Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2018 GMC Acadia owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2018 GMC Acadia. The contact stated that while driving at an undisclosed speed, the vehicle failed to accelerate while attempting to shift gears. The contact stated that the vehicle jerked and made an abnormal sound, with the check engine warning light illuminated. Additionally, the contact stated there was black and white smoke coming from the rear of the vehicle. The vehicle was taken to the dealer, where it was diagnosed with transmission, cooling system, and fuel system failures. The dealer also determined that the engine was leaking oil. The dealer informed the contact that the vehicle required several repairs. The vehicle was not yet repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 126,000.
The contact owns a 2018 GMC Acadia. The contact stated that while driving at 60 MPH, the reduced engine power message was displayed. The RPM increased to high, and the engine revved. The accelerator pedal was depressed, but the vehicle failed to respond as needed. The contact stated that the failure was related to NHTSA Campaign Number: 18V358000 (Fuel System, Gasoline). The vehicle was taken to the local dealer, where it was determined that the high-pressure fuel pump needed to be replaced. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 98,000.
Sold 2018 GMC Acadia by LEE GMC in auburn. Acadias shift to park was defective, dealership replaced before sale did not disclose, shift to park and transmission malfunctions occurred. I returned Acadia to the dealership several times and they would never properly fix or address my concerns now my vehicle is unsafe to drive. I have documentation to support the claims in my letter, I can send as well if you'd like. Thank you Will send attachment
The vehicle has experienced repeated electrical and engine-related malfunctions, including random engine shutdowns while driving and random no-start conditions. The thermostat and cooling system failed and were replaced in 2024. Multiple sensors have failed. The braking system remains noisy even after brake replacement. The lane detection safety system does not provide audible alerts. The vehicle is currently operational and available for inspection upon request. How was your safety or the safety of others put at risk? The vehicle has randomly shut off while driving on both highways and city roads in Azle, Texas. This occurred while my two children were in the vehicle. When the engine shut off, there was a risk of losing power steering and braking assist, which could have caused an accident, especially at highway speeds and in traffic. …
I get error electric Steering assist reduced or unavailable drive with care at around 84234 miles on my car . Upon looking up problem on Internet it has to do with the Thermostat. I also found where Gm has a bulletin N252508350 which only seems to cover certain vehicles with the same problem. This seems to happen at all different miles driven on vehicles. I don't see how Gm can get away with only fixing certain vehicles with this safety problem when it shuts down the electric steering assist . This problem from what I can find on the internet is common to all years from 2017 up in Acadia with the 3.6L engine . The Thermostats seem to be defective and I feel Gm needs to address this problem for all of these vehicles . Not just for there special bulletin N252508350 which covers some vehicles in 2021with 3.6L engines. …
I have this 2018 Acadia where all of a sudden, at random, the radiator fan runs on high constantly, the AC stops blowing cold air, the thermostat gauge on the dash drops to the C, and the Power Assist is reduced and pops up as a message on the dash as well. Sounds like this may be a common problem among Acadia's. It resets at random and everything appears to be normal for a while. In addition, there are no check engine lights and no codes to check. I have had this happening for over a year and had a dealership service the car but never said mentioned it as a problem. So now that it's out of warranty my and has more frequent occurrences now I''m more aware but now it's out of warranty. It comes up on an Acadia Forum as a common issue. [redacted]
A warning popped up on my dashboard stating "Power steering reduced. Drive with care." multiple times. Whenever the warning popped up, my air conditioning would stop working and my engine fan would run very loud. The warning would go off and back on over the course of a year. This started in the beginning of summer, 2024. On 4/3/25 I took it into an auto mechanic shop and after they looked at this warning, they confirmed that the thermostat has an issue where it gets stuck in the "open" position, therefore the thermostat isn't working properly and my car thinks it's over heating, when it's really not. If my car were to overheat while this thermostat wasn't working properly, my engine could overheat or worse. The thermostat part is being replaced today so after today, it won't be available for inspection upon request.
Seemingly at random a warning will pop up on the driver dashboard "Steering assist is reduced at this time". This will lead to a engine coolant temp reading of 0 degrees, no a/c and reduced steering functionality. Through further investigation the OBD code P0128 tells us it's a faulty Thermostat or Thermostat sensor. Even if you get these parts replaced, the issue still comes back. I've seen these exact complaints at least a thousand times across multiple years of this model/make 2016,2017,2018,2019. This is clearly a manufacturers fault and needs a recall before people get hurt.
The thermostat housing fails and is a known issue which causes the car to overheat and they said it will start of fire or shut down and loss of steering assist. The dealerships know about the issue and GMC does nothing leaving people with large repair bills or inoperable cars. the system won't let me upload my receipts here is the part #12678780 I was told by the dealership this is a known issue and they my emissions warranty only covers the thermostat but not the housing, but that they are 1 piece, playing games.....
The car will frequently but not always fail to shut off when the start/stop button is pushed while in Park. The message "shift to park" come up on the display and a yellow light comes on in the button. I have to restart the engine and it often takes as many as 10 attempts to finally shut off the engine. Between each attempt I have to shift the transmission out of park and back into park. This has been happening for more than a month.
Engine complaints in other Acadia years
Frequently asked questions
How common are engine problems on the 2018 GMC Acadia?
NHTSA has 35 complaints about the engine & cooling of the 2018 GMC Acadia, 9% of the model year's 396 complaints.
Is there a recall for 2018 GMC Acadia engine problems?
No. NHTSA lists no engine & cooling recall for the 2018 GMC Acadia, though it has 2 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2018 GMC Acadia engine problems start?
Half of the complaints with a recorded mileage happened before about 29,000 miles, and 50% before 25,000 miles.
Is it dangerous?
Owners linked 4 crashes, 0 fires and 5 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.