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2003 chevy trailblazer_lt_ext
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Discussion Starter · #1 ·
Well, after popping a code P0128 a few weeks back, I found the instructions and inspiration to change my thermostat myself last weekend. BIG SHOUT OUTs to :

Double D --- http://forums.trailvoy.com/showthread.php?t=54225&highlight=thermostat

and rbarrio -- http://forums.trailvoy.com/showthread.php?t=32326&highlight=thermostat

Both methods were helpful, and once again, this site proves to be invaluable in the money saved on repairs, and the increased life of my TB!

I gathered all my tools as well as the new thermostat, 1 gallon of dexcool, 1 gallon of distilled water, and a new serpentine belt (to replace the original!!)



1 - My first step with all repairs is to disconnect the battery. I like to tie my negative cable back, just to make sure it does not contact anything while I am flopping around under the hood.



2 - Remove the serpentine belt. I used a breaker bar with a long pipe over the handle. It gave me plenty of leverage, and it was easy as pie to push it with one hand, while pulling the belt off with the other.





3 - HELPFUL TIP :thumbsup:to remove the alternator, I first removed the bracket, and then removed the two top alternator bolts. THEN, since I was working alone, I grabbed a tie down strap I had laying around, and wrapped it around the A/C hose that snakes in front of the bottom alternator bolt, and then fished the ends of the strap down through the left front wheel well. I pulled my battery, and used that to pull the strap just enough to keep the hose out of the way. From there, I could easily get to the bottom bolt. See pics!!











4 - Disconnect the wires from the back of the alternator, and then slide it/maneuver it to either pull it out, or in my case, move it enough to gain access to the thermostat, which should now be completely visible.



5 - at this point, it was easier for me to remove the thermostat while still connected to the hose. I removed the top bolt from above, and removed the bottom bolt through the wheelwell.





Be prepared for coolant to spill all over once you loosen and remove the t-stat. From here, I found it easier to turn the hose so I could remove the clamp and the old t-stat. Here is the old one... WIDE OPEN, just as expected!!



Old vs. new part. MADE IN CHINA.. on my Chevy!:hopeless



Putting everything back together was too not hard, but like everyone else, I dropped the bottom bolt when putting the new thermostat on. I finally figured out I could wiggle my hand in there and start the bolt by hand, then go through the wheel well again to tighten it.



Here is the new serp belt. Make sure you get the right one. I have an EXT, and this one went on easily.



And here is my result! After a coolant drain and refill - No more SES light, and all the gauges look good... except the fuel gauge! haha.



I do hope this was as helpful to someone as the posts that inspired me to do this job MYSELF!! Now get out there and don't come back without some scrapped knuckles! :tiphat
 

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2003 chevy trailblazer_lt_ext
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8,770 Posts
Great pics! I'm doing this tonight! :D
 

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2006 chevy trailblazer_ls
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286 Posts
Congrats on a job well done....
 

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2002 chevy trailblazer_ltz
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2,762 Posts
Nice job,but I would change the censor (over top of stat) at the same time.It's cheap and you'ld hate to rip it all apart if that was /or part of the problem.
 

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2006 chevy trailblazer_ls
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541 Posts
I tucked in old rags where a thermostat bolt could land. saved me lots off time because I dropped a bolt at least six times.

Also, next time I have to go back in there. I am going to double clamp where the hose slides onto the thermostat.

Good idea on tying back the battery cable. Somehow mine wandered back and was making full contact once again. I thought pushing it way back was enough but nope. One could also probably just throw a heavy cloth over it if you have nothing to tie it back with.
 

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2003 gmc envoy_slt
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9 Posts
This writup should be stickied. It is clearer and easier to follow than the others on the site.

I wish it would have been here a month ago when I changed the Tstat on my Envoy. It took me 6 hours and All of my cuts/scrapes/bruises have just recently healed.
 

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2004 gmc envoy_sle_xuv
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192 Posts
This writup should be stickied. It is clearer and easier to follow than the others on the site.

I wish it would have been here a month ago when I changed the Tstat on my Envoy. It took me 6 hours and All of my cuts/scrapes/bruises have just recently healed.
:iagree: Sticky please, awesome tips, excellent pictures, and extremely clear write up. I just changed my thermostat at the stealership today. Scary price, guys, compared to buying my own thermostat. Didn't want to tackle the problem myself since I have 4WD and I heard its a lot harder to get the bottom bolt with the drive train in the way. But when it comes time for another new thermostat I will definitely try to do it myself. :tiphat Thanks O.P.
 

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2004 gmc envoy_slt
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18 Posts
Thermostst replace

Good write up.Basically the same procedure I followed. I encountered a problem with the center dash vents not working after I disconnected the battery. I had to replace a cooked actuator. Apparently related to the battery disconnect. I'm wondering if placing the hvac controls in the off position and removing the hvac fuses prior to disconnecting the battery may have prevented the actuator problem. Any thoughts on that from any experts out there?
 

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2003 chevy trailblazer_ls
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5,268 Posts
good to see another successful TM change.
 

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2003 chevy trailblazer_ls
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Good write up.Basically the same procedure I followed. I encountered a problem with the center dash vents not working after I disconnected the battery. I had to replace a cooked actuator. Apparently related to the battery disconnect. I'm wondering if placing the hvac controls in the off position and removing the hvac fuses prior to disconnecting the battery may have prevented the actuator problem. Any thoughts on that from any experts out there?
Not an expert, but I have a memory saver I bought at AutoZone, as I have heard many stories of ac problems after a battery disconnect. The item pugs into the odb and has a cigarette typ power plug. I have an old 12 v dc power supply that I clipped the wires on, put on spade clips, connected to a socket to power the device. If you had another car nearby and an extension you could plug it in to the other car, making sure the socket is powered.

Great tips on the thermostat, I have the p0128 pending code. The temp looks normal. The temp has always been a little below (1 tic mark, maybe 2) 210 in normal driving, and seems to be holding steady. I'll keep an eye on the temps the next few trips. I thought if it was easy enough I would just go ahead and replace it, but now I want to be convinced it is the problem. Thanks again, I never would have found the thermostat alone.:tiphat

I had 3 other B codes that said History. Does that mean the codes have cleared?
 

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2005 chevy
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...The temp has always been a little below (1 tic mark, maybe 2) 210 in normal driving, and seems to be holding steady...
When mine was running like that, the actual temp according to my scanguage was about 175. MPGs suffered a bit, I was much happier after getting that fixed!
 

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2003 chevy trailblazer_ls
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106 Posts
OK I'll replace the fuel filter, (30k 3 years) though the last time the purolator filter had a larger diameter than the oem, so I zip tied it in place, as the plastic container would not close. I'll go for the OEM this time. Apologies in advance if this is considered hijacking a thread, but it was in your moniker!

Thanks for the info blackshadow, I will take it to heart
 

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2004 chevy trailblazer_lt
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84 Posts
:thumbsup: Great write-up!! I attempted this on my TB about a month ago when I replaced the fan clutch, it was a PIA and I didn't even get it done :hopeless After reading this though, I think I can try it again!! Thanks a TON!!! :hail:
 

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2003 chevy trailblazer_ls
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106 Posts
I got lucky today, my ses light went off, after temp too low code. Temp rose normally with a slight pause at 160 degrees or so. So I am going to put off thermostat and sensor replacement for now. Sorry to bother you with trivia but working my way up to 20 posts so I can join the locals! It has always been at least 1 tic mark below 210, but as it is a 195 deg thermostat I would think that normal. 115k. Dumped dexcool for peak global at 86k.:raspberry
 

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2003 chevy trailblazer_lt_ext
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TStat

Nice write up and thanks for more pix. I'm a visual learner so the more pix, the better. I too just replaced the tstat...took about two hours ( I was a mechanic in past years). I found that removing the batter and battery tray made life easier. It also gave me the opportunity to clean that thing out! I completely removed the alternator too. Crazy stats...dealer thermostat was 58.00 and coolant temp sensor was 68.00. Local parts house t-stat was 28.00 and I returned the sensor unopened to the dealer. All is well....except for the evap SES code...fuel cap seems to come off all by itself! Any known modifications on the fuel cap out there??!!
 
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