coolant temperature sensor replacement envoy 2005 - Page 3 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 General Tech Q&A > General

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Old 04-20-2011, 08:31 PM
Daddy Mitzo's Avatar
Daddy Mitzo Daddy Mitzo is offline
2005 GMC Envoy SLT XL
Black 4.2L I6 4X4
Join Date: Feb 2010
Location: Montreal
Posts: 262
you don't need no special tool, I used a regular 18 key and on a certain angle i got it out and the new one back in and yes it was tightly secured
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Old 08-04-2011, 01:35 AM
GreaseMonkey's Avatar
GreaseMonkey GreaseMonkey is offline
Junior Member
2005 GMC Envoy SLT
Summit White 4.2L I6 2WD
Join Date: Jul 2009
Location: Los Angeles
Posts: 7
Originally Posted by edddie View Post
There is a special tool required for the removal of the coolant temp sensor on a 4.2 envoy 2004. That is a slotted 18mm deep socket. Good luck trying to find one....I had to make my own because none of the parts stores had it.
Hey fellas, for those of you who chose to make your own 18mm slotted socket, how did you do this, exactly? I'm stuck trying to refit a new coolant temp sensor on my '05 Envoy 4.2, can't seem to find the right angle with my wrench without rounding out the bolt and I certainly don't want to do that. :/ A little help, thanks!
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Old 08-05-2011, 01:40 AM
GreaseMonkey's Avatar
GreaseMonkey GreaseMonkey is offline
Junior Member
2005 GMC Envoy SLT
Summit White 4.2L I6 2WD
Join Date: Jul 2009
Location: Los Angeles
Posts: 7
How To Craft Your Own Coolant Temperature Sensor Socket

Okay, I've been mainly "lurking" and learning by reading this forum for the past couple of years since I joined and it's been a terrific resource for me, has helped me complete more than a couple of tricky jobs on my '05 Envoy SLT 4.2. So, it's time to pay it forward and here's my humble contribution. If it helps just one average driveway DIY'er like myself, then I'm certainly happy to have been able to help!

The coolant temperature sensor install on an '05 Envoy 4.2L (and a few other model years I gather as I read through the forum) really *does* require a special tool to remove and install properly. I understand that some here have been able to accomplish this feat using a simple wrench but honestly, I'm just not sure how -- I couldn't do it myself and believe me I tried it and at length while uttering *all* of my dear departed dad's infamous "golf" words in the process. So, what is required (as has been reported above) is a slotted 18mm deep socket, much like those used to remove and install standard oxygen sensors. The problem is, your standard O2 sensor socket comes in a 7/8" or 22mm size -- much too large for your 18mm coolant temp sensor install. You can call any parts store you like anywhere in (and out) of town but the only place on planet earth you're going to find the tool you need for this job is in a GM service bay. Or your home garage, if you make one yourself. And that's my purpose for writing this post.

Before you disconnect your Envoy's battery to start your DIY job, go on out to your fave parts store *first* and get yourself an 18mm deep socket (must be "deep", you'll need the added length) and the cheaper the better. Mine was a Craftsman beauty that it pained me to mutilate, but my Envoy was already in pieces in the garage at the point I discovered my dilemma and the local Sears was only a hop on foot away. Okay, so you've got your socket? While you're out, make sure you've got a bow saw with a blade rated for cutting metal pipe and a workbench equipped with a good-gripping vise and you'll have essentially all you need to make your modified socket.

Secure the socket in the vise at a 45 deg. angle *or* secure it parallel to the ground and stand over it to give yourself a good view of your target. You'll want to make your cut at a 45 deg. angle to the socket so as to slice through the one side of the socket and not the other. Cut about 3/4 of the way down the socket, then reposition the socket in the vise and make an identical cut parallel to the first, about a 1/4 inch apart from it. Do the same again, making a third cut about another 1/4 inch from the second one. When you've done all this (took me about 30min going easy but steady on it), grab a chisel and hammer and start to wedge the two small strips between the three cuts you've just made outward so that you can eventually use a pair of pliers and wiggle them right off of the socket. These sockets are hardy and strong, but they *will* yield to a bow saw with a metal-cutting blade and once you've made your cuts, those middle strips will just bend and break right off with a little encouragement. Voila! You now have your very own 18mm slotted socket and the very thing that will make the job of removing/replacing your coolant temp sensor hundreds of dollars less expensive than having the dealer do the job for you. Boo-yah.

I've included a photo of my finished 18mm slotted socket (below). Ain't she a beaut? No, you can't have her. I'm keeping her in hedging my bet that I may have to do this crazy job again someday. Good luck all, piece o' cake!
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Old 02-03-2012, 12:13 AM
KNBlazer's Avatar
KNBlazer KNBlazer is offline
Senior Member
2004 Chevy TrailBlazer LS EXT
Steel Gray Metallic 4.2L I6 2WD
Join Date: Sep 2005
Location: San Diego, KaLee-Fo-nee-ah
Posts: 814
Well I just did my temp sensor, not because it was definitely bad, but because it was a good idea as I am on my 4th AC Delco Thermostat in the last 6 years... Yes the temp sensor is a pain to take off, it took me about 25 minutes to take off and another 20-25 to put back in... I used a crowfoot flare nut socket, I think that's what it's called... the thermostat itself took me less than 5 minutes to take off and another 10 or so to put back in ... top bolt I did through the top and bottom bolt with 21 inches of extensions through the wheel well, there are tools that make it easier in taking that bottom alternator bolt out, a ratcheting combo wrench, craftsman sells it for $20... next time I am going to buy it, on the sensor socket, I see there have been some available, but are no longer available, I think I am going to visit a machine shop and see how much they want to notch a craftsman 18mm deep socket, ... most time consuming was that bottom alternator bolt.... dumb GM engineers, my 87 Pontiac, I can change the thermostat, change the oil, hell probably pull the engine before an ice cube is made... .. total actual labor was 3.5 hours ... total was about 5 hours, messing around...
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Old 01-31-2014, 12:15 PM
faithandjoesmom faithandjoesmom is offline
Junior Member
2003 GMC Envoy SLT
Summit White 4.2L I6 2WD
Join Date: Nov 2013
Location: Las Vegas, Nevada
Posts: 3
I want that tool!!

Hey GREASEMONKEY, I need your socket!!! Great job, and it doesnt have to look pretty as long as it does the job!!!! Thanks for the info. Patricia
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Old 02-03-2014, 02:47 AM
GreaseMonkey's Avatar
GreaseMonkey GreaseMonkey is offline
Junior Member
2005 GMC Envoy SLT
Summit White 4.2L I6 2WD
Join Date: Jul 2009
Location: Los Angeles
Posts: 7
You're most welcome and glad to be able to help!
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Old 04-03-2016, 05:25 PM
pwg pwg is offline
Junior Member
2006 Chevy TrailBlazer LS
Sandstone Metallic 4.2L I6 4X4
Join Date: Apr 2010
Location: new hampshire
Posts: 1
No need to use slotted socket?

I recently got the p0128 code and I cleared it. It has stayed off for about 700 miles now. I do plan to change out the thermostat and may as well do the sensor while I am in there. I will also probably replace the alternator while I have it off, as at 167,000 miles it is probably getting long in the tooth.

Thinking about the sensor, since it will not be reused, why not just cut of the wires and use a regular 18mm deep socket to remove it? The new one would be tightened with an open end wrench. Am I missing anything?
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