How to step by step Thermostat Replacement Chevy Trailblazer 4.2L Vortec 4200 Fix Repair 

If this video helped please let me know in the comments, Also Hit the Like Button & Subscribe! Thank you for watching!!!

Very good video, I am a woman and never worked on a car before . I have now done two hub assembly starter alternator front drive shaft brake's and rotors. Gives me satisfaction to do work myself. Thanks for the instructions!

Nice video, I didn't take all those steps. I took off the driver's side wheel and removed it through the upper control arm. I saved myself a lot of time and money. Thanks

Before I buy a used car, I like to get an idea of the DIY jobs that I can expect to have by watching videos. I really like the structure of the video. Pointing out your steps w/o having to watch you wrench each bolt. The video was lit up nice and clear, with good views all the way through. People like you give the confidence to people like me to take these type of projects on. Having one disabled hand that likes to drop things I would probably magnetize my socket for those bolts I fear dropping. Keep up the great work.

I was an HVAC Eng at GM, this video is spot on. Don't blame the engineer, it's all about the engine first then the/routing and eventually the assembly first build. Nice video and accurate.

One of the best repair videos I've ever seen. Job went faster and easier than expected.

This is the best "How To" video I have ever seen. Perfect. Thanks.

Most detailed and thorough video I've seen, thanks man, using it as a refresher I'm ready to tackle my envoy, done this before on my mom's trailblazer , but didn't think about using the wheel well method, and yep I lost that bracket bolt bein the alternator, won't happen again , God bless

Great video! Just finished changing mine on an 05 trailblazer. The video helped speed it up since I didn't have to dive in without a plan. Thanks!!

Nice video. I have a 2004 trailblazer and I've had TWO thermostats replaced. When the shop told me the car needed a new thermostat, I was all ready to do it myself. I come from the days where all engine blocks had the small diamond shaped cover..with the dome on top....always on top of the block at the front. It was loosen two bolts..pull the cover off, pull out the old thermostat, put in the new, put the cover back on, then tighten two bolts. It was literally a 5 minute job. When the shop told me you had to take the alternator off....I told them to do it.

Going to attempt this repair tomorrow, your vid was very helpful and informative. exactly what I was looking for thanks for posting

VERY DESCRIPTIVE! VERY INFORMATIVE! THANK YOU! Gave me the confidence do it!

Perfection sir!. Perfect edit with no wasted time, and thanks for all the extra tips

This video was the best I found for doing this job. I am a RU-vid mechanic and was able to follow along and get the job done without any issues. My 07 Trailblazer had a rigid line next to the bottom alternator bolt. Maybe for the transmission fluid cooler I don't know but I could not come through the wheel well to unscrew that bolt. I used a combination wrench and a lot of patience. Anyway thanks Steve you saved me some money.

Excellent video; concise yet thorough.

Thanks for the tutorial. The way you show and explain the process makes it easier for me to replace the thermostat on my own saving lots of cash I can't afford. Once I check that I have the proper tools I will go to work on it. Hopefully I will find this video again and be able to let you and your viewers how it went for me.

Thank you for the video. It helped me greatly in changing the thermostat in my vehicle. Getting the bottom bolt out of the alternator was a real pain because one of the hose was in the way and it did not give when I tried to move it.

No wasted time nice cut outs and perfect explanations.

Great Videos, very Clear camera & you are very thorough in the Instructions.Thanks much Steve !

This is definitely one of the better videos. I love your explanations without all the frills and fuss. We are about to do our 03 Envoy. Thank you. wish us luck lol.

Second video watched to help with the Trailblazer. Thank you!

This video was great. Really good explanation to how and why you were doing what you were doing. I have watched 2 other video to replace my thermostat, but none as clear and detailed as this one. I will be changing mine tomorrow. GREAT job!!

Thank you so much! I literally just finished getting the Thermostat switched in 05 Chevy Trailblazer thanks to your tutorial. For some reason my fender well was way tighter so it didn't work but I 2 clicked it since you showed the alternative. My hands and forearms got tore up from that annoying battery tray. I think I may have overfilled my reservoir because after driving back it was leaking but then it stopped. I hope that's what it is and not a leak. Again thanks Steve Young, you weren't just a great QB but a great RU-vidr.

Great video! One of the best RU-vid videos I have seen. Thank you so much!

Best video out there on this subject. Well done and thanks for putting the time in , so we could save time!

Getting ready too change mine. Very informative thank you!!!!!!

Doing this tomorrow. Great job, thank you

This video was a great help , thanks for the awesome detail explanations

Thank you for this video this was the guide on which I had to switch out our thermostat on our Trailblazer you definitely gave great step by step instructions and I felt very confident watching the video before I even started this job you save me about 300 bucks at Pep Boys here in Arizona and other shops about $250 at other shops but thank you again keep up the great work

Thank you for this video! You now have another subscriber. At least on the earlier models of the Trailblazers, the locations of the thermostat and the Engine Coolant Temperature Sensor (ECTS) are in the same general area: below the alternator! Sometime during the production of the 2007 model year, on the new Envoys and Trailblazers with the I-6 engine, in their Greedy Wisdom, GM made a design change. On my 2008 Trailblazer with the I-6 engine, GM changed the location of the ECTS, placing it way back under the firewall cowl, on the left side (Passenger Side) of the cylinder head, and very close to the left rear corner, where it cannot be seen w/o an endoscope! I had to buy an endoscope that connects to my I-Pad to verify the location the ECTS, and and also to assist me in replacing that sensor. All of the air intake duct and the heat shield on the exhaust manifold has to be removed. The plug in the wire harness that connects to the ECTS is mounted on top of the valve cover very near the back of the cylinder head. The wiring harness to that plug is very short... so short that once the plug is broken free of the valve cover, you cannot bring it forward far enough to separate the male plug from the female socket easily... a couple more inches of wire would not have cost GM that much! I know all this because I had to replace that ECTS on my 2008 Trailblazer. Tomorrow I will be replacing the thermostat and its housing on my Trailblazer... using your most-excellent video as a guide. In closing, I state that the vehicle-specific Haynes Repair Manuals of today are sure a sorry excuse when compared to the excellent repair manuals they used to be.

Thanks a lot, this video saved me a lot of money! Very thorough.

I have had the misfortune of having to do this job more than once. As a refresher I pulled up this video and it is by far the best one I have seen on this topic. The tip on how to get the bottom alternator bolt was especially priceless and I agree having the battery out of the way greatly simplified this operation . Thanks for such a great video!

Definitely a helpful video. I have to change my thermostat and my alternator! Fist bump from Columbus, Ohio 🤜💥🤛

Excellent video! Thank you for going step by step.

great video, lots of detail. Thanks for posting.

Excellent video sir. Thank you for the quality, detailed content.

Thanks Steve, got this job coming up!

Thank you for this video. I used it to change out my thermostat. I wound up taking out my battery just to help get the alternator in and out.

He helped me a lot with his video, it's very good.

Thanks to you I got the truck up and running again didn’t have To take off the fan for the housing it was pretty in and out hope you do more videos on that truck so I can take a look thank you my God

I watched other videos and yours is the best.

This is very informative and saves me the time and trouble of taking the top one off and finding out it's not up there ugh... WHY???? LOL... but glad I watched this and its not so bad. I'm going to be starting on mine THANKS FOR THE VIDEO!!!

Great video now I know how to change a thermostat and take off a belt and also a alternator

I’ll be putting on a new belt and pulley after thermostat install. Bad ass man. Watched your video twice im ready to go

The video was a great help. The only problem I had was removing the bolt on the bottom of the alternator. All my wrenches were too long and a socket would fit because of the AC line. I ended up cutting my 15mm wrench in half and got it out. Once I got it out it was quick to put it back together.

Thanks for the video, it really helps a lot!

Thanks awesome to the point video, I just saved $350.00 by replacing the thermostat on a 2008 GMC Envoy.

Thank you thank you thank you, Excellent video saved me a whole lot of guessing and more important time.

That was a very nicely done video. For somebody who’s not a professional video editor or a professional mechanic, I found this be quite helpful. If I could make a couple recommendations they would be invest in an air compressor and a good quality 3/8 air ratchet and 3/8 impact gun for jobs like this. They would’ve cut the time in half. Alternately a rechargeable impact would have been helpful on many of those bolts if a compressor and air tools are not in the budget.

This video was very efficient thank you

Excellent video !

You rock brother, took me awhile cause a bolt broke and I flushed the coolant.

Very helpful video thank you man

Thanks good video helps alot of people.

These are only 10mm bolts. You don’t have to put the fear of God in them. 😂😂😂

Excellent video! Thanks much.

Thanks buddy your video helped me do the job.☺

Dude, very good video. 👍

Good job. Thanks for the info.

Thanks for posting this, I think my thermostat is bad. The car was overheating and making a thumping noise. I’m gonna change it this weekend!

Great video! Can't believe you did all that and didn't replace the lower radiator hose!

Thank you so much for posting this instructional video! I'm a divorced mum with kids and you just saved me $$! Also this video is great for folks needing to replace their Chevy trailblazer alternator. #ChevyTrailblazerAlternatorReplacement #ChevyTrailblazerThermastatReplacement

Dude, I didn't know about going through the fender well, to get to that damn bottom alternator bolt. Thank you!!!

Good vid Steve. If I have to replace mine I think i can follow that process...

Thanks bro! Definitely doable!

thanks bud ur video help me to much

Helpful video. My AC hose bracket was not moving like in the video, so I bent it out of the way. Its aluminum, and easily bends back and forth with no problem. Impossible to get the alternator out without doing this.

Just did it..thanks 4 tips

Great video! Thanks for doing it

Nice job Steve.

Awesome video dude. You just wanted a new subscriber.

Thank you kindly sir for your video! You saved us 200 bucks! 👍 a couple bloody knucles and a few F bombs but shes running like a champ! Liked and subscribed!

That’s really good learning

Awesome video thank you for your time god speed

Thumbs up and thanks for the tips.

great video thank you.

I liked this video because it showed me I dont want to do this job myself!

Thank you for your video

Great job, I am having this problem and as soon as time allows and parts are purchased I will dive in and save a few bucks by not taking it to the shop

Very informative.

Great video

This really helped me out, thanks a million. Only issue I had was the bottom bolt on he alternator, my '04 had a hard cooling line in the way so I had to use a gear wrench instead of going through the wheel well. Everything else was super straight forward thanks to your video.

Thank You for the great video.. looks like I have to do this next on my Envoy.... I appreciate your concern for the environment, too. Animals like to lap antifreeze up- and it will kill them.

I just had to do this to my envoy today.. I used one of those extendo magnet to set that back bracket bolt

Great Video 👍👍👍👍👍👍👍

Thank you for this video ! It helped a lot :-)

Gotta 02 Envoy. Engine light on, Auto Zone code reader said t-stat and housing... Temp not warm enough... Now I know what I'm in for... Thanks

EXCELLANT AND THROUGH!!!

Excellent!!!

I changed my alternator with out removing the bracket and it was a pain never again. thanks

Thank Bro

nice video

Its actually easier if you remove the l/f wheel and go through the fenderwell with a long 1/4" extension

Going in from the bottom for that under bolt it may also be easier to turn the steering wheel all the way to the left as well. That way the tire itself won't be in the way either.

Good stuff

Helpful vid, tu

I learn from that thank,,,,

Great video saved me 160 bux shop wanted 190 bux I called for the part only 25 bux so shop wanted to charge double for the part

Great video. I know how too do it now. A suggestion to you and your viewers buy a Milwaukee m12 3/8 rachet . You still have too break the bolts by hand its a saves time and frustration.

Note to DIY-ers, when loosening the belt tensioner, look where the poster places his ratchet AND look that he does not have a socket on. You just place the naked 3/8 ratchet into the female square next to the bolt on the belt tensioner. I broke off my belt tensioner due to my own carelessness and not paying attention to the ratchet placement in the video. Successfully changed my thermostat though!