2021 Hyundai Sonata Engine Problems

Your car's exhaust heat recovery system failed, causing about 9 gallons of engine coolant to leak into the hot exhaust. When you accelerate, this produces massive clouds of white smoke that completely block your view of traffic behind you and prevent other drivers from seeing your brake lights, creating a serious collision risk. The coolant loss also caused your engine to overheat and nearly stall while driving. This is the second time this part has failed, and Hyundai issued a technical service bulletin acknowledging the problem affects 2020-2023 Sonata Hybrids, but no safety recall has been issued. Fixing this requires replacing the exhaust heat recovery system core and possibly the oxygen sensors that were damaged by coolant contamination.

Your car's engine cooling system failed and leaked coolant, which burned off as thick white smoke that blocked visibility behind your vehicle and forced other drivers to slow down or stop. The smoke caused your engine to overheat, forcing you to pull over on an unsafe road after driving less than a mile. Your Hyundai dealership confirmed this was a known issue with 2020-2023 Sonata Hybrids and warned that even after replacement, the problem could happen again. Fixing this will likely involve replacing the EHRS coolant system components and diagnosing why coolant is leaking and burning.

Your engine's heat exchanger may develop a coolant leak that causes coolant to seep into the exhaust system, where it burns away silently — making the problem hard to spot until your coolant level drops significantly. Hyundai has acknowledged this defect in technical service bulletin 23-EM-009H, but the warranty coverage varies by dealer and location, and typically expires before the problem appears. If your car is out of warranty, the dealer may refuse to use the TSB repair parts and instead quote you for a complete system replacement, which can cost around $3,000. The fix involves replacing the faulty heat exchanger or the entire cooling system, depending on warranty coverage.

Your check engine light came on, and diagnostic testing suggested the problem may be related to an open recall on your vehicle. On January 28th, your car suddenly lost power and wouldn't exceed 30 mph on flat roads or 10 mph on hills. The manufacturer is investigating whether this is recall-related, but has confirmed there's no fix available yet and says it's safe to drive. You've been without your car since January 28th while the dealership and manufacturer work on diagnosis, with no loaner vehicle offered and no timeline for resolution.

Your engine started shaking and vibrating severely while driving at 3 AM, and your check engine light came on. After shutting off the engine and restarting it an hour later, your car could only drive very slowly. A diagnostic test found a cylinder 3 misfire, EVAP system errors, and a faulty fuel injector. The fix will likely involve replacing the fuel injector and addressing the misfiring cylinder, possibly including spark plugs and fuel system components.

The contact owns a 2021 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the vehicle lost motive power. Additionally, the Forward Collision Avoidance failed to function as intended. The contact stated that the sensor was braking prematurely. The vehicle was taken to the dealer; however, the failure was not duplicated. The contact stated while driving out of the driveway, the vehicle lost motive power. The vehicle failed to restart. The dealer was contacted and made aware of the failure. The vehicle was not diagnosed or repaired by an independent mechanic or the dealer. The manufacturer was not made aware of the failure. The failure mileage was unknown.

I purchased this vehicle brand new. It is still under factory warranty. It has approximately 14k miles on it. I have followed all recommended maintenance procedures. During a routine maintenance appointment at the dealership (Vancouver Hyundai 6802 NE 40th Street, Vancouver WA 98661) they identified a catastrophic engine failure due to internal component deterioration and the engine needs to be replaced. They have had my vehicle in their possession since [XXX] of this year for a total of 134 days. I have a case number at Hyundai # [XXX]. They have not been helpful in providing any information and as of now, I do not know when they even expect to receive a new engine. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2021 Hyundai Sonata. The contact stated while driving 15 MPH, the contact noticed that the passenger’s side rear seat level had become elevated. The contact stated that his daughter who was seated in the child seat head had started touching the top of the sunroof. The contact became aware of a gasoline odor coming from the engine. The contact also became aware that the vehicle was consuming an abnormal amount of gasoline. There was no warning light illuminated. The vehicle was taken to the dealer however, the diagnostic test result was undisclosed. The dealer was unsure of how to service the vehicle. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 87,000. The VIN was not included.

faulty engine thermostat

I was on the highway going 60 mph then all of a sudden my vehicles rpm's jumped way up to 8 and completely lost power was on I-45 in Conroe thankfully I was in the slow lane. I have attached pictures of my dash so I could get proof this time. I had to wait 7 minutes for the car to do anything. It also burned all of my engine oil. So had to buy oil for my vehicle. I just had my oil change 3 weeks ago. This has happened before on on the frontage road a few months ago. I have claims open with Hyundai Customer Care. I have been stating that my engine makes a clicking noise, it hesitates, and seizes all the time. I have had this problem since March of 2021 and I bought the car in January 2021. I know I am not a part of the engine recall but I should be. I am scared to drive it. Hyundai doesn't care one bit. Well enough is enough I will be getting rid of this death trap. If you are looking at Hyundai's don't waste your time or money.

I have a 2021 Hyundai Sonata SEL with a Smartstream 2.5L engine w/ GDI & MPI. I have have always heard a loud knocking noise coming from my engine since I got the vehicle when in park. When you are accelerating it hesitates and you can hear a knocking noise. I have taken it to the dealership multiple times and they were able to feel and hear what I was talking about but ensured me it was fine. Recently it has been a lot worse. On 10/18/2023 I was getting on to the highway from the feeder. I tried to accelerate to about 50 mph and I heard the same knocking noise and my rpms jumped all the way to the top. Then my car suddenly stopped getting on to the highway. It took it about a minute before I could start driving again. Luckily there was no one behind me because it could've been really bad. I got home and looked under the hood and it looked like oil had sprayed out of the engine. You could to see oil splatter on the fender. No one was hurt thankfully. I have been complaining about the knocking and hesitation while accelerating for almost 2yrs.

The contact owns a 2021 Hyundai Sonata. The contact stated while driving 45 MPH, the vehicle inadvertently lost motive power in the middle of the roadway and failed to restart. The vehicle was pushed to the shoulder of the roadway, where the failure persisted. No warning lights were illuminated. The vehicle was towed to the dealer, who determined that there was no oil in the engine, causing the engine to seize. The vehicle was then towed to another dealer, who confirmed the diagnostic results. The contact stated that an oil change was performed three days prior to the failure. The vehicle was not repaired. The manufacturer was notified of the failure, and a case was opened. The failure mileage was 44,000.

The issue is well known across the DN8 platform, hundreds if not thousands of people have this problem.Car and driver even did an article on a car with this same 2.5L turbo DCT engine having the same problem! The problem is the ITMS or thermostat housing unit. I first experienced this getting on to a highway, I lost all acceleration, the turbo dropped to 0 pSI and I received an engine overheating warning on the dash. After pulling over the car resumed normal driving, but with oil temps running 30-40 degrees higher than normal. Since then, I have had loss of boost and acceleration when passing around cars which has almost caused accidents, oil temps constantly running very high and fans constantly running on full blast even after car is off. I have been to the service center 4 times, and they have failed to "replicate" the issue and stated the fan and oil problem is "normal" which it is not. This problem needs to be addressed before somebody gets seriously hurt due to loss of power unexpectedly while driving. PLEASE help! Thank you for your time.

When attempting to pass other vehicles or under quick acceleration such as an on ramp to the highway, the vehicle will experience a sudden loss of power and oil pressure resulting in a fail safe mode which limits your acceleration and causes a sudden decrease in speed and velocity. The issue results in the oil pressure light illuminating and requires the vehicle to be stopped and completely turned off to reset then once turned back on, the problem is “gone” until a sudden acceleration occurs again, which results in the same issue happening. There is a current recall out for similar models but my vin is not listed. I have approximately 50k miles on the car, and am the first owner.

My 2021 Sonata has 32,000 miles & it broke down in the middle of the road. My safety & my daughters safety were at risk. We could have been hit or killed. There were no warning lights. It had to be towed. Repair shop reports the transmission is no good. This vehicle should not have transmission issues. Hyundai will not even cover a rental car. The dealership can’t even work on it for 1-2 weeks. I work & have kids. I need a vehicle. The car breaking down in the middle of the road with no warning is dangerous.

Oct 12: Engine stalled exiting I95 in Kittery Maine. Engine light flashed but did not stay on. Was able to get to safe place but car would not go more than 15mph. Hampton Huyndai reported mis-fire but stated it cleared on its own. Oct 17th: Engine stalled on highway ramp to I495, nearly causing me to be rear ended by other vehicles. Car would not go more than 15 mph. Engine light stayed on. Towed car to Key Salem Hyundai, defective injectors, warrantee repair. Oct 23rd: Car stalls on I93, was able to take immediate exit and turn engine off. Engine light flashed but did not stay on. Took car in to Salem dealership on Oct 24th, no code found. Oct 25th: Car stalls again on city street. Light stays on, Salem dealership replaces cat. convrtr between Oct 26th through Nov 4th. Nov 9th: Car stalls again on city street. Light stays on, currently in Salem dealership. This is a safety issue, in two cases already this car has nearly gotten me in an accident on the highway. I am seeking arbitration for replacement. I am scared to drive this vehicle. I will have a third invoice pending this next repair.

The contact owns a 2021 Hyundai Sonata. The contact stated that while the vehicle was at an independent mechanic for an oil change, the mechanic diagnosed the vehicle with transmission fluid leaking from the engine. The mechanic informed the contact that the transmission fluid leakage was flammable. The dealer was made aware of the failure but informed the contact that they were backed up with other vehicles and could not diagnose the vehicle for approximately three weeks. The vehicle was not repaired. The manufacturer was made aware of the failure and a case was opened. The failure mileage was 5,600.