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Here is a DIY for replacing thermostats. This was done on an LLY truck, but I would imagine it is the same or similar across all platforms.


The thermostats are both located near the front center of the engine in between the alternator and AC compressor. Note, I removed my turbo noise suppressor, if you haven't you will need to remove that before starting. If you haven't already, drain a little bit of coolant (maybe 1 gallon). There is a drain valve on the bottom of the radiator on the passenger side. REMOVE THE SURGE TANK CAP FIRST to remove pressure from the system, then replace surge tank cap and remove drain plug. This will allow somewhat of an air-lock so the coolant will drip out instead of spray.



1. Remove the turbo noise suppressor bracket and the wires held to it.



2. Remove the 12mm bolt holding the black coolant pipe to the thermostat housing



3. Remove the four 12mm bolts in the thermostat housing.



4. Now we need to loosen the black coolant pipe so we have some play in it. First remove the 12mm bolt holding the black coolant pipe to the drivers side head.

 

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5. accessing the 2nd bolt on the coolant pipe is a PITA. First, unplug the two large engine electrical plugs. Then use a torx bit (I think a T-20) to remove the lower plug from the metal mount. Next LOOSEN but DO NOT REMOVE the bolt that is under the intercooler tube near the firewall that holds the electrical connectors to the head (see picture below)



6. Now remove the two remaining bolts holding the electrical connector bracket down.




7. With those two removed and the third loose you should be able to wiggle the bracket out of the way enought to loosen the 2nd bolt holding the coolant pipe to the head.

8. Now gently wiggle the thermostat cover loose, you may need to give it a light tap with a RUBBER hammer. I decided not to unattach the black coolant pipe from the thermostat housing, I was able to work around it. You can if you want, it's your choice. Once the thermostat housing is removed you will be able to see the thermostats.



9. Take the two old thermostats out and be sure to clean out all of the old rubber gaskets on the thermostats.

10. Install the new thermostats (the longer one in the front) and reinstall. Make sure the drain holes on the thermostat are to the rear of the truck.

Remove the bleeder screw on top of the thermostat housing (circled in picture).



Add coolant to the coolant tank on the passenger side between the air box and battery. Mine took about 3/4 of a gallon.

When full, coolant will come out of bleeder screw, when this happens, replace bleeder screw and top off tank to appropriate level.

Hope that helps! It's a pretty easy task, only takes about 1 1/2 beers :drink
 

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i just replaced mine based off your directions... thanks a bunch! made it real easy. only thing to change is that the torx screws are t27 not t20.

thanks again
 

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Used this to do mine on my 06 LBZ last weekend. Wasn't hard at all. Couple bolts were a pain to get to but I got it done. Thanks!
 

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Excelent pics - bookmarking this.

Thanks!
 

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Only 1.5 beers?? I'll get 2 down before I got the hood open:drink
 
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Premis, thanks for the write up. I notice mine not coming to operating temp anymore. And it comes up slowly.

What is the stock thermostat temps??
 

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Thanks a lot! This was great to use on my lbz. Only difference was the oil filler neck had to be removed ( only 3 bolts) and no drain on my radiator so I pumped 2 gallons out of the reservoir box into a couple jugs and didn't lose any coolant. Thanks again
 

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See attached pictures.
* Had to remove these brackets so we could pull the thermostat cover off.
* thermostat cover pulled off.
* I also pulled the oil fill tube out. Not sure how you can pull the thermostat cover off without doing that!

Thermostats Part number from O’Reilleys is #44748
Hope this helps anyone. This truck is a 2007.5 Chevy Silverado 2500 HD duramax 6.6 LMM
 

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Premis, thanks for the write up. I notice mine not coming to operating temp anymore. And it comes up slowly.

What is the stock thermostat temps??

180 and 188, replace them both at the same time.

One is long the other is short. Note which was in which location and replace the same. It is foolproof though, the long one will not fit in the short location. >:)
 

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180/185
 

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The easiest way for me to change the thermostats was to remove the bracket on the top of the thermostat housing, remove the oil fill tube and just remove the thermostat housing. Didn't need to remove anything else on my LBZ. Just remember to get new orings for the thermostat housing to upper radiator pipe and oil fill tube. I always change the oring for the thermostat housing to radiator pipe when doing this job. Use a little dielectric grease on the oring so you done roll or damage it when putting it back together. You don't have to always replace the oil tube oring. I just keep one on hand just in case the original one is bad when removing / installing the oil tube back in.

After the install of the thermostats, I install the housing back on and torque the bolts leaving the thermostat bracket off. Install the oil fill tube back on. The do the bleed process. With the thermostat bracket on you can't get to the thermostat bleed screw. And when your bleeding the air out, you don't want to get coolant in your oil so that is why I reinstall the oil fill tube.
 
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