Mazda CX-9 overheating problems

Filed Nov 4, 2026 · Engine · 86,000 miles · NJ

The contact owns a 2021 Mazda CX-9. The contact stated that while driving approximately 20 - 25 MPH, the check engine warning light illuminated. The contact used a diagnostic scanner and retrieved DTC: P0303, for a cylinder #3 misfire. The vehicle was taken to a local Mazda dealer to be diagnosed and repaired. The dealer found a coolant leak and performed a system cleaning and replaced the spark plugs and fuel injectors. However, the failure reoccurred. While the contact's wife was driving the vehicle, the check engine warning light illuminated, and the vehicle was towed to the dealer by the insurance company. The contact requested that the dealer inspect the cylinder head gasket and coolant system in his presence. The dealer informed the contact that the repair warranty would be limited to one year or 12,000 miles. The contact also contacted the manufacturer customer service but was not provided any additional assistance. The failure mileage was approximately 86,000.

Filed Oct 31, 2026 · Engine · FL

**the federal safety agency VEHICLE SAFETY COMPLAINT – ENGINE FAILURE AND UNAVAILABLE REPLACEMENT PART** I am filing this complaint regarding serious engine problems with my 2016 Mazda CX-9 equipped with the 2.5L SKYACTIV-G Turbo engine. My vehicle experienced significant engine problems, including overheating, diagnostic trouble codes P0014 (exhaust camshaft timing/VVT system performance) and P0303 (cylinder 3 misfire). Following diagnosis, the cylinder head was found to be cracked, requiring machining and replacement of the timing kit. Despite these extensive repairs and expenses, the vehicle continues to have unresolved engine problems, including rough idling. The vehicle has not been fully repaired because I cannot obtain the exhaust-side Variable Valve Timing (VVT) actuator required to complete the repair. I have been unable to locate this component, and Mazda USA has indicated that the part is not available through its U.S. or Canadian parts network. This leaves me with a vehicle that cannot be properly repaired due to the apparent unavailability of a critical engine component. I find it unacceptable that an essential engine component for a Mazda vehicle cannot be sourced through the manufacturer or its authorized parts network. The situation has resulted in significant financial hardship, prolonged vehicle downtime, and the inability to restore my vehicle to proper operating condition. I am concerned that the underlying engine and VVT-related problems may represent a broader safety and reliability issue affecting other owners of 2016 Mazda CX-9 vehicles equipped with the 2.5L turbocharged engine. I respectfully request that the federal safety agency investigate the reported engine problems, including overheating, cylinder-head cracking, VVT actuator failures, and the availability of replacement components. I also ask that the federal safety agency determine whether these conditions represent a safety defect that warrants further investigation or corrective action by Mazda.

Filed Oct 6, 2026 · Engine · CO

We discovered the problem by accident -- pulled out of our garage and there was a coolant puddle on the garage floor. No dashboard warnings, no overheat messages, no visible symptoms before that. That's what makes this failure mode dangerous: it loses coolant silently, and you find out from a puddle or from an overheat, not from the car telling you. A Mazda dealership confirmed the failure during a multi-point inspection by one of their master technicians (September 2026): coolant leaking from the back of the cylinder head, no signs of coolant and oil mixing, and a scan showing no history of overheating. Their recommendation is cylinder head replacement. The vehicle is available for inspection on request. This exact failure mode is a known design defect on 2016-2020 CX-9s with the 2.5T engine. Mazda itself acknowledged it -- special service program CSP11 ("Coolant Leaks at Cylinder Head Warranty Extension," the federal safety agency doc MC-11011136-0001, issued October 2024). That program extended the powertrain warranty to 10 years / 120,000 miles for precisely this failure, covering vehicles produced before June 2020 -- which includes this one. Here's the part that gets me: my vehicle is in the CSP11 VIN range, and the defect was diagnosed inside the program's 10-year date window. But the odometer is past 120,000 miles, so coverage was denied. The owner notification for CSP11 didn't go out until November 2024 -- to original owners. I bought this vehicle used, and never received that notice, so the extension was effectively invisible to the person actually driving the car as it crossed the mileage threshold. A manufacturer-documented design defect shouldn't lose all coverage on a technicality for used owners. Cause: UNKNOWN. The crack is at the cylinder head stud bolt hole area, matching Mazda's own documentation (TSB 01-002/23). No maintenance schedule prevents a casting crack.

Filed Sep 30, 2026 · Engine · OH

Cracked head cyclinder leaking. Unsafe to drive, coolant can leak into engine if not already. They are aware of it and extended a warranty for the issue in 2024. However people like me, my coolant didn't leak until this year 2026. There have been lawsuits on this issue, but they are still failing to address this issue. They created another part to replace the defected part which costs around $6000-$7000. Yes, took it to a Mazda dealer and confirmed the issue and they can fix but cost would be out of pocket. No warning at all. The only way this was discovered was the smell of the coolant leaking.

Filed Sep 17, 2026 · Engine · 124,000 miles · CT

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. I have spoken to more than 6 people in customer service, 2 supervisors, and they are ADAMANT they will not cover one single penny of repair even though this was not due to wear and tear, but due to a known and recognized manufacturing defect which they have since corrected in newer cars. First, this should have been a full recall since having this happen with no warning is without a doubt life threatening. If an inexperienced teenager had been driving and their engine suddenly seized, they likely would have died, and taken adjacent cars with them. Second, why is this limited extended warranty allowed, it is arbitrary and capricious to say they will fix their mistake up to 120,000 miles but then in an 8-year-old car they will pay nothing? Prior to this there was no advance warning, no fluid leak, and the car had been serviced regularly without any mechanic noticing anything. 3/14/26 repair rear brake pads/rotors 113,896 miles 7/10/26 oil change/tire rotation 123,544 miles 8/7/26 Catastrophic failure due known manufacturing defect csp-11. Brought to Mazda dealer and they confirmed the hole in engine caused by this defect that has an extended warranty. Car still sitting at dealership a month later, now, like a brick, because who has $11,000 in their pocket?

Filed Sep 15, 2026 · Engine · PA

My 2018 Mazda Cx-9 equipped with the skyactiv-g 2.5T developed a serious cylinder-head/cooling-system failure. The vehicle began to lose coolant with no apparent external leak and subsequently displayed and engine -overheating warning. It continued to lose coolant after a flush. The Mazda dealership inspected the vehicle and diagnosed a warped cylinder head; I was also advised that the engine oil was milky, indicating coolant contamination. The affected component is the engine cylinder head/cooling system. This condition created a safety concern because loss of coolant and overheating can lead to severe engine damage or engine failure and potentially leave the vehicle disabled while driven. Mazda has formally documented a cylinder head coolant leak condition in certain 2016-2020 CX-9 2.5T, including cracks around the cylinder head, exhaust manifold area, and states that the cylinder hear/exhaust manifold gasket design was modified to address the condition. Mazda then established customer service program CSP11, extending coverage for the specific cylinder head coolant leak condition to 10 years/120,000 miles, whichever comes first. The dealer has confirmed and inspected my vehicles condition, and Mazda customer experience has also review the matter after I provided the TSB and CSP11 information. Mazda has declined financial assistance because my vehicle falls outside the applicable coverage period and has stated that its decision is final. I am submitting this complaint because I believe this documented cylinder head failure may represent a significant safety/reliability concern for other CX-9 owners, particularly if the condition develops shortly after the 10 year /120, 000 mile coverage limit. I believe and should be made aware of the potential for coolant loss, overheating, and engine damage and that the federal safety agency should review the scope and safety implications of this condition.

Filed Aug 8, 2026 · Engine · IN

I was driving home from work and may car started overheating out of nowhere. I was stuck in traffic and white smoke was exiting my exhaust. I pulled over and all of my coolant leaked out of my car. Took it the shop and they said I had a cracked head and need a whole new engine. I seen that there was a warranty sent out for a problem with an exhaust manifold issue leaking coolant and that is exactly what caused my problem. I contacted Mazda and they said there is nothing they can do. I will have to hire a lawyer and file a class action lawsuit. I never recieved anything from Mazda regarding the issue. They should be paying for my car. I had zero issues until the day it faulted out. I am outraged that I had a great car then something that Mazda knew about cause me an issue.

Filed Jul 15, 2026 · Engine · CA

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. Safety risk: a cracked cylinder head causing coolant loss and engine overheating can produce sudden loss of engine power and overheating if it occurs while driving. No crash, fire, or injury resulted in this case. A formal dealer diagnosis is pending; the failed engine/cylinder head is being preserved and is available for inspection on request.

Filed Jul 10, 2026 · Engine, Transmission · KY

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 basis that the leak is internal rather than external.

Filed Jun 5, 2026 · Engine · NC

My wife was driving the vehicle when the emergency lights started going off. She had to pull over because the car wouldn't run and said it was overheated. All the maintenance has been done to the car. We took it to the dealership and they said it is a cracked head and it is a known issue. They even issued a extended warranty for it. It is TSB 01-002/23. There should be a recall on this not just a partial credit.