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Discussion Starter · #1 ·
The other day I my wife told me the CEL was on. I checked the code and it was a P0128, which is thermostat temp below regulating temp. The car isn't running hot so I know the thermostat is stick open. I am trying to find the thermostat to replace it, but it is not in stock anywhere. Does anyone know where I can get a thermostat from? The car is an SLT-1 AWD V6. I have read on a couple other forums that GM discontinued the part. I find it hard to believe they would discontinue a part for a newer model car without a replacement. Any insight or help sourcing this part would be appreciated.
Thanks.
 

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You looking for the thermostat only or housing+thermostat?
 

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... I am trying to find the thermostat to replace it, but it is not in stock anywhere. ... Any insight or help sourcing this part would be appreciated.
It appears you want to DIY the work. Why do that when it's most likely covered under your vehicle's powertrain warranty?
 

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Is the powertrain warranty valid if I bought the car used?
Yes it is. The warranty period is based on original delivery date and mileage. New car warranties of most makes/models have transferred with used car purchases for years.
 

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Can you replace just the thermostat?
That wouldn't resolve the problem with your vehicle. Use "P0128" as the keyword in the forum's search function and read about what others went through to get their vehicles repaired. Be sure the thread applies to the 2nd generation (2017+) Acadia.
 

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The T-stat and housing are one part. Not sure why it would not be available. Maybe a shortage or changed part number?
 

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Discussion Starter · #10 ·
I spoke to a mechanic at GMC and he told me the thermostat is not part of the power train warranty. Can anyone confirm if this is the case or not? I can't find this part in stock anywhere, including ebay, where some people have found it. I can't understand why such a common part like a thermostat is so hard to find.
 

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I spoke to a mechanic at GMC and he told me the thermostat is not part of the power train warranty. Can anyone confirm if this is the case or not? I can't find this part in stock anywhere, including ebay, where some people have found it. I can't understand why such a common part like a thermostat is so hard to find.
Read this thread and Post # 27. The part number is in it and available at a number of sources,

There seems to have been an earlier part number for a two part thermostat assembly which includes and extension pipe. You only need the thermostat and gasket and maybe o-rings for the associated water distribution.

Thermostat Replacement

I'm just puzzled at why these thermostats are failing so early on 2018 and even a 2019 IIRC.
 
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I spoke to a mechanic at GMC and he told me the thermostat is not part of the power train warranty. Can anyone confirm if this is the case or not?...
I would be inclined to differ with the 'mechanic.' Here's a passage of warranty coverage from GM.
The Powertrain Warranty covers repairs due to defects in materials and/or workmanship for components listed below:

ENGINE
All internally lubricated parts, engine oil, cooling hoses and lines. Also included are all actuators and electrical components internal to the engine, cylinder head, block, timing gears, timing chain, timing cover, oil pump/oil pump housing, OHC carriers, valve covers, oil pan, seals, gaskets, turbocharger, supercharger and all internal lubricated parts as well as manifolds, flywheel, water pump, harmonic balancer and engine mount. Timing belts are covered until the first scheduled maintenance interval. Exclusions: Excluded from the powertrain coverage are sensors, wiring, connectors, engine radiator, coolant hoses, coolant, and heater core. Coverage on the engine cooling system begins at the inlet to the water pump and ends with the thermostat housing and/or outlet that attaches to the return hose. Also excluded is the starter motor, entire pressurized fuel system (in-tank fuel pump, pressure lines, fuel rail(s), regulator, injectors, and return line) as well as the Engine/Powertrain Control Module and/or module programming.
 
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Thermostat is definitely covered under powertrain. Take it to a dealer and make them show you otherwise.
 

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OP - Out of curiosity what is your mileage on odometer?
 

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I am having the same issue on my 2018. Dealer telling me it isn't covered by powertrain because in order to access the thermostat housing they have to go through all the parts that aren't covered. I'm not sure how that can even be a reason to negate the warranty but they don't seem to care lot about pushing for GM to cover it. Price is over $1800 to fix it.

My odometer is about 78,000

I haven't been able to find a complete powertrain warranty document to download online to read, does anyone have a link?
 

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I haven't been able to find a complete powertrain warranty document to download online to read, does anyone have a link?
Here's one from the manufacturer: GMC MANUALS AND GUIDES. A warranty document should have been provided with the vehicle when it was purchased. That guide is usually bundled in a folder along with the owners manual and Infotainment guide.
 

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Discussion Starter · #17 ·
To follow-up on this issue. My car is not covered under the powertrain warranty because the car has over 60,000 miles. Apparently in 2016 the powertrain warranty changed from 100000 miles to 60000 miles. So I'm back to doing it myself and I STILL can't find this part anywhere!
 

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To follow-up on this issue. My car is not covered under the powertrain warranty because the car has over 60,000 miles. Apparently in 2016 the powertrain warranty changed from 100000 miles to 60000 miles. So I'm back to doing it myself and I STILL can't find this part anywhere!
This parts sites and others now shows the thermostat without the transfer tube and it can be repaired as long as you get the new o-rings between the two. It can be done as shown in the Youtube video earlier in a post.
Note, you will also need the o-rings and/or the "water outlet" that is also connected to the thermostat junction when replacing the thermostat.

2017 Gmc Acadia SLT Sport Utility 3.6L V6 A/T FWD Thermostat. Outlet. HOUSING. UNIT. Engine - 12678779 | GM Parts Corp, Conway SC

Thermostat Replacement

 

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Discussion Starter · #19 ·
I found the part needed on a website that listed it as in stock. However, today I got an email telling me that the order was cancelled because the part was on national backorder and they were unable to get it. Is there a part number for just the thermostat without the outlet tube, since it looks like that can be reused?
 

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I'm just puzzled at why these thermostats are failing so early on 2018 and even a 2019 IIRC.
Exactly. I just experienced the same thing. Steering Assist disabled, thermostat stops working intermittently... $1300 bill from the dealer in order to fix it, and I'm at 62,000 miles. Seems like a common enough issue, wish there were a recall associated with it!
 
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