2018 Mazda Mazda6 Owner Complaints

The car only has 70k miles on it. The engine started smoking under the hood. Immediately stopped to look. There was oil leaking but I could not see from where. I took it across the street to the Toyota dealership and had them look at it. They explained to me that there was a crack in the cylinder head and oil was leaking everywhere. Potentially causing a fire or even an explosion. The old was leaking all over the exhaust manifold and engine. I had my 2 toddlers in the car not long before this happened. This is extremely unacceptable. Currently Mazda is saying it will be 7200 to replace the engine and that cost is on me. I think that is absolutely absurd being there are only 70k miles on the car and I bought it brand new. I also kept up with all of the required maintenance.

NHTSA ID

11755535

Incident

Aug 7, 2026

Got error message that said "Forward Smart City Brake Support Malfunction" slso fot "smart brake malfunction" while driving. The ac stopped, the car speedometer kept going from 50 to zero. The car died and couldn't open doors, windows. Lost steering while driving. We were able to get off road and restart and fine for 2 weeks. While at still light tonight, the car turned off. Windows were up, couldn't open door, emergency blinkers would not come on. This is very dangerous.

NHTSA ID

11753644

Incident

Jul 29, 2026

Crack in Cylinder Head of engine. Mazda has been sued about this and have issued recalls on turbo engines, but not on non turbo ones though its the same systemic design issue with these engines. Wants me to pay 5-7k out of pocket.

NHTSA ID

11734993

Incident

Apr 25, 2026

My cylinder head is leaking coolant. There is a well known and well documented issue with these cylinder heads cracking due to poor casting. This has become such a big issue that Mazda has even recalled the cylinder heads, BUT, only if the engine is equipped with Turbo. However, this issue is becoming enormous even for non turbo owners and is a huge safety issue as it can lead to overheating, stalling, and further damage to other components. I feel very strongly that it is time for Mazda to take some responsibility and extend the cylinder head recall to the non turbo engines.

NHTSA ID

11733118

Incident

Jun 1, 2025

Car had a coolant leak due to cracked cylinder head that was defective from the factory it was fixed but now the car has engine problems again. Don’t want to keep having these issues in the future

NHTSA ID

11729758

Incident

Apr 4, 2026

System Failure: The Power Train (6-speed Automatic Transmission) suffered a major malfunction, documented by diagnostic codes P0731 (Gear 1 Incorrect Ratio) and P0780 (Shift Error). The vehicle is available for inspection. Safety Risk: The failure caused a sudden loss of propulsion while attempting to accelerate. This created an immediate risk of a rear-end collision and left the vehicle unresponsive in the path of oncoming traffic. The transmission's unpredictable shifting makes the vehicle unsafe to operate. Confirmation: The failure and the P0731 code were officially confirmed by Castle Mazda on March 2, 2026. The manufacturer (Mazda) has been notified but has denied a remedy, despite TSB MC-10160555-0001 addressing this specific internal defect. Warning Symptoms: There was no Check Engine Light or dashboard warning prior to or during the failure. The only warning was an extreme, abnormal mechanical grinding/clunking noise from the transmission. The lack of a malfunction indicator light (MIL) meant I had no electronic warning of a looming mechanical failure while in motion.

NHTSA ID

11728615

Incident

Mar 2, 2026

Per Mazda inspection, the back side of cylinder head #3 has an oil leak which is leaking onto the exhaust manifold. This creates a direct fire hazard as Mazda said they highly recommend not driving it for that reason. The Mazda dealership inspected and confirmed the issue, it in February 2026, with only 74,000 miles on the vehicle.

NHTSA ID

11719756

Incident

Feb 13, 2026

I recently discovered a significant oil leak near the exhaust manifold of my 2018 Mazda 6 (2.5L NA), which has resulted in visible smoke and a burning oil odor. Upon taking the vehicle to the nearest Mazda dealership for a diagnosis, the service department informed me that the vehicle has suffered a cracked cylinder head. An active oil drip is visible behind the engine near the exhaust manifold immediately upon starting the car; consequently, the engine is leaking oil directly onto the exhaust components. This condition not only renders the vehicle inoperable but also presents a significant safety and fire hazard. At the time of this writing, my vehicle has only 46,996 miles and has been meticulously maintained. This mileage is well under the 60,000-mile powertrain threshold and represents a premature failure of a major internal engine component. There are numerous reports on Mazda owner forums describing this identical issue occurring in Mazda 6, CX-5, and CX-9 models. Some owners have even reported instances of minor fires or active burning under the hood due to oil contacting hot engine components. Mazda released Technical Service Bulletin TSB #MC-10241612-0001 (SA-037-23), which includes a redesigned cylinder head for 2018–2020 Mazda 6, 2019 CX-5, and 2016–2020 CX-9 models, demonstrating Mazda’s awareness of this design flaw. While the TSB currently only specifies the 2.5L Turbo engines and not the naturally aspirated variants, there is substantial evidence that this is a widespread defect across these model years, unrelated to owner misuse or vehicle mileage. Mazda should take full responsibility by issuing a formal recall or providing an extended warranty to cover naturally aspirated engines, thereby addressing this problem and preventing further safety risks.

NHTSA ID

11709431

Incident

Dec 23, 2025

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.

NHTSA ID

11694210

Incident

Oct 11, 2025

Was driving then car suddenly shut down and all panel lights turned on. The car would not start after an hour it started but was Perkins when driving. Mechanics were unable to diagnose the issue.

NHTSA ID

11688263

Incident

Jul 25, 2025

Premature caliper failure on front and rear. Ruined rotors at 40k miles, confirmed caliper failure by two service shops. Grinding/squeaking sounds intermittently been happening for since 30,000 miles

NHTSA ID

11663276

Incident

May 6, 2024

The contact owns a 2018 Mazda Mazda6. The contact stated upon taken the vehicle to the dealer for an oil change, the dealer notified the contact of a fuel leak. The dealer diagnosed the vehicle and informed the contact that the top of the fuel tank and bolts connected to the fuel pump were significantly rusted, causing the fuel leak. The dealer determined that the fuel tank and the fuel pump needed to be replaced. The vehicle was repaired. The manufacturer was notified of the failure and informed the contact that no assistance would be provided because the contact had already authorized the dealer to repair the vehicle. The failure mileage was approximately 75,000.

NHTSA ID

11660947

Incident

Mar 26, 2025

Mileage

75,000 mi

Bought used with 47k miles. Two weeks later, took it to my mechanic for an inspection, they found a massive oil leak on the back of the motor. Took it back to the dealership and they diagnosed it as a cracked cylinder head, for which there is a known TSB and warranty extension. Unfortunately, the warranty extension only covers a coolant leak from the cracked cylinder head, not an oil leak. Thankfully, the dealership took care of me but had they not, I was looking at a $7k+ repair on a car I had owned for 2 weeks. In the TSB, Mazda acknowledges that there were both design and manufacturing flaws for the affected model years. In acknowledging the issue, they should have issued a recall for affected vehicles, not a simple warranty extension

NHTSA ID

11659983

Incident

Apr 18, 2025

I am having my brake pads changed at a local mechanic and when changing the pads, the mechanic was unable to change them because the rotors and calipers were rusted and the brake pistons stuck. The previous recall only considered Mazda 6 up to 2013 but my 2018 has had the same problem.

NHTSA ID

11646848

Incident

Mar 5, 2025

Software error/loss of engine power. No warning of this before it happens. The car completely loses power, and stalls or stops in the middle of me driving. This has happened on the freeway and risked my life as well as my husbands, and children. This same issue has been a previous recall and fixed in 2019 for my car, and now it is happening again.

NHTSA ID

11636672

Incident

Jan 14, 2025

Coolant leaks at the cylinder head around the exhaust manifold causing my car to over heat. Also when my thermostat is set to the exact temperature for both sides my driver side blows cold and the passenger side blows hot

NHTSA ID

11634788

Incident

Dec 10, 2023

Driving in traffic and the engine temperature warning appeared on dash. Dealer has confirmed there is a large coolant leak from the cylinder head. Mazda released a technical service bulletin regarding the issue affecting Mazda6, cx-5 and cx-9, but I will have to pay for a head gasket replacement.

NHTSA ID

11634029

Incident

Dec 22, 2024

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.

NHTSA ID

11627463

Incident

Nov 18, 2024

My car has stalled out on me 6 times in traffic and wouldn’t restart for hours. I took it to the Mazda dealership and they told me nothing was wrong but it continues to happen. I need something done as soon as possible

NHTSA ID

11616978

Incident

Sep 28, 2024

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 to drive with it. The problem HAS been confirmed by an independent service center. I got a oil pressure warning sign.

NHTSA ID

11616489

Incident

Sep 11, 2024

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 warning light had also illuminated and the vehicle was eventually towed to the local dealer who was unable to determine the cause of the failure. The vehicle was not yet repaired. The manufacturer was not yet contacted. The failure mileage was 67,000.

NHTSA ID

11607569

Incident

Jul 8, 2024

Mileage

67,000 mi

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 afterward at work (<10 seconds). Schedule for drop off at dealer (if car didn't show signs of overheating first (would have called tow truck). Checked fluid levels in car (was ~1Qt low) and topped it off. Drove to dealer (~30min ride) with no issues whatsoever. When dealer looked at it, they said cylinder was warped and leaking, requiring new engine. A just paid off car, with less than 100k miles on it, now needs a new engine that will cost more than half of what it's worth.

NHTSA ID

11600610

Incident

Jul 8, 2024

On [XXX] I purchased a Mazda 6 at Ocean Mazda in Miami, Florida. The car has 18,700 miles. The reason why the car has only 18K miles it's because out of the 4 years we have owned it, it was not used as much as a result of the COVID pandemic and my daughter attending online classes. I have always done timely maintenance services as required by Mazda at our service dealer Ocean Mazda and have proof of maintenance records to confirm the minor maintenance that have been done, oil change, tire rotation, battery replacement and a recall. This past Saturday [XXX] I took our Mazda for an oil change; and I was informed that a Five Point Inspection showed that the Driver Rear brake caliper and pad needed to be replaced because it was measuring 2% lining compared to the three other calipers which showed a 6% lining. Since the 36 month warranty has expired the cost to replace the caliper is $875.20. I'm a mom simply concerned about the safety of my daughter and have zero knowledge about brake pads and calipers, but one thing that I do know is that I have owned multiple cars during my lifetime and have never had an issue with a caliper going bad and much less at 18K miles. I'm conscious of timely maintenance and take care of the cars I owned to lasts years. I asked my service advisor how is it possible that one caliper could go bad in a span of 2,500 miles when the prior inspection done in August 2023 showed all 4 calipers having a 6% lining as per the service report card? Furthermore, the inspection done recently shows the three remaining calipers at 6%. The answer I received from my advisor was that "calipers can go bad", sometimes due to a FAULTY caliper. A caliper on a car with 18K miles should not go bad unless it is a faulty caliper. Mazda should honor the repair as this is a hazard condition caused by their faulty part. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11582244

Incident

Apr 7, 2024

Start engine when cold and it knocks/ taps from the valve cover very loud, found a tab for valve lifters. Mazda said I’m out of warranty and it would be a 2k fix on a car I just bought second hand. A lot of other drivers have experienced the same issue and have even said it’s a safety issues as when it happens for long enough it could cause the cams to wear down causing the car to stall out in traffic or in a dangerous road situation. Very dangerous imo and should be fixed for free as Mazda admitted that it’s a design flaw of the HLA

NHTSA ID

11581032

Incident

Apr 3, 2024

Noticed slight coolant leak, took car to mechanic, he stated cylinder head was cracked, & causing coolant to spray everywhere. Towed car to dealer. Was given repair estimate of over $11,000, for a new engine. I see a safety bulletin online for my year make & model car. This overheating can apparently cause an engine fire. So far, Mazda seems to be showing negligence & not properly addressing the issue for owners.

NHTSA ID

11581010

Incident

Mar 22, 2024