2018 Mazda Mazda6 Engine Problems

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

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.

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.

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.

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

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.

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. 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.

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.

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.

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

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.

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

Cracked Head , not caused by anything I did.

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.

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.

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.

Just noticed my coolant was leaking underneath my car and i went to mazda to check and it came out being a cracked cylinder the car are driven by my daughter from school to work only and has 68k miles, mazda doesn’t want to fix because supposedly the engine warranty only last until 60k

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.

Took care for routine maintenance to car dealer (Ourisman Mazda Rockville MD). No problems with car. They reported that I had an 'Coolant Leak at the Cylinder Head'. Cost to fix: $6412.47 They reported that it was 'normal wear and tear'. I found a service bulletin from Mazda whereby they admit a manufacturing defect that affected 2.5T engines. They corrected on March 25th, 2021. However, engines prior to this date had this defect. No recalls were created. No warning to owners. My car was within the mileage warranty when they identified the defect (<60k miles and < 5 yrs old). While my car is less than 5 years old, they now identified the leak, but it has over 60k miles. The local dealer said I was out of warranty and there is nothing they could do. I spoke with Mazda North American Operation and reported the Technical Service Bulletin that they put out on 10/15/21 (after they had already identified the problem, re-engineered the engine, and changed the manufacturing line), I also explained what was reported to me by Ourisman Mazda and emailed her all the documents. She reported that she would be getting back to me in 24-48 hrs.