Owners describe multiple brake system failures in the 2017 Acadia, with the most dangerous being sudden loss of brake pedal resistance causing the pedal to sink to the floorboard while the vehicle continues at speed. One owner crashed into a light pole at 2:30 PM in a parking lot and sustained chest injuries from airbag deployment; another's vehicle drifted into an intersection. A third reported the same pedal-to-floor failure persisted after the dealer replaced the brake booster and hose, costing $2,700 on a second repair attempt.
Internal master cylinder failures occur without external leaks, allowing brake fluid to seep into the booster pump. One owner heard a squishing noise from the booster after fluid intrusion; another's vacuum pump fractured and lodged debris in the engine. Low brake fluid warnings appear with no visible leaks.
The Electronic Brake Control Module (EBCM) fails, disabling the parking brake. One owner discovered a recall on similar vehicles days after paying for the "wearable" repair out of warranty.
Unwanted automatic hard braking happens without driver input—dealers confirmed GM issued a bulletin about this phantom braking but withheld documentation from owners. Some owners report the parking brake engaging automatically while driving, locking up the vehicle mid-turn.
Dealers frequently cannot diagnose or replicate these failures, leaving vehicles unrepaired.
Failure modes owners describe
Brake pedal loss of resistance / goes to floor
Pedal suddenly loses firmness and travels to the floorboard without stopping the vehicle. Multiple owners report the pedal sinking without warning during normal driving, low-speed stops, or parking maneuvers. Some incidents resulted in crashes. One owner reported this persisted even after dealership replacement of brake booster and hose. Another reported the master cylinder failed and leaked fluid into the booster.
When: At various mileages: 37,500 (master cylinder failure); 66,000 (loose pedal); intermittent during normal driving
Symptoms owners cite: Brake pedal goes to floor with no resistance; Vehicle does not slow down or stop as expected; Problem occurs intermittently while driving, at traffic lights, and during parking; Owner required two brake pedal pumps to regain braking; Crash into light pole reported; Vehicle drifted into intersection after brake failure
Repairs/costs cited: One owner paid $2,700 for second diagnostic and repair attempt after initial booster and hose replacement failed to resolve the issue. Master cylinder replacement attempted at one dealer; vehicle remained unrepaired pending parts.
Recalls/TSBs owners mention: GMC customer service acknowledged safety issue but claimed brakes out of warranty. District Service Manager referenced PIE 0458 dated 3-22-18 noting 'Brake pedal goes to floor with no external sign of a leak' — indicating prior knowledge. No bulletin issued despite PIE on file.
Master cylinder failure with internal brake fluid leak
Master cylinder fails internally, allowing brake fluid to leak into the brake booster pump without external signs. Owners report low brake fluid warnings with no visible external leaks and brake pedal travel issues. One owner reported squishing noise from the booster indicating fluid intrusion.
When: 37,500 miles; after vehicle sat in garage; at undisclosed mileage for vacuum pump fracture case
Symptoms owners cite: Low brake fluid light illuminates; Brake fluid level drops with no external leaks visible; Brake pedal goes to floorboard; Squishing noise from brake booster when pedal depressed; Brake vacuum pump fractured with debris lodging in engine
Repairs/costs cited: One vehicle diagnosed with master cylinder failure; repair not completed as of complaint filing. Another case involved brake vacuum pump replacement (pump had fractured). One owner refilled brake fluid; level dropped again within 3 days with no visible leaks.
Recalls/TSBs owners mention: Manufacturer notified in one case but did not call back; vehicle remained unrepaired.
Electronic Brake Control Module (EBCM) parking brake failure
EBCM malfunction causes parking brake system to fail and illuminates parking brake dashboard warning light. Owner notes recall on similar vehicles issued around same timeframe but dealership and GMC denied connection, classifying repair as warranty exclusion for wearable part.
When: April 11, 2020; approximately 72,000 miles for one delay-related case
Symptoms owners cite: Parking brake dashboard caution light illuminates; Parking brake no longer engages; Vehicle does not fully turn off with 'Shift in Park' message
Codes mentioned: EBCM module fault
Repairs/costs cited: Repair performed April 14, 2020 at Burdick Chevy GMC Buick but classified as non-warranty wearable part. Owner requested reimbursement without success.
Recalls/TSBs owners mention: Owner notes EBCM module recall on similar vehicles was discovered April 16, 2020, days after repair. Dealership and four GMC representatives denied the parking brake failure was related to the recall or issued a bulletin.
Unwanted automatic braking (phantom braking)
Vehicle applies brakes suddenly and forcefully on its own during normal driving, highway operation, and traffic situations. Behavior includes intermittent hard brake application when no driver input or hazard is present, and application when attempting to move forward in traffic. Dealership confirmed GM issued a bulletin to dealers regarding phantom braking but did not provide documentation to owner.
When: Highway driving; low-speed traffic situations; at railroad crossing (29,000 miles)
Symptoms owners cite: Vehicle slams on brakes without driver input; Brakes apply during normal acceleration in traffic; Happens whenever vehicle perceives another vehicle is too close; Automatic braking applies when owner attempts to slow down; Brakes apply intermittently at railroad crossing while attempting to cross tracks; No warning light illuminated in most cases
Repairs/costs cited: Dealership stated fix was to reboot the vehicle computer. Owner reports no copy of the bulletin was provided.
Recalls/TSBs owners mention: Dealership confirmed GM was aware of phantom braking problem and issued a bulletin to dealers. No bulletin or notice provided to vehicle owners.
Brake pedal delay in stopping
Brake system responds slower than expected when brake pedal is depressed, requiring greater-than-normal pressure and extended stopping distance to bring vehicle to halt.
When: 72,000 miles
Symptoms owners cite: Delay in vehicle stopping when brake pedal depressed; Requires more than normal pressure on brake pedal; Requires more time to stop vehicle
Repairs/costs cited: Parts distribution disconnect noted; repair incomplete pending parts availability.
Recalls/TSBs owners mention: Recall campaign 23V334000 (Air Bags) parts unavailable; manufacturer exceeded reasonable timeframe for repair. Manufacturer not notified of brake delay issue.
Brake pedal physical looseness and excessive travel
Brake pedal becomes very loose with excessive free play and travels nearly to the floorboard during normal braking. Owners report audible screeching sound and pedal not returning to normal position.
When: 66,000 miles
Symptoms owners cite: Brake pedal very loose with excessive free play; Brake pedal travels to floorboard when depressed; Loud screeching sound when brake pedal depressed; No warning light illuminated
Repairs/costs cited: Vehicle taken to dealer but not diagnosed or repaired.
Recalls/TSBs owners mention: Manufacturer not made aware of failure.
Parking brake automatic engagement while driving
Parking brake engages automatically while vehicle is in motion or stopped, causing loss of power and difficulty steering. Brake pedal must be fully depressed to decompress the engaged parking brake.
When: Intermittent, occurring at traffic lights and during turns
Symptoms owners cite: Parking brake automatically engages while driving; Parking brake engages at traffic lights; Parking brake engages mid-turn, locking up vehicle and restricting steering; Vehicle loses power when parking brake engages; Brake pedal very hard to release, requires full depression
Repairs/costs cited: Owner took vehicle to dealership twice; no problem found during diagnostic visits.
Brake lights remaining on after parking
Brake lights fail to turn off after vehicle is parked, draining the battery. Dealer replaced brake parts twice and kept vehicle for one week for safety inspection, but problem recurred.
When: Unknown; recurred by October 14, 2019 (service appointment date)
Symptoms owners cite: Brake lights stay on after vehicle is parked; Battery drained in at least one instance; Problem recurs after dealer repair
Repairs/costs cited: Dealer replaced brake parts twice; kept vehicle one week for safety inspection.
ABS system malfunction
ABS system fault indicator signals problem; dealership diagnoses ABS unit as defective requiring replacement.
When: Unknown
Symptoms owners cite: ABS system indicates a problem
Repairs/costs cited: Dealership advised ABS replacement needed.
Synthesized from 22 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.