Tips on 1st Thermostat replacement on Inline-6

#1
Time to replace that pesky thermostat that's driving you crazy with the P0128 code? Listen carefully boys..it's not IF it will ever happen to you, it's WHEN will it happen?

Sooner or later we all have to do this job-from-Hell. Here are some tips to make it less painful:

1. Don't plan anything else that day. Buy some beer and go easy on the caffeine. (think Divorce Court)

2. Wear gloves. They won't stop all the bloodshed but you won't frighten the children so much.
PS: your forearms will still get scratched up.

3. Watch all the YouTube videos you can find. Learn from others who have been there.

4.First obstacle you have to get through (after removing the serpentine belt) will be removing the Engine Hoist bracket with the, barely visible, hidden third bolt. Use a medium socket wrench extension. Good job...pat yourself on the back!

5. Now comes the tough part... removing the alternator. That's right...you're doing an alternator removal too. Isn't this fun? Think the hidden engine hoist bolt was awkward? That was your warmup set! Remember...you can't even really SEE the Thermostat yet!

6. Crack open a cold one and get ready for the dreaded lower alternator bolt. The top two bolts are simple. Great engineering-the alternator will always be lined up perfectly with the other pulleys. But you're doing the lower bolt basically blind. You can't put a socket on it because when you try to back the bolt out you run into the AC pipe. A ratcheting 15mm box wrench will work from the side but you can't remove the wrench until the alternator is disconnected. The loose bolt and wrench have to stay with the alternator until it is removed and there's room to get them out. I bought a stubby 15mm open-end wrench and took my time, doing it blind, with small gains with each short turn.

7 . Finally! There it is... the Thermostat. Two bolts, one hidden, (of course) and off it comes.

8. Now is a great time to replace the lower radiator hose and get rid of those mousetrap-like factory radiator clamps. Also, replace the coolant sensor while it's easy to get at (right above the thermostat). Really...just do it. You don't ever want to have come back here again!
 

DAlastDON

Well-Known Member
#2
I haven't done the thermostat yet but will before the cold weather comes back. Ran a lil cool last winter so i went ahead and have an ac delco replacement. Couldn't be any worse than replacing the timing chain tensioners on a 07 maxima with the engine still in. To me, that was a tight spot.
 

Lckent48

Active Member
#3
It can be done through the wheel well, but I'm not sure if it is any easier. PIA anyway you look at it. You'll need really skinny arms or long socket extensions.
 

Mounce

Silver Supporter
#4
Pretty sure both ways are a major PITA so you just have to pick one and run with it lol. You'll never know if one way is easier than the other unless you replace it twice and try both methods.
 

freddyboy61

Well-Known Member
#5
Just a piece of information, on 2006 and above models the temperature sensor is located on the passenger side of the engine towards the rear. A figure is attached.
 

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#6
I have done this a few times now, the last time being 40 minutes start to finish. It is really not that bad after you have done it once. The first time i did it I was furious for about 3 hours :Yes:

(I am pretty sure i invented a few new curse words that day)

I can take the alternator out in about 5 minutes with an air ratchet, 15 with the ratcheting wrench. BTW you do not have to take the alternator all the way out, just move it forward to gain access to the temp sensor and upper thermostat bolt. for both of those items 24-ish" of extensions though the fender opening makes it a very simple job.

:tiphat:
 

Texan

Well-Known Member
#7
I replaced my thermostat a couple of weeks ago.
I recommend that you place a rag under that hidden
bolt under/behind the engine hoist bracket. My bolt fell
out of the socket and down through the hole.
There is a hole in the I6 block under the alternator
that may be a real problem if 4WD.
 

AbsoluteZero

Well-Known Member
#8
Regarding item 4 in your list, the hidden bolt on the engine lift bracket. After wrestling with it for a disapportionate amount of time I slotted the bracket where that 3rd bolt goes after I got it off. That way the next time I just back out the bolt enough to let the bracket slid out. I've had to work on the thermostat and temperature sensor 3 subsequent times and found this mod to be handy. If I ever were to need the bracket for it's intended purpose I'd need to take steps to weld the slot closed... maybe.
 

RPJ 03 Envoy X

Well-Known Member
#9
I would agree with the information for the most part. I just did my water pump, t-stat, and temp sensor about 4 months ago. A couple of additional items to help you when doing this. If you have to do tem all as I did, removing the fan and shroud as a unit is not hard and gives you extra room to work.

1. Use bungee cords or rope to tie your hood out of the way while doing this.
2. The gloves for protection is at a minimum. If you can stand it, wear a lightweight long sleeved shirt if possible. I still have a 6 inch scar on my forearm to remind me. I think I got an infection from the dirty metal, but that was not confirmed.
3. Slotted (O2 sensor) socket for the temp control sensor to keep from damaging the wires. IIRC it is 18 mm.
4. Drink all you want after you are done. I lost the hidden bolt from the t-stat when reinstalling and it took some time to locate that sucker. I had to get another bolt and do a couple of test drops to see where the damned thing went.
5. If your Dexcool is relatively new/fresh, catch it in a clean container and put it back in the radiator when finished.
 

AtlWrk

Well-Known Member
#10
This information may be in other threads but this is the one I came across first while looking for help last night. Some additional crucial information
for 2006+ engine coolant temperature (ECT) sensors:
1. In addition to the sensor being in a different location for the 2006 MY, it is a different sensor too. It is physically smaller and uses a rubber o-ring instead of a copper washer. Make sure you get the right one--you don't want to have to stop halfway through to run to Autozone to get the correct one like I did. :Banghead:
2. The sensor socket size is 15mm in this case. A 15mm slotted/sensor socket is an absolute must. After fussing with other tools, none of which could get in there I gave in and stopped to make my own with a dremel and a spare deep socket. Do not think you can get away without one like I did, you will hate yourself in the end. With the socket it was trivially easy to reinstall the new sensor.
3. The sensor is blocked by the hard-line portion of the heater hose bolted to the rear of the engine block however the line can easily/gently be bent away to give you a straight shot
4. The exhaust manifold shield does not need to be removed (I saw this mentioned on another site)

All that being said, the new location seems inconvenient but with the slotted socket it's not really that hard to get to at all.


TLDR: get the right sensor, get/make a 15mm slotted socket.
 
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xavierny25

Well-Known Member
#11
@AtlWrk any chance you got a pic of the 06 and newer temp sensor. I ordered mine on rockauto.com so im hoping they got it right. I'll be tackling changing mine out this weekend along with my upper ball joints. I didn't get to it when I was changing out the t-stat on Saturday since I knew it was minutes from some snow falling.
 

AtlWrk

Well-Known Member
#12
I just checked Rockauto earlier and they do have the right sensor listed for the 2006. I actually did take a picture of both last night. You'll know you have the right one if it takes a 15mm socket instead of 18mm and has a rubber o-ring instead of a copper crush washer. In the picture, the one on the inside/left with the gray wire boot is the correct one for the 2006+.
 

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xavierny25

Well-Known Member
#13
I just checked Rockauto earlier and they do have the right sensor listed for the 2006. I actually did take a picture of bith last night. You'll know you have the right one if it takes a 15mm socket instead of 18mm and has a rubber o-ring instead of a copper crush washer. In the picture, the one on the inside/left with the gray wire boot is the correct one for the 2006.
It sure does look like what I have at home but I'll verify when I get back home this evening. Thanks for the pic and info.:2thumbsup:
 

Torker

Active Member
#15
I used a telescoping magnet to pull the bottom alt bolt after getting all the way loose. Damn thing ate my 10 mm deep socket. Any idea where to look ? :sadcry:
 

xavierny25

Well-Known Member
#16
I used a telescoping magnet to pull the bottom alt bolt after getting all the way loose. Damn thing ate my 10 mm deep socket. Any idea where to look ? :sadcry:
My Voy likes to hide my sockets aswell. Lol. I'd check the frame rail for the lower control arms I located 1 of my sockets in there when I did my lower control arms. I've also had fun trying to get my radiator cap and oil cap out of in between the fan and the radiator. The'll fall in there pretty easy but hate to want to come back out.

Edit.... or it could just have fallin on the bottom plastic cover for the oil pan. Just bang up on it a few times you'll hear it if it's there.
 

xavierny25

Well-Known Member
#17
I just checked Rockauto earlier and they do have the right sensor listed for the 2006. I actually did take a picture of both last night. You'll know you have the right one if it takes a 15mm socket instead of 18mm and has a rubber o-ring instead of a copper crush washer. In the picture, the one on the inside/left with the gray wire boot is the correct one for the 2006+.
that looks like the one i just got for my 09 from rock auto. mine has a black cap instead of gray. ACD# 213-4233, GM# 12601050 (from packaging)
Seems I've got the right temp sensor after all.:2thumbsup: 20170119_075251.jpg
 

AtlWrk

Well-Known Member
#18
That looks right :thumbsup:

Fun fact: my temps appear to be even (slightly) LOWER with the new sensor than they were reading before :Banghead: It used to struggle to get to ~192F. Now it struggles to get to 186F. That being said, I ran a series of tests and am confident it's not a sensor issue. I may have got a bum thermostat (AC Delco) out of the box--I've seen reports of that happening but was skeptical but I don't know what else it could be...

In short: new thermostat and new sensor, no change in behavior (actually slightly worse). <SIGH>
 

xavierny25

Well-Known Member
#19
Oh damn.... When did you change out the t-stat? So far the acdelco I installed has the temps reading at 194 to 200 after a 10 minute drive. I don't think the stant I put in ever got to these temps unless it was blazing hot out. I've been monitoring it with car gauge pro and torque just to see if they may differ but alls good. Now I'm afraid to change the damn sensor. Lol
 

AtlWrk

Well-Known Member
#20
Thermostat was a few weeks ago. It was only one test drive where the temps seemed to struggle to get to 186 and it may just be because it was only in the 20s out. It did have plenty of time to warm up though so in theory that shouldn't matter. My point being I should not have suggested that there is a problem with the new sensor--more that the problem persists despite changing the sensor.

My drive to work is ridiculously short now so I don't get a whole lot of chances to get good "fully warmed up" data points. What I do know for certain is that the temps I am seeing through Torque are accurate. All three sensors (the old one, the new one, and the new one that was the wrong part number) read dead-nuts on for their resistance/temp and the PCM outputs the expected temp for a given resistance (both from the sensor and while being jumped with a resistor of known value) so there's nothing wrong in the sensor, sensor wiring or PCM's measurement and reporting.
 
#21
You're not that far off. And don't forget you're also likely running the heater/defrost which takes heat away from the system. Mine runs between 190-194. If idling, it might not get up to full temp.
 

AtlWrk

Well-Known Member
#22
I agree it's not that far off, when it gets there, but with a new thermostat and sensor there's no reason it should be off at all?

Had a 30 minute drive yesterday, mixed highway and city. No heat running, 50 degrees out. Would climb to ~160 in no time at all, then slowly creep up into the 170s to low 180s (after 20+ minutes). Highest it got while driving was 186. I let it idle in the driveway for another 5 minutes or so when I got home and it hit 190. That sure doesn't sound right, does it? I know I used to get up to 194+ in less than 5 minutes in the dead of winter.

I thought my old thermostat was getting sluggish so I took the opportunity while I had to replace a pump to put in a new thermostat--kinda regretting it now.

I still have the thermostat I just pulled out that was behaving similarly (albeit with no lag in the 170-low 180 range)--I'll do a boil test this weekend and see if I can see anything strange. Some anecdotal evidence around the interwebs suggests that a low quality gasket maybe causing the thermostat to jam. Or maybe I have it torqued wrong and the deformation is causing it to stick?

At least I'm above the threshold for setting the cooling performance DTC so if I can't find a conclusive diagnosis maybe I'll just live with it. I do wish there was a way to confirm at what point exactly the PCM leaves fuel enrichment mode though.

(Sorry, way too much caffeine this morning :yawn: :coffee::coffee::coffee::yaay:)
 

coolasice

Well-Known Member
#24
I agree it's not that far off, when it gets there, but with a new thermostat and sensor there's no reason it should be off at all?

Had a 30 minute drive yesterday, mixed highway and city. No heat running, 50 degrees out. Would climb to ~160 in no time at all, then slowly creep up into the 170s to low 180s (after 20+ minutes). Highest it got while driving was 186. I let it idle in the driveway for another 5 minutes or so when I got home and it hit 190. That sure doesn't sound right, does it? I know I used to get up to 194+ in less than 5 minutes in the dead of winter.

I thought my old thermostat was getting sluggish so I took the opportunity while I had to replace a pump to put in a new thermostat--kinda regretting it now.

I still have the thermostat I just pulled out that was behaving similarly (albeit with no lag in the 170-low 180 range)--I'll do a boil test this weekend and see if I can see anything strange. Some anecdotal evidence around the interwebs suggests that a low quality gasket maybe causing the thermostat to jam. Or maybe I have it torqued wrong and the deformation is causing it to stick?

At least I'm above the threshold for setting the cooling performance DTC so if I can't find a conclusive diagnosis maybe I'll just live with it. I do wish there was a way to confirm at what point exactly the PCM leaves fuel enrichment mode though.

(Sorry, way too much caffeine this morning :yawn: :coffee::coffee::coffee::yaay:)
I used a Stant in mine and I get the same behavior
 

rizzo20

Well-Known Member
#25
I can vouch for the long sleeves and minding your sockets & bolts. My forearms were bruised and had a few scratches after this job. Ever since I became a bachelor again and got a desk job now I bruise like a grape......me and my soft dishpan hands.... also these Trailvoys eat dropped bolts and sockets like a mofo.

Anyways, I wish I would have read this thread before my T-stat replacement, I got it done but it would have been easier. I had no idea the '06 + up had the temp sensor relocation. I looked over and over for the old sensor with the new one in my hand and said F-it! I dunno where it goes! So I popped in the new Tstat and went on my way.

For the guys that have replaced the '06+ up sensor did you do it from under the truck or the engine bay? I tried to see the old one from the bay and I can't even lay eyes on it.

One more thing to add....with the old T-stat my temps were 174 tops in Torque (just to the left of 210 on the gauge) and now with the new ACD t-stat they top out at 190 on torque (just to the right of 210 on the gauge). I expected to be 195 - 205 from all the threads I've read, maybe its the cold weather here. If I ever figure out how to change the sensor I'll see if that changes my temp readings at all.
 

Torker

Active Member
#26
Glad I looked this up. I thought for sure it was in the neck going to the top hose ... Mine works great. Finally straight up on the gauge. And I finally breaking 18 mpg on most tanks. Use to be 17.5 now 18.5..
 
#27
Do you know where i could get one of those sockets? I need to get this done I have the part and have tried with a crows foot but no luck. I dont have any type of grinder or a way to create one of those. Thank you
 

Locksmith

Silver Supporter
#28
Do you know where i could get one of those sockets? I need to get this done I have the part and have tried with a crows foot but no luck. I dont have any type of grinder or a way to create one of those. Thank you
If you are talking about the temp sensor, buy a crows foot flare nut tool that's 18 mm. It is like a crows foot, except it surrounds the hex a little more! Just changed mine recently!
 
#29
If you are talking about the temp sensor, buy a crows foot flare nut tool that's 18 mm. It is like a crows foot, except it surrounds the hex a little more! Just changed mine recently!
Ty for responding...I have a 07 tb so my sensor is smaller and in the hardest place ever to reach..ive actually tried a crows foot w no luck I was hoping to find a slotted 15mm socket to make the ect sensor swap possible...already changed t-stat and still get p0128 code so figure its gotta be the ECT
 
#30
:rant:
Engineers are sado-masochists. Not enough it was hard to reach just above the thermostat (we countered that by replacing it at the same time) but they had to move it to an even harder place. I'd like to kidnap one and make him change the bloody thing!
:rant:
 

BrianF

Well-Known Member
#32
Hey guys, my ACDelco Tstat just arrived. Once my wife is back from her trip, I will put the thing in. Good tips on the install but once question: Is anyone greasing the o-ring? Say silicone grease? or just wiping the surface on the block and bolting her in?

Thanks
 
#34
Is anyone greasing the o-ring? Say silicone grease? or just wiping the surface on the block and bolting her in?
The last time I helped a buddy do this to his Voy, we didn't grease the o-ring, but we did apply a tiny bit of RTV just to keep the ring in the channel. First 2 attempts to put the tstat in, the ring would slip off before we could seat it to screw the bolts in. :twocents:
 

mntegra01

Well-Known Member
#35
Just another tip here for the T-stat replacement.

  1. GO through the wheel well with long extensions
  2. Make a mark on housing and hose with paint pen to get the clocking of the hose to housing right
  3. fold a piece of paper up and place it between one edge of the bolt and the socket, makes for a tight snug fit that won't fall out while trying to reach through the wheel well.
 
#37
I don't even try to get the hose or clamp off the housing until i fish it all out the top where I can work with it. I apply a little silicone grease on the hose to housing fit, so that I can easily adjust the clocking while lining up the bolt holes, yet still have a good seal. I also use about a 30" 1/4 drive extension (pretty much only made for a 4.2 t-stat job), with a swivel socket. And I too use the paper trick wedged between bolt and socket to keep the bolt there until threads are started. No hands or fingers are fitting in there, but that is without alternator or belt removal.
 

BrianF

Well-Known Member
#38
I finally got to it a few days back. Due to the smoke from BC's forest fires wandering in, the temp during the day was bearable. I pulled the alternator and got the top t stat bolt and went in through the wheel well for the hidden bolt. Fished up the t stat and hose from the top as there was no other way I could access the clamp to disconnect the hose. They had it clocked on backwards. I scribed the hose with the t stat bend (which really helped on reassembly) and popped it back in.

I think the hardest part was that hidden alternator bolt. Due to clearance from the alternator itself I had to start with a deep socket with the ratchet into the fan and then switch to a stubby so that the ratchet did not get pinched. All in all took 3 hours for set up, R&R, clean up and test. After I got the system burped I took it for a goo test drive. Vehicle warms up faster, and holds above 90C on the highway, idling etc according to my scanner. It would dip to 89C when the t stat opened. No leaks and I drained the rad so I got another 6 or so liters of fresh coolant into the thing.

So glad this is done, thanks for the help gents!!!
 

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