2018 Mazda Mazda6 Engine Problems

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

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

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

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

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

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

Mazda has a huge issue with there HLAs hydraulic lash adjusters. I've driven the car for 60k+ miles and it's ticked every since I got the car. And many people in the community also have the issue. And Mazda says it's fine and to rev the car above 3k rpms. This issue needs to be resolved. Before my warranty went up they said they'd fix it at the dealer if it would tick while in there possession. That's just not reasonable the tick happened as random as it gets. Please please for the sake of Mazda and all it's owners make Mazda fix this as a recall. Many people in the US would be the happiest people in the planet not having to hear there 20k$ car tick like a broken old piece of junk. Thank you for listening. Your truly a franticly hopeless hard working america with a half broken car.

NHTSA ID

11578921

Incident

Mar 22, 2024

At 65,000 miles and on time maintenance a head gasket blew.

NHTSA ID

11577033

Incident

Mar 7, 2024

The engine has developed an oil leak that is a known manufacturing defect of Mazda 2.5 litre engines TSB #SA-031-21. The oil drips on the hot exhaust and sends smoke into the cabin and probably could start a fire. Also if the engine runs out of oil, it will cause the car to shut off and stall in traffic.

NHTSA ID

11570493

Incident

Dec 4, 2023

Cracked Head , not caused by anything I did.

NHTSA ID

11563581

Incident

Dec 4, 2023

Was at a drive in window and car turned off and couldn't restart. Windows and lights would work but car wouldn't restart. Could of been driving and would of crashed. Had 3 people family in car. It was 9 pm had to have towed to nearest auto mechanic place 150.00. They are diagnosing and that is 186.00. This is a scary thing and going to BBB and filing a complaint I'm mad as he'll. Have had inspection done on this car 2 months ago and all required services to this car. This was without warning which is horrifying.

NHTSA ID

11560045

Incident

Dec 13, 2023

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 for 2016 and newer Mazda models with the 2.5L turbo engine.

NHTSA ID

11548064

Incident

Sep 29, 2023

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.

NHTSA ID

11530133

Incident

May 14, 2023

Due to design issues, the engine cylinder head became cracked after normal everyday usage. Coolant began to leak badly and car engine became hot while driving.

NHTSA ID

11522138

Incident

Apr 16, 2023