Thermostat & CTS Replacement

Happy Hummer

2007 Hummer H3 Thermostat & CTS Replacement.

So I've been having allot of issues with the temp gauge inside of Happy Hummer floating or wondering, if you like.  Tried to wait it out til summer and thankfully the truck held together.

• The first thing we need to cover is the correct items to order and there part numbers (purchased off of Amazon.com and included s/h)

Part #'s:

• Thermostat: GM part#:12622316 or 12579958  ACDel part#:15-11073

• CTS: GM Part#:12601050  ACDel part#:213-4233

• The second thing to cover is SAFETY.... Cant stress it enough!  Do Not do this with out jack and jack stands if doing it in your own drive. Prepare the work area and leave plenty of time.

• I'd strongly recommend putting heavy duty rubber gloves or work shop gloves on for this job. You'll also need a dish pan, oil pan or 5 gallon bucket for catching fluid. This job is messy so have some shop towels and a hose handy.

Now that we have the parts listed lets talk about the actual install.  First of all it takes allot of patience and about 4 hrs. of time to do the entire job from start to finish.

• Remove drivers side tire (19mm socket)

• Begin removing all plastic snap push pin from drivers side wheel well ( a flat head screw driver works really well)(conversely you could buy the special purpose tool)

• • You will now want to remove the under armor to aide and assist in the thermostat replacement

  • With the armor out of the way you'll be able to loosen the bottom radiator clamp on the drivers side closest to the bumper

  • Remove the hose from the radiator bottom outlet and catch as much fluid as possible in your pail

• • Now comes the gymnastics....you have to some how get your arms and hands into the area in the drivers wheel well and remove two (10mm) hex head bolts.  Now I'm here to tell you that I've scratched my head on some manufactures designs but this is a total nut buster to work on.  Firstly the sockets and wrenches were a bitch to fit and the fluid is all over everything so it is slippery. You can try to go from the bottom but that is better left to a contortionist or you can go from the wheel opening but you'll run out of room to work. I found that a large size 3/8, 1/2 or 1/4 driver extension of approximately 6-12" works best.  I also needed allot of swivels and pliers. I had at least 20-30 tools out just to find one that would fit.

• • Once you get the thermostat housing out you can then remove the hose.  I found a flat head screw drive wedge in and some silicon spray did the trick.

• Now comes the interesting part... When placing the NEW thermostat in the opening make sure you place the air bleeder whole up.  There is a small time dial etched into the face of the thermostat housing and a notch that is unmistakable. I must of spent 30 mins. trying to figure this out.  The replacement housing is slightly redesigned from the o.e.m.

• • Wrestle the hose back into place and slide it onto the thermostat housing and allow the compression spring to close. Don't forget to get it all lined up on both ends frist and make certain the hose are pushed in all the way and then release the compression spring clamp.

  • Double check all of your bolts and clamps.

  • The next step is to do a general once over cleanup and organize things for the coming steps.

  • Were now going to remove the flexible hosing for the resonator assembly for the air intake.  You'll want a 1/4" driver and 5/16" socket.  Loosen the four screws for the bands on the hosing and then using a 3/8" driver and 6-8" extension with 10mm socket loosen the two bolts holding air resonator box. Don't forget to take off each breather hose and also the small black PCV hose from the top of the engine. 

• Next comes the real fun. Remove the locking clip on the CTS plug and unplug the unit.  O.K. this sounds easy but in reality is a bit of a bitch.  I found a small flat head screw driver and allot of patience is the best medicine here.  DO NOT rush!  If it seems like the clip lock wont come out take a break and try again.  If it feels like the plastic push tab that goes into the engine top to keep the CTS in place wont budge take a different approach too it.  PATIENCE!

• Here is where it got real interesting. We went to three different places and they had NO tool to fit the 2007 Hummer H3 CTS bolt pattern. I was actually dumbfounded as to how to remove this sensor without a tool that would fit.  Wasted better part of 1 hour running to and fro.  Bought some crows feet metric wrenches and they will not fit.  In the end cut the side out of a 5/8" spark plug wrench and used that.

• • Install new CTS and reverse you steps you just did to get to it.

  • Replenish your fluid.... Dexcool....

• • Start your Hummer H3 3.7L engine and allow it to get to operating temperature. PRAY you have NO leaks... If you don't Pray maybe do a chant.

If everything looks fine and nothing is leaking reinsert your wheel well liner and replace tire.  

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