This SA supersedes the previously issued SA(s) listed below. The changes are noted in Red. SA-061/25 12/17/25 DESCRIPTION If you encounter any type of electrical concern (e.g, dead battery, engine no start, DTC(s) stored...), interview the customer before proceeding with normal MGSS diagnosis by asking if any aftermarket devices have been installed. Aftermarket devices may be the cause of the electrical concern. Below are a few examples of unusual electrical concerns caused by aftermarket devices. Examples: 1. Devices connected to the DLC-2 (battery discharge/DTC stored) 2. Devices plugged into the 12V outlet 3. GPS tracking device (engine no start/battery discharge) 4. Dash cam (DTC stored)
full bulletin at NHTSA ↗2018 Mazda CX-9 engine problems
moderate Owners of the 2018 Mazda CX-9 have filed 62 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
62
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2014 CX-9 | 13 |
| 2015 CX-9 | 12 |
| 2016 CX-9 | 49 |
| 2017 CX-9 | 34 |
| 2018 CX-9 (this page) | 62 |
| 2019 CX-9 | 15 |
| 2020 CX-9 | 3 |
| 2021 CX-9 | 18 |
When does it fail?
Of the 62 engine complaints filed for the 2018 Mazda CX-9, here's the actual mileage breakdown — failures cluster heaviest at 50,000-75,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Of the 14 model years of Mazda CX-9 we track for engine problems, this one carries the most owner complaints on file — 62.
Engine accounts for 50% of every owner complaint on file for this vehicle — the dominant problem area across 5 categories tracked.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
This Service Alert supersedes the previously issued SA listed below: The changes are noted in Red. SA-011/24 02/12/24, 06/06/24, 07/29/24 DESCRIPTION Mazda has developed factory recommended scheduled maintenance services that support all major vehicle systems. Mazda recommends dealers follow the scheduled maintenance tables as cited in the vehicle-specific workshop manual or owner's manual. Services performed outside of Mazda's factory scheduled maintenance are not recommended. These services are unnecessary and create unneeded expenses for your customers. SCHEDULED MAINTENANCE Refer to the applicable Workshop Manual or Owner's Manual for vehicle -specific manufacturer scheduled maintenance.
full bulletin at NHTSA ↗This Service Alert supersedes the previously issued M-Tip(s) listed below. The changes are noted in Red text. MT-002/19 09/30/19 and 12/19/19 DESCRIPTION If an engine assembly is replaced after a catastrophic internal mechanical failure, clean the intake manifold internally before installing a replacement engine assembly. If the intake manifold is not cleaned properly, the replacement engine may fail prematurely. Metallic debris from the old engine (with catastrophic internal mechanical failure) may rest inside the intake manifold. When the new engine assembly is installed, debris in the intake manifold will be ingested into the new engine and cause internal damage. Clean the intake manifold
full bulletin at NHTSA ↗This Service Alert supersedes the previously issued SA(s) and TSB(s) listed below: The changes are noted in Red. SA-035/24 05/31/24 DESCRIPTION There is a concern that some water pumps are being replaced that are not faulty, due to signs of a very small coolant leak from the bleed hole. This Service Alert is to inform you about the water pump sealing mechanism and the criteria if replacement is necessary or not. A mechanical seal (A) is used for the water pump. This mechanical seal can seal coolant (B) by sliding a mating ring (C) against a seal ring (D). When the sliding surface temperature of the mechanical seal is more than 248 °F (120 °C) while driving, a small amount of steam (E) is lea
full bulletin at NHTSA ↗Some customer's might state that they notice fluid or oil leaking/dripping on the ground when the vehicle is parked. For this concern, inspect the vehicle for any trace of a fluid or oil leak and use the following examples as a guide to determine if it is severe enough to require a repair, or just to clean the area and monitor it at the next service. Examples of residue or seepage that may not be considered a leak and that may not require repair based on splash shield inspection.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2018 CX-9 experiences cracked cylinder heads at surprisingly low mileage, typically between 55,000 and 90,000 miles, though failures occur as early as 39,000 and as late as 135,000. Mazda has published multiple Technical Service Bulletins (TSB 01-002/23, 01-007/22, 01-013/21, 01-002/21) acknowledging the defect stems from a manufacturing flaw: the cylinder head casting is too thin to withstand the stress of the turbocharger and exhaust manifold weight and vibration.
The leak hides behind the turbo and exhaust manifold, staying invisible until coolant runs dry and the engine overheats. Owners report no warning until the dashboard light comes on—sometimes on the highway with family aboard. Once detected, dealers quote $9,000–$12,000 for full engine replacement; cylinder head replacement alone runs $6,800–$7,200. Mazda has declined most goodwill claims citing mileage limits and claiming the TSB voids warranty coverage. A few owners received partial assistance ($3,000–$4,000), but most are left covering the full bill themselves. Class action litigation is underway; owners across forums describe this as a widespread, well-documented design failure.
Same Mazda CX-9 engine reports on nearby years: 2015 · 2016 · 2017 · 2019 · 2021
Failure modes owners describe
Cracked cylinder head with coolant leak
Cylinder head develops cracks, typically at the back near the exhaust manifold or around bolt holes where the turbocharger attaches. The cracks allow coolant to leak out of the cooling system and, in some cases, into cylinders or the crankcase. Owners report the casting appears too thin to support turbocharger weight and mounting stress. Mazda acknowledges this as a known manufacturing defect in TSBs 01-002/23, 01-007/22, 01-013/21, and 01-002/21.
When: Between 39,000 and 135,000 miles; most commonly reported between 55,000 and 90,000 miles
Symptoms owners cite: Engine overheating warning light on dashboard; Rapid or gradual coolant loss (radiator and overflow tank empty or very low); Sweet smell of coolant inside cabin or from engine; White smoke from exhaust or under hood; Engine temperature gauge spiking to 240–260°F; Rough idle, stalling, or bucking at traffic stops; Loss of engine power; Check engine light (misfire codes); Condensation or puddles under parked vehicle; Vehicle left stranded requiring towing
Codes mentioned: P111A (engine overheated), P0300 (random misfire), P0303 (cylinder 3 misfire)
Repairs/costs cited: Complete engine replacement quoted at $9,000–$12,000 by dealers; cylinder head replacement alone quoted at $6,800–$7,200. One owner paid $7,600 for head replacement; another received $3,101 partial assistance from Mazda on a $7,500 repair. Engines reported on backorder into 2025. One owner's engine was replaced under warranty (April 2022).
Recalls/TSBs owners mention: TSBs issued: 01-002/23, 01-007/22, 01-013/21, 01-002/21. Mazda has denied goodwill coverage citing mileage limits (120,000 miles) and stating TSBs void extended warranty coverage. Some owners report Mazda offered partial financial assistance ($3,101 on $7,500 bill, or unspecified 'financial relief'). Mazda informed one owner the TSB had expired in 2023. Class action lawsuits filed; owners reference widespread problem forums and Reddit discussions.
Unannounced engine overheating during driving
Engine temperature rises unexpectedly during normal driving, particularly on highways. Warning light comes on suddenly with little to no prior symptoms. Owners forced to pull over or find safe stopping point immediately. Coolant leak from cracked cylinder head is the root cause, but leak may go undetected until overheating occurs.
When: Occurs without warning; some owners report coolant smell a day or two prior
Symptoms owners cite: Engine overheating warning light illuminates suddenly on dashboard; Engine temperature gauge spikes rapidly to 240–260°F; Message on instrument cluster: 'Please turn off vehicle as soon as possible, overheating'; Sudden loss of engine power; Potential for seizure or abrupt halt in traffic
Codes mentioned: P111A
Repairs/costs cited: Root cause addressed by cylinder head or engine replacement (see cracked cylinder head failure mode for costs).
Recalls/TSBs owners mention: TSBs acknowledge the issue but lack of proactive owner notification leaves drivers unaware until overheating occurs.
Coolant pollution into crankcase/cylinders
Coolant leaks from the cracked cylinder head into the engine block, cylinders, or crankcase. This contamination fouls the engine oil and can lead to internal corrosion or fuel dilution. One narrative suggests moisture (condensation) pooling inside the engine.
When: Develops as the crack enlarges; detection varies from 39,000 to 88,000 miles
Symptoms owners cite: Low coolant despite visible leak inside engine compartment; Condensation inside engine or on top of engine block when parked; Engine rough running or loss of compression
Repairs/costs cited: Engine replacement required; costs same as cracked head repair ($9,000–$12,000).
Undetectable coolant leak until overheating occurs
Coolant leaks from the back of the cylinder head, hidden behind the exhaust manifold and turbocharger, making visual inspection difficult. Owners may not notice puddles under the car or symptoms until the reservoir is nearly empty and overheating warning appears. Some owners catch the leak by observing low coolant levels during routine checks or noticing sweet smell.
When: Occurs silently over weeks or months; detected at 50,000–88,000 miles
Symptoms owners cite: No visible puddles or warning signs until coolant is critically low; Sweetsmell of coolant in cabin (sometimes present day before overheating); Low coolant in radiator and overflow tank when inspected; No dashboard warning until overheating
Repairs/costs cited: Detection requires proactive coolant level monitoring or dealership inspection. Some owners caught the issue early by regular checking.
Recalls/TSBs owners mention: TSBs recommend inspection but no proactive recall or owner notification issued before symptoms appear.
Synthesized from 62 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 12 most recent
After owning this used vehicle for about 11 months, the engine temperature gauge indicated the car was running hot - about 240 degrees. After inspecting the vehicle at home, we added coolant to the system. This helped maintain engine temperature temporarily, but we noted over the next several weeks that the coolant was dropping rapidly. After inspection by a Mazda dealer, it was concluded that…
Engine coolant leaking due to cracked cylinder head, found by Mazda dealership service inspection and diagnostics. Powertrain warranty only covers this until 80,000 miles, our vehicle is 116,000.
Cracked cylinder head resulting in no heat, leaking coolant and risk of overheating and fire. Crack on backside of cylinder head near exhaust manifold bolts. Weight of exhaust manifold is too much for the cylinder head and results in a Crack around the bolt. Cylinder head was casted too thin at the factory resulting in the head no being able to support the weight of the turbo and exhaust…
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…
Fan is not working and car is overheating when driving in traffic or low speeds - from forums this seems to be a common issue with this make/model and year
My 2018 Mazda CX-9 developed a rapid overheating issue which was determined to be caused by a cracked cylinder head. This was a known issue by Mazda as noted in a technical service bulletin (Mazda TSB 01-013/21). I've been told by Mazda corporate and the Mazda dealership where the car is currently parked that this bulletin means nothing and will they will not cover the cost of repair. My…
coolant leaks at the cylinder head around the exhaust manifold. Caused crack in the head. The Mazda 2.5t engine has this common issue that Mazda knows about. Mazda has a bulletin out but has not issued a recall. Car over heated and I was left stranded. Took car to mechanic who says I need to replace my entire engine.
Coolant leak in the 3rd cylinder, causing the car to overheat and cracking cylinder head, making inoperable.
My vehicle was low on antifreeze. I brought it into the dealer and had them look at it. They told me there was an antifreeze leak inside the engine. I told them, I think there's a service bulletin on it. TSB-01-013-21 And there are updates to it. They told me that the antifreeze leak does not pertain to this service bulletin. I told them, how can that be? When it's an antifreeze leak with an…
We noticed a coolant leak and took vehicle in for service. Told that engine has a Coolant Leak at Cylinder Head [XXX] . 5 year old vehicle, 56k miles. No other warnings. All maintenance has been previously performed as required. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Had engine trouble with your 2018 Mazda CX-9?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2018 Mazda CX-9?
It's a documented issue but not catastrophic. 62 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Based on the 62 complaints filed, engine issues most often appear around 60,770 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2018/Mazda/CX-9.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.