2018 Mazda CX-9 engine problems

“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…”

“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…”

“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.”

“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.”

“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.”

“My 2018 Mazda CX-9 experienced catastrophic engine damage after a radiator failure allowed coolant to enter the engine. The vehicle provided no dashboard warning, overheating alert, or coolant warning before the failure occurred. Modern vehicles are designed to alert drivers to overheating or cooling system failures. The lack of warning prevented me from addressing the issue and resulted in catastrophic engine damage. I believe this represents a potential safety defect in the vehicle’s cooling system monitoring and warning system.”