now that you've got the tools for the job we car start in working on it. So looking at the top of your motor right here is where your thermostat housing and thermostat are located. (Under the air intake)
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The first step of the process to changing the thermostat is to drain the coolant out of your system. Now there are multiple ways of doing this. Some people will tell you to pull the front plastic skid plate off and drain the radiator from the petcock on the passenger side of the radiator but i think this is going a little bit out of the way. Now if you look at your thermostat housing you'll see a metal line that runs off the bottom of it and a rubber line that connects to the oil cooler.
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The way i like to drain the system is to pull off this rubber hose and let it drain into a pan, and since this is now becoming lower than the thermostat housing you can actually save some coolant in the radiator while draining enough that you don't make a mess when you finally get the thermostat housing off. Having the engine coolant warm when you go to pull the hose off the housing helps the hose come off quite a bit easier.

*NOTE* Now is a good time to do a coolant flush if you haven't already.

Now that the coolant is drained you can remove the devils ring, as i like to call them, and pull the hose off the thermostat housing. You can see what im calling the devils ring behind the hose clamp still on my radiator hose. I like to replace these on all of my vehicles whenever i come across them just so i never have to deal with them again.
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Now that you have that off you can begin loosening the two bolts that hold the thermostat housing into place. Looking from the top you'll be able to see the top one that is beside your exhaust manifold but you'll have to use your hand to reach down the left side of the thermostat housing to feel the other one. I like to start with the one on the left side of the housing since it is a little more difficult to get off and you can get it off easier if you aren't fighting to hold the thermostat back from removing the other bolt first. The housing is simply held on by the two 10mm bolts and to remove them both i use the ratchet, extension and the custom 10mm socket we made earlier.

When you are buying the thermostat make sure to get the gasket to go with it as it is common on these engines for the gasket to break and cause your thermostat to stick open. The gasket is kind of costly at $7 but you NEED to buy it.

Now that you have both bolts removed from the housing, remove the thermostat and gasket from the housing by pulling the housing back to the right and wiggling the thermostat out. Now that the thermostat and gasket are out you can remove the housing by turning the housing to the left as you pull up on it. Looking at your thermostat housing you will see what many of the other guides will refer to as "the factory thermostat is stacked in the housing". This is the little piece of metal in the housing as seen here.
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This is what caused me so many problems when changing the thermostat on my car since i could nowhere find what they meant by the thermostat is stacked from the factory. What this means is that you need to have the thermostat aligned just right in the housing (little notch in the thermostat aligned with notch in housing) or else your thermostat will not come close to sealing and your car will thus not warm up. Some people say you can remove this with a grinder or you can do like i did and place a little super glue around the mating surfaces of the housing and the thermostat to keep them from sliding around when you install them.

The following picture shows the alignment and placement of the gasket on the thermostat housing.
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Now all you need to do is reinstall everything working in reverse order, fill the car with coolant and bleed the system. To bleed the system i like to fill the car with coolant with the bleeder on top of the engine block open. Then once the coolant reaches the fill line in the reservoir and there is coolant coming out of the bleeder, close the bleeder and cap off the reservoir and start the car and crack open the bleeder valve a few times to get the air out.

Hopes this helps and saves someone the time that it took me to figure out!
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