Engine And Engine Cooling Problems of Hyundai Sonata - part 1

While driving at highway speeds, the emergency brake system will apply and alert me. It’s happened twice now in the last 3 weeks. I’ve experienced a random loss of power while driving on the highway with no check engine light on the dashboard. Lastly, at lower speeds the car will randomly jerk while accelerating with no lights on the dashboard as well. I’ve gone to the dealership but they wanted to charge me a diagnostics fee to first look over the vehicle, which I don’t feel I should be on the hook for since the issue isn’t user caused.

See all problems of the 2023 Hyundai Sonata 🔎.

Hyundai dealership confirms I am in need of a new engine due to large oil consumption which is a known issue on 2018 Hyundai Sonata engines. Hyundai will not approve repairs because I am the second owner and vehicle is out of the 5 year warranty period. I only have 52k miles on my vehicle.

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I am concerned that the engine may seize or stall without warning while driving, creating a risk of crash, injury, or death. The theta ii engine defect is known to cause engine seizure, stalling, and fire. Hyundai has denied warranty coverage based on mileage and second-owner status — both of which are explicitly prohibited as denial grounds under the settlement — leaving me driving an unsafe vehicle.

See all problems of the 2016 Hyundai Sonata 🔎.

The contact owns a 2019 Hyundai Sonata. The contact stated that while driving 55 mph, the check engine warning light illuminated, and the vehicle went into limp mode. The contact stated that the vehicle failed to accelerate above 58 mph. The contact retrieved dtc: p1326 (knock sensor detection system) at o'reilly auto parts and stated that the knock sensor had previously been replaced. The failure mileage was approximately 90,000.

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One engine valve has lost pressure and is not repairable.

On September 8, 2026, while driving a 2013 Hyundai Sonata limited at highway speed, the check-engine light began flashing and the vehicle suddenly lost power. The vehicle slowed to approximately 40 mph, then approximately 20 mph, before the engine completely shut off. I had to maneuver the vehicle to the side of the highway while surrounding traffic continued traveling at highway speeds. This created a serious risk of a rear-end collision or other accident. The engine would not operate afterward and appears to have seized. The vehicle had approximately 100,000 miles at the time of the incident. There had been no clear warning of an imminent engine failure before the check-engine light began flashing and the vehicle lost power. The vehicle has not yet received a complete diagnostic inspection, so the precise cause of the failure is currently unknown. The vehicle is available for inspection upon request. No crash, fire, or injuries occurred, but the sudden and severe loss of power created an immediate safety hazard.

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Knock sensor has detected a failure. Check engine light is flashing and the car is in limp mode.

The a/c evaporator core and the core seal needs replacing on 2020 Hyundai Sonata. Car is 6 years old. I already have a confirmed diagnosis with a ppm refrigerant leak tester at the condensate drain line the diagnosis is 100% confirmed. The evaporator is leaking heavily—we pulled 274 ppm at the drain tube and 177 ppm inside the cabin behind the glove box so refrigerent has been leaking out of the vents. My wife and I were getting headaches for no reason. Our ac has failed and this problem was discovered as the issue and I am paying out of pocket to fix something that should not have failed and has leaked out refrigerent.

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I am reporting a serious engine failure involving my 2013 Hyundai Sonata. The vehicle's engine was previously inspected by a Hyundai dealership as part of a Hyundai engine recall. I followed Hyundai's instructions and brought the vehicle to the dealership for the required inspection. I was informed that the engine passed the inspection, and an orange marking was placed on the oil dipstick. The Hyundai dealership should have the service record documenting this recall inspection. Many years later, at approximately 120,000 miles, the same engine suddenly failed without warning and became locked/seized. A mechanic attempted to turn the engine and determined that it would not turn. I understand that many years had passed and the vehicle had accumulated additional mileage since the recall inspection. I am not claiming that the previous recall issue necessarily caused the current failure. However, I believe the circumstances warrant investigation because this is the same engine that had previously been inspected under a Hyundai engine recall and determined to have passed the inspection. The vehicle had been routinely maintained. Much of the routine maintenance was performed outside Hyundai dealerships by a mechanic in my family and by me, so the Hyundai dealership service history may not contain all maintenance records. I am concerned that the sudden engine seizure may represent a safety-related engine defect or may potentially be related to the previously recalled engine condition. An unexpected engine seizure can result in a sudden loss of propulsion and create a significant safety risk if it occurs while the vehicle is being driven. I am requesting that NHTSA review this complaint, including the vehicle's recall history and any related complaints or investigations involving the 2013 Hyundai Sonata, and determine whether this failure warrants further investigation. The Hyundai dealership that performed the recall inspection have documentation of that inspection.

I am reporting an unaddressed, critical safety defect involving the theta ii engine in my 2017 Hyundai Sonata. The engine has developed a severe internal metallic knocking noise consistent with connecting rod bearing failure—the exact manufacturing defect associated with Hyundai's major engine recall campaigns (such as recall 198 / campaign 966).

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I had taken my Sonata to mike miller hyndia in peoria,I'll and they agreed to do the recall although they had my vehicle for two weeks. They did not service it and when I picked it up they said I had to drive it till the service engine light come on. I was driving it five days later and heard a loud noise and car started malfunctioning I was stuck in a middle of a intersection and I had to push vehicle off road. I broke my right hand in this process and I have also lost my job I am very concerned why they did not service it after they agreed too and sent me off in it in that condition . . The car is currently parked and unsure what to do with it . .

See all problems of the 2011 Hyundai Sonata 🔎.

The car died while going 70 on a highway with no warning signs. The car completely shut off and will not turn over or move at all.

After receiving the Hyundai service campaign 9c2 update on my 2015 Hyundai Sonata on xxx, I have started having jerky acceleration when the car is first started and am driving. Also, while driving at highway speed (~65 mph)) and I take my foot off the accelerator to coast, the engine rpm drops suddenly, anywhere from 250 rpm to 750 rpm, then recovers abruptly to where it was at prior to the drop (typically around 2000 rpm). The engine rpm also drops while driving at slower speeds and recovers but is not as noticeable as it is at highway speeds. It was not doing this prior to the service campaign. There are no check engine lights or pending codes. I brought it back to the Hyundai dealer and discussed the issue with them on xxx. They acknowledged it was likely due to the service campaign and they did not want to keep the car to look at it and said no damage was being done and it was safe to drive. They said a fix was in the works but did not know how long until it was released and I should receive information in the mail on it. Video link [xxx] information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

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The vehicle suffered an abrupt, internal engine seizure while operating in active traffic at highway speeds. This sudden loss of power created an immediate crash hazard, as the vehicle decelerated rapidly in the travel lane, narrowly avoiding a rear-end collision and putting my family and other motorists at extreme risk. The vehicle was towed immediately to an authorized Hyundai dealership service center where it is currently awaiting the physical recall inspection. Prior to the complete engine failure, there were no warning lights, abnormal gauge readings, dashboard messages, or noticeable performance symptoms. The engine seized completely without warning. The vehicle has an open, uncompleted federal safety recall 162 (NHTSA campaign number: 16v729000) for this exact engine manufacturing defect and bearing failure.

See all problems of the 2014 Hyundai Sonata 🔎.

My Sonata 2016 suddenly lit up the check engine icon, which was blinking. It is available for inspection request, as it's in the shop right now. Added 2 qts of oil just to be safe. Was hoping the light would go away in the morning. It didn't. The car was sputtering and jerking while I was attempting to get where I was going, so I drove a little slower so it wouldn't stall out, which would have caused someone behind me to crash into me if it stopped suddenly. My mechanic said it was engine failure, possibly due to oil burning. Hyundai dealer told me there is no recall for this issue, but my mechanic said there had been. I was never notified of such, and when I called them, they said that there was no recall, and she acted like she had never heard of the problem. I find that amazing, since on your website, there are some 717 claims of the same problem.

My engine was decreasing in speed and shutting off if I brake to slow down on major exressways and local roads. I was advise by my dealership mechanic shop that my engine had a recall and need to have it towed to a Hyundai service dealer for a replacement engine . My engine light on the dashboard had a constant blinking light. My vehicle was inspected camelback Hyundai and a new engine was replaced. The dealership is holding my vehicle hostage demanding I pay 2500. 00 for replacement engine that was a recall. They are threatening to place an abandonment charge against me.

The vehicle experienced a theta ii engine failure at under 57,830 miles while driving on northbound [xxx] near the [xxx] parkway u-turn in [xxx]. The engine made a loud noise and lost power. I was able to coast to the far right side of the u-turn under the bridge. I called hero (austin's emergency roadside assistance). They responded, determined it was not a battery issue, and pushed the vehicle to the southern leisure spa parking lot on the southbound side of the road. The vehicle was then towed. The vehicle is equipped with the ksds (knock sensor detection system) software update, installed as part of Hyundai's remedy for this known defect. Despite ksds being installed, the engine failed due to connecting rod bearing wear, consistent with the documented theta ii defect. A Hyundai dealership confirmed ksds was installed but denied the warranty claim, citing maintenance records. The vehicle is available for inspection upon request. The theta ii engine defect has been the subject of prior NHTSA investigations and Hyundai recalls. This complaint is filed to document another failure of the same defect in a vehicle with the manufacturer's remedy installed. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Vehicle: 2015 Hyundai Sonata VIN: [xxx] mileage: ~85,000 description of the problem: while driving, the vehicle suddenly began producing thick smoke from under the hood without warning. I safely maneuvered to the shoulder to avoid an accident. The engine subsequently seized completely and became inoperable. My mechanic diagnosed this as a known internal manufacturing defect in the theta ii engine (connecting rod bearing failure), a widely documented issue for this model and production year. Oil and coolant levels were confirmed normal with no leaks, ruling out maintenance neglect. I initially paid for an unnecessary starter replacement before this diagnosis was confirmed. This is a serious safety hazard that could cause loss of engine power and control while driving, posing a risk to myself and other drivers on the road. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

The contact owns a 2013 Hyundai Sonata. The contact stated that while driving 40 mph, the vehicle suddenly lost power. The contact was able to coast to the side of the road and turned off the vehicle. The vehicle was unable to restart on the side of the road. The vehicle was towed to a certified mechanic who diagnosed that the engine had seized and needed to be replaced. The vehicle was then towed to the dealer, who confirmed the diagnosis. The dealer asked the contact to provide receipts of past oil changes. After submitting the information to the manufacturer, the request to cover the repair was denied. The vehicle remained with the dealer for a month. The manufacturer was informed of the failure by the dealer. The failure mileage was 52,973.

The contact owns a 2022 Hyundai Sonata. The contact stated that the vehicle was repaired under NHTSA campaign number: 25v796000 (fuel system, gasoline); however, while driving 70 mph and depressing the accelerator pedal, the vehicle decelerated unintendedly. The check engine warning light illuminated. The contact stated that upon depressing the brake pedal, the brakes failed to respond as intended. The manufacturer was notified of the failure and stated that the contact would receive a callback. The failure mileage was 140,000.

See all problems of the 2022 Hyundai Sonata 🔎.

Going down the road driving the car lost power and went in limp mode with no warnings on the dash at all!.

See all problems of the 2021 Hyundai Sonata 🔎.

The contact owns a 2012 Hyundai Sonata. The contact stated that while driving at 30 mph, the check engine warning light illuminated, the engine started knocking, and smoke emitted from under the hood. The contact decelerated to approximately 15 mph and drove to her nearby residence. Upon inspection, the contact observed green fluid under the hood. The vehicle was towed to an independent mechanic, where it was diagnosed that the engine had failed and the head gasket was blown. The mechanic informed the contact that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 100,000.

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Engine locked up, crank bearing failure, found out there is known failures with this problem and Hyundai had a class action suit against them in the past and issued lifetime warranty for this engine due to this problem. Took car to local dealer, clay cooley in sherman TX, they have been great but Hyundai corporate has denied the claim stating lack of maintenance records. Car has 175,000 miles on it, I have only owned it for about 5-6,000 miles. I have changed the oil in it twice myself I was able to prove one of those with a receipt but I don't have the other receipt and have been unable to get it. The dealer has records of oil changes up to 150k miles then I was able to find additional proof of other oil changes through car fax at smaller lube shops. The previous owner before me changed their own oil also and did not keep receipts I reached out to them with no luck. Ultimately there is only about a 10k mile gap of unprovable maintenance, this engine model has a known issue, it did not make it to 175k miles without proper maintenance, I can't control what previous owners did with their receipts but lifetime warranty should be lifetime not only if you can prove every detail from people you can't control.

Component & inspection: vehicle engine suffered connecting rod bearing failure and entered restricted p1326 "limp home mode" (max 2,000 rpm). The vehicle is grounded and available for inspection at bud clary Hyundai in [xxx]. Safety risk: sudden, unexpected loss of power occurred while driving, placing me and other drivers at immediate risk on public roads due to the vehicle's inability to maintain normal traffic speed or safely accelerate. Dealer & corporate confirmation: active p1326 engine code is confirmed. Car has been held for 14 days. The franchise is violating federal settlement rules by explicitly refusing to execute the mandatory, free mechanical bearing clearance test (bct) unless I pay out-of-pocket fees. Inspection & corporate compliance failure: car was brought to the dealer on xxx. The service manager admitted in writing that they are withholding safety diagnostics to protect shop labor hours due to an automated computer flag regarding a clerical title brand discrepancy. Hyundai corporate is actively enabling this violation; my case manager refuses to issue a manual compliance override for the safety test and is violating federal settlement terms by withholding my contractually mandated alternative transportation. Warning lamps & symptoms: flashing check engine light and limp home mode triggered instantly and unexpectedly on xxx. There were zero warning symptoms, messages, or abnormal noises prior to that date information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

I was on [xxx] . I was going 70 mph and then my car just instantly stopped accelerating. The check engine started flashing and I pulled to the side. There was a knocking noise and I just stopped. I called my son to come and get us and then my uncle told it to my house. I have several friends that work on cars and have a a tester. Of course they tested it in that same code came up as if it was the knocking center, so I had another friend come and tested with a different tester with the knocking sensor out his own cylinder three it’s not the knocking center the bearing in the motor is on cylinder two, which that’s what it is. I put my pen. I I put my pin number on the website and it’s showing that my car is affected. No it’s not showing on y’all‘s recall because it’s not something that you’re gonna recall. I have a history of my car motor being fixed every six years if I need to provide that, I will email that I’ve been given the runaround to get my car fixed because it’s not showing up on y’all recall, but it is a recall for the bearing in the motor we could’ve gotten hurt no warning no nothing. I just want to be done right because I’ve had my car service for the last six years and nothing went wrong. I just want y’all to be fair and do right and put that on y’all’s recall, I would hate to take this further but if I have to, I will sincerely [xxx]. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

I bought this car new in 2015, when I was at 97000 miles they had to replace the motor and turbo, I am now at 155844 and they are telling me that basically all 4 cylinders have low compression, cylinder 3 is the worst. They are telling me that this car has to have a new motor. I have not done anything to this vehicle to cause no compression. They want me to pay around 8800. 00 to get this fixed.

Diagnosed 07/20/2026 with catastrophic oil ring failure requiring engine replacement. Engine can stall due to oil degradation/absence of causing uncontrolled vehicle handling and fire. This would put myself and others at risk. It has been diagnosed at dealership. Complaint narrative: the subject vehicle is experiencing its third total engine failure due to an inherent manufacturing and design defect, presenting a severe and repeating highway safety hazard. The original factory engine failed catastrophically in 2015 at 116,440 miles and was replaced under NHTSA recall 15v-568. The second engine failed in 2021 at 244,710 miles and was replaced under NHTSA recall 17v-226. The third engine (the second replacement) has now failed prematurely at 334,935 chassis miles, lasting a mere 90,225 miles. An authorized Hyundai dealership diagnosed a total failure of the oil control rings. This mechanical defect allows engine oil to bypass the pistons directly into the combustion chambers. This causes severe, rapid oil consumption, spark plug fouling, engine stalling, and total loss of motive power at highway speeds without prior dashboard warning illumination. The manufacturer is failing to provide safe, durable remedies for its federally mandated safety recalls (see warranty info magnuson-moss warranty act (15 u. S. C. § 2301 et seq. / breach of implied warranty of merchantability). Instead, they are installing subsequent replacement powerplants that suffer from the exact same structural vulnerabilities and component lifecycle failures. This creates a continuous risk of sudden engine seizure and traffic collisions for consumers.

Since I had service campaign 9c2 completed, the car hesitates to start, does a Mini-lurch upon cold start and runs rough. Two weeks ago, it was put in park, lurched backwards, then died. The starter and battery have been replaced but this has not helped. The car ran fine before this update was done.

The contact owns a 2019 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, smoke started coming from the hood and the vehicle was pulled over into a parking space. While opening the hood, the contact saw that fire was coming from the top of the engine. The contact stated that the fire consumed the front of the vehicle, including the windshield and the dashboard. The smoke coming from the vehicle was dark gray and turned black afterwards. The contact called 911, and the fire department was able to extinguish the fire. There were no injuries reported. A vehicle parked next to the vehicle was damaged by the flames. The contact's vehicle was not inspected or officially deemed a total loss. The vehicle was towed to an independent mechanic where an oil change had been performed prior to the failure. The mechanic stated that there might have been a high-pressure fuel valve on top of the engine that possibly caused a gas leak, which started the fire. The vehicle was not diagnosed or repaired. The dealer was not contacted. The manufacturer was not made aware of the failure. The failure mileage was 172,000.

Driving vehicle at slow speed crossing an intersection and engine completely shut down. The engine has completely seized and needs replaced due to a known recall. I have only owned the vehicle for 7 months. Hyundai is refusing to pay for engine replacement claiming a previous recall prior to me owning the vehicle should have been completed. I only drove the vehicle 1,000 miles in that time at nothing over 50 mph. There was no notification to me about this recall.

The contact owns a 2014 Hyundai Sonata. While the contact's wife was driving 65 mph, the engine seized. The vehicle rolled to the shoulder of the road. The driver attempted to restart the vehicle, and the vehicle started. The contact stated that the accelerator pedal was depressed; however, the vehicle failed to accelerate. The vehicle failed to accelerate above 25 mph, and the engine shuttered. The vehicle was driven to the shoulder of the roadway. The vehicle was towed to the residence. The dealer was contacted by phone and made aware of the failure. The vehicle was towed to the dealer. The dealer requested that the contact provide a fleet email associated with the VIN from enterprise, which was the previous vehicle owner. The manufacturer was contacted by phone but provided no assistance. The failure mileage was 141,000.

I recently had the 9c2 emissions recall update performed on my car, and since the update my car drives like total garbage after a cold start. It hesitates to accelerate, it bucks when trying to accelerate, and it’s to the point the engine is about to stall. I took it back to the Hyundai dealership and they said they are aware of the issue, but there is no fix from Hyundai at this time. This is a major safety concern, as the car barely wants to accelerate after a cold start. Please have Hyundai fix this safety issue.

The lower aluminum engine oil pan developed a structural hairline fracture ("micro-crack") directly along the factory casting ridge adjacent to the drain plug. The component failed without any external impact, road hazard, scraping, or underbody damage. The failure was officially confirmed and documented by eckert Hyundai during a service visit on July 13, 2026 (case #42971835). Following the dealer oil service, the fracture degraded into an active, worsening oil drip that requires a catch tray under the vehicle to capture leaking fluid. The vehicle is currently available for inspection. Safety risk: an active engine oil leak poses a significant safety hazard. Rapid or continuous loss of engine oil can cause sudden oil starvation, severe engine seizure, or total power loss without warning while driving at highway speeds, increasing the risk of a crash. Furthermore, dripping oil contacting hot exhaust or engine components presents a potential fire hazard. Prior symptoms / history: this vehicle has a well-documented history of severe internal engine issues and thermal stress, including excessive oil consumption (running 1. 2 quarts low in 1,127 miles), valve cover gasket failure, and severe drivetrain vibrations from failing front axles. The excessive internal crankcase pressure and thermal stress from these underlying defects contributed directly to the material fatigue and structural failure of this aluminum oil pan.

I am writing to report a direct violation of the theta ii class action settlement terms by Hyundai motor America. This morning , I emailed an executive case manager explicitly explaining that my 2017 Sonata has an active p1326 code, has the 2019 ksds update, and requires a mandatory diagnostic under NHTSA recall 17v226 that cannot be denied due to a salvage title. Instead of replying to my facts, the case manager kathy gave me a hard denial falsely framing my federal recall safety request as a "voluntary goodwill warranty" issue to justify her rejection. Please help me in getting authorization my car with Hyundai dealership in plano TX to run the bearing rod test and get it fixed.

My vehicle while driving, it is jerking and shaking. When I come to a stop, the cars rpms go up and down while the car is shaking. When I pressed the gas pedal to accelerate the car will not accelerate as normal and the car jerks as I’m driving it. The rpms rev up and down without any pressure placed on the gas pedal. The check engine light came on. The miles per hour only allows me to put one digit. I wanted to clarify that the problem is occurring anywhere between 0 mph to 65 mph when these the car jerks and shakes and the rpms go up and down without me pressure on the gas pedal.