Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2018 Mazda CX-9 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2018 Mazda CX-9. The contact stated that while driving at various speeds, the engine started overheating within approximately 15 minutes of driving. The contact had to pull over and wait for a while to let the engine cool down before continuing to drive. The contact stated that there was a message that the engine was overheating and to stop driving the vehicle displayed. The vehicle was taken to the dealer where it was diagnosed that coolant was leaking into the cylinders due to a fracture in the cylinder head. The contact was unsure of the cylinders with the failure. The contact was informed that the engine needed to be replaced. The vehicle had not been repaired. The contact found a Technical Service Bulletin regarding the cylinder head failure. …
The contact owns a 2018 Mazda CX-9. The contact stated that while the vehicle was parked, he observed condensation under the vehicle. The vehicle was towed to an independent mechanic where it was diagnosed that the engine needed to be replaced. The vehicle was repaired but the failure persisted. The contact stated that while the vehicle was parked, he observed condensation under the engine compartment and on the top of the engine. The vehicle was taken to an independent mechanic where it was diagnosed that there was a crack in the cylinder head and that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 68,000.
The contact owns a 2018 Mazda CX-9. The contact stated that while the vehicle was parked, he noticed an abnormal odor inside the vehicle. Upon inspecting the vehicle, the contact found a trail of coolant. The vehicle was taken to an independent mechanic, who confirmed that coolant was leaking, and referred the contact to the dealer for a diagnostic test. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 88,080.
I purchased my 2018 Mazda CX-9 Grand Touring CPO with 39k miles and was sold the life time extended powertrain warranty through the dealership. The car now has 74k miles. While sitting idle at the school bus stop in my neighborhood waiting for my daughter the temperature gauge light comes on. I immediately drive home (exactly 0.3 miles) not going over 10mph back home, park call a tow truck company to tow it to the Priority Mazda dealership in Tysons Corner, VA from which I bought it. After a few days the mechanic calls and tells me there is a coolant leak and the repairs for the Cylinder Head should be covered under my lifetime extended warranty. A few days later I get a text message from the service rep that states. …
I own a 2018 Mazda CX - 9 with only 53,300 miles. I noticed something was wrong with my engine and had no idea what the issue was. My car would not shut off immediately when I turned it off and the fan was on super high speed. The day before my appointment with my mechanic, the engine light turned on. I was stuck in a parking lot and a friend suggested I use his car to go buy coolant just in case it was needed. Sure enough, I was completely out of coolant. When my mechanic inspected the car he told me I had a coolant leak and suggested I take it to the dealer as they would know immediately what the problem was. …
Approximately three weeks ago, a message on my dashboard said to pull over immediately. Your car is overheating. I pulled over to a nearby auto shop, which indicated that I was just low on coolant. They topped off the coolant, and everything appeared fine. Two weeks later, I got the same message on the dashboard, saying my car was overheating to pull over immediately. I pulled into a nearby auto parts store and purchased coolant for the vehicle. When I checked the reservoir, it was bone dry. I added coolant and drove the car home. The following day, I checked the reservoir to see if there was still coolant, but it was all gone. I scheduled an appointment with the Mazda dealer to have the car inspected. I also checked the Mazda Forum website to see if other vehicles of my make and model had similar issues since I had never experienced this before. …
I purchased a 2018 Mazda cx9 from a local used car dealer several weeks ago. Check engine light came on after a few weeks for cylinder 3 misfire and there was a steep decline of the vehicle performance (hard start, rough idle, lower mpg, sluggish driving). Took it to Berge Mazda who charged me for diagnostics/spark plugs, and ignition coil. They informed me the next steps were a compression tests, fuel injectors and if that didn't fix the problem then they wanted to strip down the engine to evaluate the cylinder head. At this point I decided to take it to my local mechanic who I trust, he diagnosed a cracked cylinder head. Now I'm stuck with a car I just bought that's unsafe to drive needing a 6-8k repair. Upon further research there is a widespread problem with Mazda's manufacturing of there cylinder heads on certain models (including the 2018 Mazda cx9). …
The cylinder head on this 2018 Mazda CX-9 (Skyactiv-G 2.5T engine) cracked, allowing engine coolant to leak and intermix with engine oil, causing loss of coolant and catastrophic engine failure. The vehicle became undriveable in the first week of November 2025 at approximately 125,019 miles and has remained inoperable since; it was not in a crash and had to be towed. This matches a known, documented defect on Mazda's Skyactiv-G 2.5T engine: coolant leakage at the cylinder head near the exhaust manifold, leading to overheating and engine failure. Mazda issued technical service bulletin(s) addressing cylinder-head cracking and coolant intrusion, revised the cylinder-head casting (a superseding part number), and extended warranty coverage (program CSP11) for this specific concern. This vehicle fell just past the mileage cap of that extension. …
While driving at highway speed in heavy rain the oil light suddenly came on followed within 30 seconds by an urgent need to immediately stop the car due to overheating. There was no radiator fluid left due to the sudden and catastrophic structural failure caused by a known manufacturing defect. Mazda calls it csp-11. They did NOT do a recall even though a situation such as this is clearly life-threatening. They offer an extended warranty to fix the problem fully up to 120,000 miles. Our car has 124,000 miles. Two months ago it would have been fully repaired at no cost but now they want in excess of 11 THOUSAND DOLLARS. …
- My 2018 Mazda CX 9 started stalling and jittering at idle and then eventually during slow driving. - Next day I got a check engine light, took to Mazda service center at the dealership I have been going to for last 6 years since I bought the car. - Service center diagnosed that there was a coolant leak through the cylinder head which seems to have cracked. - Further investigation indicated that this has been identified on many other similar Mazda engines and a Technical Service Bulletin had been issued by Mazda to Dealers. - On probing initially, dealership declined they were aware of any such problem. - The amount of repair for the engine replacement (cylinder head and other parts) is exuberant and is almost half of the value of my car, and is not expected for a low 44,000 miles car. …
Engine complaints in other CX-9 years
Frequently asked questions
How common are engine problems on the 2018 Mazda CX-9?
NHTSA has 78 complaints about the engine & cooling of the 2018 Mazda CX-9, 61% of the model year's 128 complaints.
Is there a recall for 2018 Mazda CX-9 engine problems?
No. NHTSA lists no engine & cooling recall for the 2018 Mazda CX-9, 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 Mazda CX-9 engine problems start?
Half of the complaints with a recorded mileage happened before about 76,000 miles, and 33% before 25,000 miles.
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.