Service Brakes Problems of GMC Terrain - part 2

The car’s brakes hardened on the highway, posing a life-threatening danger, right before the engine died. Following a tow to the dealership’s service center, an initial inspection revealed a broken vacuum pump and broken camshaft. The dealership stated that there was evidence that camshaft debris may be scattered throughout the engine. No further inspection has been done at this time due to the probability of major engine damage and/or potential repairs.

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I am submitting this complaint regarding a serious and dangerous brake failure involving my 2020 GMC Terrain slt with approximately 150,000 miles. While driving, the vehicle suddenly experienced a vacuum pump failure that caused a severe loss of braking ability with no warning beforehand. The brake pedal became extremely hard, and the vehicle would barely stop. This created a very dangerous situation and could have easily resulted in a serious accident. Thankfully, I was not driving at a high speed when the failure occurred, and there were no vehicles directly in front of me at the time. However, only minutes earlier I had been traveling approximately 65–70 mph on the highway. If this brake failure had occurred while driving at highway speeds or in heavy traffic, I truly believe it could have caused a major crash resulting in serious injury or death. What concerns me most is that there was no warning before the brakes failed. No warning lights and no issues with my brakes. The sudden loss of braking power was extremely frightening and created an immediate safety hazard. After researching this issue, I discovered that other GMC and gm vehicle owners have reported similar vacuum pump failures and brake assist problems. I believe this is a significant safety issue that should be investigated further. Drivers should not experience sudden brake failure without warning, especially on a vehicle that otherwise appeared to be operating normally beforehand. I am very thankful no one was injured in my situation, but I am concerned that another driver may not be as fortunate. My vehicle had to be towed to a nearby shop and they suspected it was the vacuum pump failure and the car started smoking badly. So I had it towed to the GMC dealership and they called me today to confirm that was the problem and it also caused damage to the camshaft. This is a known issue with the Terrain and there is currently a class action lawsuit.

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The vacuum pump for the brake system failed catastrophically while driving causing damage to the brake booster and lodging metal debree into the engine components. This happened at less than 100k miles on a 2020 GMC Terrain.

Hard as rock brakes long response time mechanic friend says it’s break booster.

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Brake assist light came on and brake pedal became stiff/hard to push. Vehicle struggled to brake. Replaced brake pads and checked brake fluid. Brakes still inoperable. Check engine light came on for vacuum pump. When replacing pump, metal shards and pieces were falling out when original was removed. Once replacement was installed vehicle began hesitating to start and run.

We just got off the bus thruway and my brakes pedal got hard to press and it was hard to stop car I had to push on brake dry hard to get the car to stop it was jarring and o had to get my some and o to a safe place. Garage said it’s brake assist and he researched there’s is an active law suit against gm bc lots of moses and models have this issue although they claim to know nothing about it.

See all problems of the 2018 GMC Terrain 🔎.

The contact owns a 2018 GMC Terrain denali. The contact stated while the contact's daughter was driving, the brake pedal was depressed, however the vehicle failed to stop as intended. In addition, the contact stated that the brake pedal was unusually hard when depressed. The vehicle was taken to the dealer where the vehicle was purchased. The contact stated that the service brake vacuum pump failed while the vehicle was at the dealer. The vehicle was diagnosed with a failed service brake vacuum pump and a failed engine. The contact was informed that the service brake vacuum pump, the cam shaft and the engine needed to be replaced. The vehicle was repaired. The contact stated that the failure was a known failure of the vehicle. The manufacturer was not made aware of the failure. The failure mileage was approximately 260,000.

Vacuum pump exploded into camshaft and engine area, causing me to lose brakes completely on the highway. Costly repairs to clear out metal shrapnel and replace camshaft.

I was driving 55 miles an hour on an expressway. And suddenly my truck just shut off. The brake became very hard unable to break very scary situation for me and my children. Engine power was reduced and would not start, many errors came up. The vacuum pump failed, which also caused the cam shafts to fail. The vacuum pump exploded into pieces and sent metal into my engine.

Faulty brake vacuum pump!!!! 2018 GMC Terrain @ 119254 miles--- no warning! brakes were hard to press, did not work and I rolled into ditch to prevent an accident. I see hundreds of people with same issue now that I am having to research. This was very scary. I was told it was as a brake booster pressure sensor. But that was not the problem. It is the brake vacuum pump. This is so dangerous. Why is GMC not correcting this issue? this is insane. Gm issued multiple technical service bulletins on vacuum and booster issues starting in 2017. Why hasn't anything been done?.

While driving I received a "service brake assist system" alert and a check engine light. After this happened the brakes were extremely hard to press. I had to put my entire weight on the breaks to stop the car. The brake "assist" feature really is making the brakes functional. We were able to safely get to the side of the road. We found a vacuum pump failed and needed to be replaced. There was no sign that this was failing; it worked, then it didn't.

I am driving a 2019 GMC Terrain slt, and I have a serious concern regarding a recent service experience. On 02/10/2026, I had an oil change and a complete vehicle inspection performed at kunes GMC greenfield, wisconsin. After the service was completed and I returned home, I noticed an unusual noise coming from under the engine hood. I immediately went back to the dealership and informed them of the issue. I was asked to return the following day (02/11) for further inspection. After their investigation, I was informed that the vacuum booster had failed. It appears that this issue was not identified during the original inspection, and I was the one who brought the noise to their attention. From my understanding, vacuum pump/booster issues are common with many 2019 GMC Terrain models. I am surprised that this has not resulted in a recall, especially considering the potential safety risks it poses to me and my family. What concerns me even more is that this issue was not detected during the dealership’s inspection. If it had worsened, it could have led to a serious safety situation. I had to spend $450 today to repair what appears to be a manufacturing-related defect. I respectfully request that this matter be escalated and that my claim for reimbursement be reviewed. I would appreciate your assistance in helping me pursue compensation for this expense.

This is a continuation for NHTSA campaign number 11711615. While an additional NHTSA complaint has been filed for the power train, this focuses specifically on design failures in the braking system. Our vehicle experienced a highway failure of the fuel pump, but due to the nature of a powertrain failure the car could not be put into neutral, only remain in park. The car was stranded in the middle of the road. As a awd vehicle it similarly could not be towed as both wheels were fully locked. Tow informed us that there should be a manual release under the shifting column, however, this design safety feature had been removed in the 2024 iteration. The car was stuck on the road behind a blind turn on a somewhat busy road with vehicles typically traveling between 25-50 mph. The failure of a manual override for neutral and braking is a critical design failure that can lead to major accidents and death in the event of engine or transmission failure. There were no warnings, nor instructions or ability to get the car off the road.

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Vehicle was started for the second time that day on 1/5/26 and the engine light was on. I drove the vehicle to an auto parts store to have them check it with an obd-ii scanner. It had code p050f. I had no idea how serious this issue could be at the time. I made an appt with the GMC dealership and dropped it off the evening of 1/6/26. They said there was a software anomaly in the engine control module and needed to be reprogrammed. I paid the $200 diagnostic fee for them to reprogram it. I learned that this anomaly could have caused my brakes to not work while driving it. I had been driving the vehicle back and forth to work until I dropped it off. This issue could have caused serious harm or death to myself and others. While researching online, I've seen that other vehicles have had safety recalls and additional warranties added for these issues, but my vehicle isn't included in this.

The contact owns a 2020 GMC Terrain. While the contact’s wife was driving approximately 40 mph and attempting to depress the brake pedal to pull into the parking lot of walmart, the braking distance was extended while bringing the vehicle to a complete stop. The driver used excessive force on the brake pedal using both feet. The vehicle was towed to a certified mechanic, who diagnosed the vehicle and determined that the brake vacuum pump had failed. The vacuum pump had fractured where it was connected to the camshaft, causing pieces to enter the engine. The brake vacuum pump and the connector were replaced. The manufacturer was made aware of the failure. The failure mileage was approximately 156,000.

Since August 2024, my brake booster has gone a total of five times each time with the notification on the dash service brake assist. And it just went again as of two days ago. I’ve brought it to firestone where they have replaced it each time with a warranty on the part. I called them yesterday to tell them that it went again and they refused to fix it telling me that they got the part from the dealership and that I would have to take it there so the dealership would have to figure out what’s wrong with it as to why the car is “chewing up” the part. I have young kids and this part has gone five times.

While driving down the interstate a notice popped up on my dash about the brake assist. When I attempted to slow down the vehicle to safely pull over the brake pedal was very hard to push. I was able to slow the vehicle to a complete stop but needing to use both feed and press hard with all my weight. Once the vehicle was parked and shut off I turned it back on to have the check engine light pop up on the dash. I contacted onstar and was towed to a dealership. The brake vacuum pump had broken off at the cam shaft and required extensive repairs. It is my understanding that this is a common occurance and there were previous recalls on the other style Terrains due to the same issue. Yet they used the same part on the newer body style being fully aware of the design flaw.

The contact owns a 2018 GMC Terrain. The contact stated that while driving approximately 30 mph, the brake pedal became extremely difficult to depress, with the message "brake assist" displayed. The vehicle was driven to the shoulder of the roadway and the parking brake was activated, and the vehicle was turned off. The contact stated that the transmission failed to shift into gear, and the vehicle was dragged onto a flatbed truck and towed to the residence. The cause of the failure was not yet determined. The local dealer and manufacturer were notified of the failure, but no assistance was offered. The failure mileage was 132,386.

Failure of the cam driven vacuum pump causing brake failure. Leading to a hard brake pedal which increases risk of a crash. Debris from the broken vacuum pump can fall down into the engine causing a catastrophic failure of the engine needing a replacement. This happens with little to no warning. Warranty companies will not pay to repair the known issue. A recall needs to be issued for this to provide a fix. This is a family SUV and I do not feel safe putting my children in a vehicle that can endanger their lives and safety.

The system that failed was the brakes, the car is availble for inspection. My saftey and others was put at risk due to not having brakes to stop. The problem has been confirmed by a dealer as a master brake cylinder failer the vehicle has been inspected by the dealer. There were warning lamps, message and other symptoms of the problem prior to the failure. They first appearead on December 4 2025.

While driving my brakes failed. I was unable to stop my car, my brake pedal became very stiff and I could not stop my car. There were no warning signs or lights on indicating there were any issues with my car prior to this happening. I had to have my car towed to the dealer. The current estimate is for a vacuum pump failure resulting in camshaft damage. Both need to be replaced. I see other GMC cars were recalled for what appears to be a similar issue. I am lucky no one was injured as this could have very easily resulted in a fatal event. I have never heard of such a thing happening before and am beyond belief that this has occurred. This is the third repair I've had done this year. I have also replaced a booter pipe and valve gasket due to leaking oil. The amount of repairs required in such a short a time seems excessive.

While driving on a main road at around 45mph the vacuum pump that supplies brake fluid to the brakes failed. The car was unable to be stopped and had it not been late in the night I could have crashed into other vehicles on the road or hit someone walking. There was not indication prior to the malfunction and was very sudden. This issue has been observed by the dealer as well as multiple other individuals with the same problem for this make and model of car as well as others by the same manufacturer for similar years of manufacturing. This part has also been shown to break into the engine causing complete engine failure due to lack of a shear pin on the vacuum pump.

My cars breaks failed by a vacuum pump failer and I almost died on the a hill going home.

The contact owns a 2020 GMC Terrain. The contact stated that while driving up the driveway at approximately 10 mph, the brake pedal was depressed but failed to function as intended. The contact used force to depress the brake pedal. When the vehicle came to a stop, there was an abnormal grinding sound coming from the front brakes. The contact stated that the message "power assist brakes" was displayed on the instrument panel. The vehicle was not taken to the dealer or an independent mechanic. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 198,000.

Two problems with this vehicle: 1) transmission occasionally slips on the 2-3 shift which the dealer says he cannot duplicate. Vehicle was brought in four times for this problem. According to the dealer gm corporate has stated the transmission is working within normal parameters, since no codes were found. 2) vehicle auto braking randomly slams on the brakes with nothing in its path. Dealer states turn off system to just alert only not alert and brake. No codes were set. Fortunately no one was behind me as this could have caused me to be rear ended by another vehicle. In both cases it appears that if no codes are set the problem does not exist. Nov. 21, 2025, Feb. 12, 2026, July 09, 2026, Aug. 28, 2026.

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The contact owns a 2018 GMC Terrain. The contact stated that while driving at an undisclosed speed, the vehicle shuddered and failed to come to a stop while the brake pedal was depressed. The check engine warning light was illuminated. The vehicle was taken to a local independent mechanic, where it was diagnosed with a locked brake vacuum pump. The contact was informed that parts of the brake vacuum pump had entered inside the camshaft and valve cover. Several unknown local dealers were contacted. The vehicle was not diagnosed or repaired because there was no recall associated with the VIN. The manufacturer was made aware of the failure. The failure mileage was approximately 183,000.

Vacuum pump went out. It was a recall, previously on older models, but this model needs to.

I filed a complaint with NHTSA on November 3, 2025, about my brake system. Here is another one adding more information. I had to have another brake system part replaced. This time it was the brake booster. Cost $1441. 63 (covered by extended warranty actual cost to me $100. 00. ) so far, I have had the booster sensor replaced twice, the vacuum pump and now the brake booster. I asked the mechanic how many parts related to this system were left to replace? this vehicle has 66,000 miles on parts for the braking system started needed to be replaced at 37,000 miles. The total cost for parts, labor is about $500. That does not include the loss of use for this vehicle which is about 15 days. Taking days off of work about 6 days. This has been a problem for GMC Terrains since 2015; there is still a problem with 2020 model year. Please do something before there is a loss of life due to brake failure.

Check engine light is on took vehicle to dealership 10/13/2023 vacuum booster sensor replaced (37,435 miles) $0 gm covered cost 12/9/2024 brake vacuum pump replaced (56,456 miles) $0 extended warranty 1/8/2025 vacuum booster sensor replaced (57,087 miles) $252. 48 not covered by warranty check engine light is on 10/11/2025 took to dealership. They were unable to find issue light was off, was told that gm had recommended several things that could be the cause of light coming on still could not find issue. Last thing gm and dealership recommended was to replace the battery. Cost $104. 00 check engine light came on 10/25/2025 while returning home from tennessee to michigan, light came on in louisville, ky. Had it scanned, booster sensor was the cause. Called aaa had them replace battery light went off. (as you know that if you do that it reset the computer not surprised light went off drove rest of the way home to michigan) cost of replacement battery $295. 00 check engine light came on again 11/2/2025 my best bet is that it is booster sensor again. Nhtsa and gm need to fix this issue. I have not lost breaking ability yet but the horror story that I've read on this site scars me. What are is NHTSA and gm going to do wait until someone is killed because of this issue !!!!!!!!.

Break assist light comes on and brakes stiffen suddenly with no warning. Happened 6 times now in a 3 year span. Gotten it "fixed" each time but it keeps happening.

When approaching a stop sign, the brake pedal became extremely hard I was unable to stop, and rolled through the intersection avoiding collision. I was able to slow down enough to engage the emergency brake. There are no lights on the dash.

Driving approximately 70mph on interstate. Came to a slight hill, gently applied brake pressure, brakes become hard to apply/would not apply. After diagnostics, found brake vacuum pump with damaged fins.

The contact owns a 2018 GMC Terrain. The contact stated while driving at an undisclosed speed, the air bag and abs warning lights illuminated. The vehicle was taken to auto zone to be diagnosed. The vehicle was diagnosed with air bag failure. The contact was informed that the air bag needed to be replaced. The vehicle was not repaired. The dealer was made aware of the failure; however, the contact was informed that there were no open recalls on the VIN. In addition, the contact was informed that once a recall repair was completed, it would not be performed a second time free of charge. The manufacturer was not made aware of the failure. The failure mileage was approximately 95,100.

On my 2020 GMC Terrain the vacuum pump failed and caused my braking system to go out completely. I had to almost stand up on the brakes to get the car to stop and thankfully I got it come to a stop before smashing into another car. I contacted GMC and while they know this is a ongoing problem and there is a warranty out for this particular problem (150,000 miles or 10 year warranty) I was told it is part/ factory specific and that if it was manufactured in certain facilities or had certain parts that they would cover the cost to fix it but however my vehicle was not covered. This poses a dangerous problem for GMC owners. As soon as the check engine light came on I had absolutely no control over the brakes and it was a miracle it stopped. There was no warning prior to this incident and upon looking up information this seems to be a recurrent problem that GMC needs to address seeing as they say they value their customers.

My 2020 GMC Terrain brakes pump failed causing me to hit the median wall on the highway.