2019 Mazda CX-9Recalls, problems, MPG & safety

“The engine cylinder head developed an internal coolant leak, allowing coolant to enter the combustion chamber. This caused engine overheating and smoke coming from the tailpipe while driving. A dealer performed a coolant pressure test confirming coolant leaking into the combustion chamber, and wet/dry compression testing on all 4 cylinders showed low and inconsistent readings consistent with cylinder head coolant intrusion (Cylinder 1: 105/125 psi, Cylinder 2: 115/125 psi, Cylinder 3: 110/175 psi, Cylinder 4: 160/190 psi). Overheating creates a risk of sudden loss of power and potential engine failure while driving, including on the highway. The problem has been confirmed and diagnosed by an authorized dealer service center, and the manufacturer's technical hotline department reviewed the diagnostic findings directly. Warning symptoms (overheating codes and visible tailpipe smoke) first appeared at the time the vehicle was brought in for diagnosis. The manufacturer has an active technical service bulletin addressing cylinder head coolant leaks on this engine and model, along with a related warranty extension program, but has denied coverage for this repair on…”

“The contact owns a 2019 Mazda CX-9. The contact stated that a State Inspection was performed on the windshield for cracks. The contact stated that while driving in the rain, the front windshield wipers turned on independently with the switch in the off position. The contact was unable to turn off the windshield wipers. The contact pulled over to the side of the road and turned off the vehicle. When the vehicle was restarted, the front windshield wipers had turned off. The contact stated that the failure persisted and worsened. The contact stated that occasionally the windshield wipers failed to turn off. The vehicle was taken to the dealer; however, no cause for the failure was found. The vehicle was not repaired. The contact purchased and replaced a sensor. Upon investigation, the contact became aware that the on and off switch for the front windshield wipers related to the sensor located on the front windshield. The contact stated that the sensor controlled the on and off switch and failed to function as intended. The contact stated that the OEM windshield provided protection against the sensor malfunctioning; however, if the front windshield was replaced…”

“2019 CX-9 GT, 30K miles, in August found coolant leaking under the car. This was 5 months past the warranty (but only 30K miles!). After doing research online, I found this is a massively common issue with all engines from several years encompassing 2019, where the coolant leaks due to a cracked cylinder head. There is a TSB from Mazda, which requires replacement of the engine, once the crack is developed. I immediately called Mazda corporate on 8/15/2024 and opened the case with them. They said they can try to assist, but first I have to take the car to the dealer for diagnosis of the problem. Had to wait 2 weeks, then leave the car, they did a full inspection and confirmed cracked cylinder head. Dealer opened up claim with Mazda (which apparently is separate from the case I made when I called the corporate). I had to go back because Mazda warranty dept. was asking the dealer to prove the engine was overheating, which it hasn't yet, because I kept adding coolant, so the engine never overheated. But the dealer lowered the coolant and had the engine overheat a little bit just to generate the computer code the warranty dept was requiring. This itself was an…”