Beginner way to replace thermostat: GMC 3.6 V6 LGX 2016 & above: 2019 Acadia P0128

[@SmokeyA55]

Excellent video replace my thermostat yesterday took about an hour thanks for your help

[@jayhavey1170]

Thanks for the video. I just completed this exact job for a friend. I can't recommend any other modifications outside of what you've shown us. I did replace the new o-ring on the old pipe outside of that everything went perfect. I probably wouldn't have done this job if I didn't come across your detailed video. It saved a ton of money for her. Just a side note I did not replace the o-rings on the bypass tubes for the overflow. We took it for a long test drive and no leaks. Thanks again

[@allanmoore4794]

I have a 2018 GMC Acadia, first P0128 code happened at 35K miles. It has happened 4 more times with 77K. I think its a software fault not a hardware fault. For the past couple months I have had my code reader plugged in with it set on system monitor and ECT 'engine coolant temp' being graphed in real time. So far and of course, haven't seen a fault. I am looking for an interruption of the temp data as it happens. On the last two occurrences as soon as I plug in my reader I am getting reliable temp readings. This code also activates the cooling fans on high, the temp gage is driven to 0 temp and a steer assist message, also AC is inop. Hitting the erase code button immediately makes everything normal again. Thermostats and temp probes are usually quite reliable. There are all kinds of people on KZbin that are having this problem with low milage, very suspect.

[@SmokeyA55]

What was your fix

[@SmokeyA55]

What brand of code reader do you have

[@allanmoore4794]

@@SmokeyA55 I have a Craftsman 47208 scan tool . Not intuitive to use, I had to download and print (a whole printer ink cartridge ) the manual. It does give L/D live data so you can watch data in real time as you drive. After watching the L/D I noticed that my engine water temp was never above 172 and as the days got cooler and I wasn't running the AC I noticed the cooling fan didn't ever come on either. So I went ahead and replaced the thermostat and temp prob e. It took 2 hours and I replaced the spark plugs as well since I was in there already. Not a bad job. You will need a 15mm crows foot to get the probe out and in. You will need a mirror to see the bolt that holds the cross tube on the driver side engine. After the change I now have 190's water temp and the fan comes on at 203'. I also noticed milage from 26.7 to 27.1 after several weeks of driving. So I conclude that the thermostat was opening too much and keeping the engine too cool. I ordered new intake gasket and two bypass o rings from parts geek with my VIN number. All were wrong! I had to go GMC dealer and get proper intake gaskets, mine are individual oval -not a one piece plastic sheet with sealing surfaces, the o rings were way too thick. Good luck,.

[@SmokeyA55]

@@allanmoore4794 thanks for all the info Alan I will go ahead an replace my thermostat also already did temp sensor didn’t fix issue

[@CharlesHarper7596]

I just purchased a used 2018 GMC Acadia with 132,238 miles on it. The Service and maintenance records were clean but into only owning it for two days the same issues you listed above started happening.

[@TheWolfMatt]

Excellent video bud. Thanks for posting. Do you have a full parts breakdown of what you used to replace the thermostat on this 3.6L? Thanks

[@michaelmontoya2437]

Did you have to replace the o rings on the two bypass hoses you removed right before pulling the t stat?

[@stevenlittle8317]

Awesome video brother! I’m afraid it’s juuuuust a touch past my skill level. My rule of thumb is, if I can see exposed pistons, I’ve gone too far! 😳 Anyhow, how much do you think I should expect my local mechanic to charge for this repair? Thanks!

[@Mil-usos]

Great question. It's not uncommon to see between $800 and $1,200 (for the by the book method). Thanks for watching.

[@cheddah75]

What did you end up doing with the big chunk of foam you had to tear out? Just kind of stuff it back in there or…?

[@TheJooshIsLoose]

How bad is it to drive with this issue? Trying to decide if I need to handle it immediately or if I can make plans for later in the week to take care of it. Also would this issue cause the ac to stop blowing cold air or did I just get super unlucky and have two issues hit at the same time? Thanks for the vid!

[@mikaelawilliams3373]

The AC not blowing cold is directly related to this issue

[@allanmoore4794]

Get a code reader with erase feature and just clear the code and all is well. I posted above with my Acadia

[@l37b37]

@@allanmoore4794I just tried this and the OBD wouldn’t clear it

[@Mil-usos]

If the code reader isn't clearing it, the coolant temp sensor may be so far gone, that the code is coming back immediately. Giving the impression the code didn't clear.

[@l37b37]

@@Mil-usos good to know. I just order a new sensor. Hopefully that fixes it and I don’t have to replace the thermostat, save myself $150.

[@gtzrg]

I'm doing the same work on my 2019 blazer, I see that the valves inside engine have a lot of build up, is that normal at 50k miles?

[@lukeWiz44]

it is a direct injection engine, so that’s pretty typical.

[@joevasquez4248]

I didn’t put the foam back in is that a problem?

[@Mil-usos]

Doubt it

[@emadalani1842]

GMC design for colant system very bad they were suppose to make the hose outside the engin front mainfeild so redesign the poition of the thermostat and the temp sensor GMC engineers no mind for repairing

[@mtnpwr]

Don’t just replace the thermostat. Also replace the temperature sensor. The cost of the sensor is minimal if you find out later that the sensor was the problem all along. Sending a false reading to the ECM. Don’t ask me how I know!

[@crystalreprogle6272]

Yes! I bought both to do just that!

[@cfisher2447]

sensor is NEVER the problem when you're dealing with the problem that is solved by replacing the thermostat. Waste of time and money.

[@GerryLobbe-un6wc]

Wow cover the intake holes when working