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 Mazda6 engine problems
moderate Owners of the 2018 Mazda Mazda6 have filed 21 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
21
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2014 Mazda6 | 5 |
| 2016 Mazda6 | 3 |
| 2017 Mazda6 | 3 |
| 2018 Mazda6 (this page) | 21 |
| 2021 Mazda6 | 12 |
When does it fail?
Of the 21 engine complaints filed for the 2018 Mazda Mazda6, 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 9 model years of Mazda Mazda6 we track for engine problems, this one carries the most owner complaints on file — 21.
Engine accounts for 39% 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 ↗Subject: TSB 01-001/26 Warranty and Parts Kit Update INCLUDES: Warranty Extension Program - Special Service Program (SSP) D8 Check Engine Light ON with DTC P0126:00, 2018-2025 CX-5, 2019-2023 Mazda3, 2019-2022 CX-3, 2018-2021 Mazda6, 2020-2023 CX-30 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has made a change regarding related parts to TSB 01-001/26 which also impacts Warranty Extension Special Service Program (SSPD8). Parts Ordering and Warranty Claims: Effective March 5, 2026 only the related parts kit PYY2-15-SAY can be ordered and claimed for any repair. The two separate parts PYFB-15-169 and PE13-15-296 can no longer be claimed with repaired dates of March 5, 2026 and later.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners of 2018 Mazda6 models with 2.5L engines—both turbo and non-turbo—consistently report cracked cylinder heads appearing between 50k and 95k miles. The cracks leak coolant and oil, and owners cite a known Mazda TSB (TSB 01-0022/23 and TSB SA-031-21) acknowledging manufacturing and design defects. Repairs run $5,000–$7,000-plus and sometimes involve total engine replacement. Critically, oil leaking onto the hot exhaust manifold creates a fire hazard serious enough that dealers have advised owners not to drive the vehicle.
Mazda has issued extended warranty coverage for turbo engines but refuses to extend the same coverage to non-turbo owners despite identical defects, leaving non-turbo owners out of pocket. One owner discovered the defect at routine maintenance before the mileage-based warranty expired, yet the dealer denied coverage because mileage had crossed 60k.
A second widespread complaint involves hydraulic lash adjusters (HLAs): the engine develops a loud ticking noise on cold start. Owners report Mazda has acknowledged this as a design flaw but offers no recall, instead suggesting owners rev the engine above 3,000 RPM as a workaround.
One owner also reported sudden power loss at highway speeds with check engine light illumination, though the vehicle reset after restarting.
Engine overheating has caused at least one vehicle to require complete engine replacement under warranty at less than 100k miles.
Same Mazda Mazda6 engine reports on nearby years: 2021
Failure modes owners describe
Cracked Cylinder Head with Coolant Leak
Cylinder head develops cracks, typically near the exhaust manifold or on the back side, allowing coolant to leak. Cracks appear in both turbo and non-turbo 2.5L engines and are attributed by owners to poor casting design and manufacturing defects. Multiple owners report Mazda has issued a TSB (TSB 01-0022/23 and TSB SA-031-21) acknowledging the issue for turbo engines but not extending coverage to non-turbo variants despite identical defects.
When: Between 50,400 and 95,000 miles; one case identified at routine maintenance under 60k miles
Symptoms owners cite: Coolant leak underneath vehicle; Engine overheating while driving; Low coolant warning or notification; Vehicle stalling or loss of power; Engine temperature warning on dash; Coolant level dropping between checks
Repairs/costs cited: Repairs cited: $5,000–$7,000+ for cylinder head replacement; one dealer quoted $6,412.47 specifically. In at least one case, dealer advised not driving due to coolant-on-exhaust fire hazard. Some owners report dealership denial of coverage citing mileage exceeding 60k or being out of warranty despite vehicle age under 5 years.
Recalls/TSBs owners mention: Mazda issued TSB 01-0022/23 and TSB SA-031-21 acknowledging design and manufacturing flaws affecting 2.5L engines, with an extended warranty for turbo engines and coolant leaks only. Mazda also acknowledged a manufacturing defect in 2.5T engines corrected on March 25, 2021, with no recall or owner notification at the time. Non-turbo owners report Mazda denies similar coverage, stating the issue is turbo-specific only.
Cracked Cylinder Head with Oil Leak
Cylinder head cracks cause oil seepage, typically from the rear or back side of the head. Oil drips onto the hot exhaust manifold, creating smoke and potential fire hazard. Owners report this is a known defect with a TSB (SA-031-21) but Mazda has not universally extended warranty coverage or issued recalls for non-turbo engines.
When: Between 47,000 and 74,000 miles
Symptoms owners cite: Oil leak visible on or under engine; Smoke or odor from under hood when oil contacts hot exhaust; Low oil level warning light; Oil on exhaust manifold (fire hazard per dealers); Oil consumption between service intervals
Repairs/costs cited: One owner was quoted $7,000+ for repair on a vehicle owned for only 2 weeks. Repairs involve cylinder head replacement or resurfacing. Dealers in some cases advised customers not to drive the vehicle due to fire hazard from oil on exhaust.
Recalls/TSBs owners mention: TSB SA-031-21 acknowledges the issue as a known manufacturing defect. Extended warranty available for some engine variants (turbo), but non-turbo owners report denial of coverage despite identical defects. No recall issued for non-turbo engines.
Hydraulic Lash Adjuster (HLA) Noise and Wear
Engine develops a loud ticking or tapping noise from the valve cover area, particularly when cold or at start-up. Owners attribute this to defective hydraulic lash adjusters (HLAs) and report the issue is widespread in 2018 Mazda6 community. Owners assert Mazda has acknowledged this as a design flaw but refuses recall. One owner reports potential risk of cam wear leading to stalling in traffic.
When: Present from initial ownership (60k+ miles reported); noise occurs randomly
Symptoms owners cite: Loud ticking or tapping from valve cover area on cold start; Noise occurs intermittently and randomly; Noise persists across multiple drive cycles; Mazda advises revving engine above 3,000 RPM to manage noise
Repairs/costs cited: One owner reports Mazda quoted $2,000 to repair HLA system. Owners state Mazda told them to rev the engine above 3,000 RPM as a workaround rather than fix the root cause.
Recalls/TSBs owners mention: Mazda has not issued a recall. Dealership offered conditional fix prior to warranty expiration ('would fix it at the dealer if it would tick while in their possession'), which is impractical given the random nature of the noise. Owners assert Mazda has admitted to a design flaw but refuses to recall or universally cover repairs.
Engine Power Loss and Check Engine Light
Vehicle experiences sudden loss of engine power while accelerating or passing, with check engine warning light illumination. Owner reports the failure is intermittent and resets after restarting the engine, suggesting an electrical or fuel delivery issue rather than mechanical damage.
When: At 67,000 miles
Symptoms owners cite: No acceleration response while pressing accelerator pedal; Loss of automotive power while merging or passing; Check engine warning light illuminates; Vehicle operates normally after engine restart; Failure recurs after brief normal operation
Codes mentioned: Check engine light illuminated (code not specified)
Repairs/costs cited: Vehicle towed to dealer; no diagnosis or repair completed at time of complaint filing.
Recalls/TSBs owners mention: None; owner had not yet contacted manufacturer at time of complaint.
Overheating and Blown Head Gasket
Engine overheats while driving, with dealer diagnosis revealing a blown head gasket or warped cylinder. One owner reports the vehicle exhibited two oil leaks and a blown head gasket, requiring complete engine replacement.
When: Less than 100,000 miles; one case at 80,000 miles
Symptoms owners cite: Engine temperature warning on dashboard; Engine overheating while driving; Coolant level drops (1 quart lost in one case); Loss of driving power on freeway overpass; Multiple instances of overheating
Repairs/costs cited: Dealer diagnosed warped cylinder and blown head gasket requiring complete engine replacement. Cost exceeds 50% of vehicle value (used car purchased at less than 100k miles). One owner paid $6,412.47 for cylinder head repair but experienced overheating again shortly after.
Recalls/TSBs owners mention: None documented for this specific failure mode.
Synthesized from 21 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 7 most recent
Cracked cylinder head near the exhaust manifold. Created a large oil leak. Oil on the exhaust is a fire hazard. After one quart of oil loss a low oil level light comes on. This is a reported problem. One version of the engine I have has a Mazda TSB and an extended warranty. TSB 01-0022/23 A local repair shop has diagnosed the problem.
Cracked cylinder head causing oil leak and possible coolant leak. This is a known issue with this year and model. Mazda is trying to suggest the issue is only for the turbo engine, but the non-turbo engine is also defective, per countless reports online. I have a video from the service technician from the mazda dealership, but it is too big to upload.
Coolant leaking from head, informed by dealer the cylinder head is cracked and the entire engine needs to be replaced. The engine has just hit 80k miles at this point. This issue caused multiple instances of overheating while driving, one of which caused the vehicle to fail to move forward while on an elevated freeway overpass with no shoulder during rush hour. This issue appears to be widespread…
Cracked Cylinder Head. At 50,400 miles. This is far too common of a problem for such a new car with so few miles. I have seen many similar reports online. My mechanic was baffled. This is a $5k cost AT LEAST. Mazda has a history of not covering these defects. And it IS a defect, not a simple wear and tear issue. A cracked cylinder head can eventually lead to engine failure, so it is dangerous…
The contact owns a 2018 Mazda 6. The contact stated that while merging onto a freeway the vehicle did not accelerate while pressing the accelerator pedal, lost automotive power. After turning the engine off and back on the vehicle operated as normal but later while driving approximately 65 MPH the failure had reoccurred while attempting the pass a semi-truck on the freeway. The check engine…
At less than 95,000 miles, the car suddenly started overheating. Coolant level was fine, maybe ever so slightly low (could still see the coolant in tubing and some in reservoir, which was closer to low than full). Replaced ECT sensor, thermostat and water pump which seemed to fix the issue. Drove for 9-10 days with no issues and it started overheating again. I was able to park quickly…
I was driving my car, it overheated. I took it in and was told it needs a new engine. I was told it was not fault of my own why it overheated. It had 2 oil leaks and a blown head gasket.
Had engine trouble with your 2018 Mazda Mazda6?
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 Mazda6?
It's a documented issue but not catastrophic. 21 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 21 complaints filed, engine issues most often appear around 67,000 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/Mazda6.
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.