Toyota Prius overheating problems

Filed Oct 30, 2026 · Engine · IN

The front exhaust pipe assembly (heat exchanger) on my 2016 Toyota Prius leaked engine coolant internally into the exhaust system. Toyota has documented this condition in Technical Service Bulletin T-SB-0135-19 ("Low Coolant, MIL ON DTC P148F00, and/or Poor Heater Performance") for 2016-2019 Prius vehicles and released a redesigned replacement part (17410-37D40). In [October 2026], at about [97,000] miles, I found the engine coolant reservoir was emptying about every night (nearly a full reservoir) with no external leak. A shop pressure test found no leak. Coolant collected inside the tailpipe after the car sat overnight, and white steam came intermittently from the exhaust while driving. The car stored code P148F00. On XXX a Toyota dealer ([DEALER NAME], [XXX]) confirmed coolant leaking from the front exhaust pipe heat exchanger, per T-SB-0135-19, repair order #[RO NUMBER], and quoted $1,870 to replace the front exhaust pipe with the updated part. My concern is that a vehicle losing coolant this fast can run low without warning and overheat while driving, which can cause engine damage or loss of power, and the white steam from the exhaust may reduce visibility for drivers behind. I also worry that coolant entering the exhaust damages the catalytic converter. The car has been serviced regularly, and the leak was not caused by an accident or impact. Toyota covered this repair under its emissions warranty for 8 years/80,000 miles, but my car is past that and Toyota has declined goodwill coverage (Toyota case #XXX). I'm reporting this so the federal safety agency can see that the failure is happening in vehicles outside that warranty period and can evaluate whether it is a safety defect. Vehicle: 2016 Toyota Prius, VIN [XXX] Component: Engine and engine cooling / exhaust system Crash: No. Fire: No. Injuries: No. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Oct 2, 2026 · Engine · MD

I am writing to inform you about a very dangerous situation that occurred to me in June 2026 and that could pose a significant safety risk to other drivers who own 2016-17-18-19 Toyota Prius cars. The risk stems from a defective part (the catalytic converter) that Toyota Corporation knew about in 2019 but failed to notify owners of those models.   Instead of issuing a recall and replacing the defective part, Toyota chose instead to issue a nationwide alert to their mechanics (Technical Service Bulletin (TSB)—0135-19, issued on 9/27/19). Through the TSB, Toyota extended the warranty to 8 years or 80,000 miles for the part. However, Toyota never notified the car owners of this potentially dangerous situation. In my case, the defective catalytic converter failed, causing overheating and destroying my engine, costing me $ 7,454.55 to replace it and other out-of-pocket expenses totaling approximately $ 8,000.  I am seeking your help in getting Toyota Corporation to take responsibility for this matter and with the repair damage to my car. Toyota’s defective part caused this damage, and it failed to notify me of the potential dangers.  In addition, other Toyota Prius owners should be alerted to the serious safety risk to them if the defective catalytic converter fails and causes serious damage to their car. It can also cause an accident while driving. In my case, I was driving in the middle lane on 95N at 60 miles per hour when the car stalled, which could have caused a catastrophic accident. Fortunately, I was able to coast to the shoulder and then call for help.

Filed Sep 22, 2026 · Engine · NJ

Coolant leak into the engine, confirmed by the Toyota servicing center. This may be a common problem with the Toyota Prius, causing early engine failure from a design defect.

Filed Aug 26, 2026 · Engine · CA

Coolant is leaking into the catalytic converter. This seems to be a common issue. Toyota issued a technical service bulletin on XXX covering this exactly. Some 2016–2019 Prius and 2017–2019 Prius Prime vehicles may exhibit low coolant level, MIL on with DTC P148F00, and/or poor heater performance due to coolant leakage at the front exhaust pipe heat exchanger. The front exhaust pipe with heat exchanger assembly has been updated. The repair is listed as a 1.5-hour remove-and-replace of the front exhaust pipe assembly, and the diagnostic procedure involves unbolting the rear exhaust pipe from the front pipe at the mating flange when everything is cold and inspecting for coolant leakage into the exhaust from the heat exchanger. The full TSB is on the federal safety agency's site: [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Jul 6, 2026 · Acceleration, Engine · IL

Unknown. There were a multitude of codes that appeared on the diagnostics causing problems with engine. The temperature, brake, tire sensor lights are all on. The cruise control is not working. White smoke emitting from tail pipe and engine. Main engine coolant leaking. Car overheating rapidly.

Filed Jun 26, 2026 · Engine · 188,000 miles · CA

The contact owns a 2018 Toyota Prius. The contact stated that while driving at an undisclosed speed, the engine constantly overheated. An unidentified warning light was flashing on the instrument panel. An independent mechanic inspected the vehicle and became aware that the coolant reservoir was empty. One month later, the same failure reoccurred. A second independent mechanic inspected the vehicle, and the coolant reservoir was empty. The vehicle was taken to a dealer. The dealer diagnosed the vehicle with a coolant leak into the head gasket. The dealer advisor referenced a customer satisfaction program as the cause of the failure; however, the vehicle was over the mileage limit for the program. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 188,000.

Filed May 19, 2026 · Engine, Fuel system · PA

The catalytic converter heat exchanger failed internally, causing coolant to leak into the exhaust system. Symptoms included white smoke from exhaust and coolant loss with no visible ground leak. This is a documented factory defect per Toyota Technical Service Bulletin T-SB-0135-19 affecting 2016-2019 Prius models. Toyota has denied warranty coverage despite the vehicle was originally bought & spent its entire prior operational life registered in New York, a state covered under Toyota's full 15-year/150,000-mile emissions warranty. Defect was confirmed by an authorized Toyota dealership, in PA. Vehicle had approximately 83,104 miles at time of diagnosis. Manufacturer denied coverage and is forcing the customer (me) to pay a huge amount for this very well known & defective case. MOST IMPORTANTLY ITS dangerous and unsafe for all the cars our there too, since it is very well known that at a certain point this will happen, but despite TOYOTA never sent a RECALL. Due to this, engine light goes on & off, refrigerant is flammable and leaks in the exhaust pipe happens with this specific case, which ultimately could catch on fire, while the vehicle is moving or stalling. Lots of white smoke comes out of the car that directly impact the environmental aspects, and above all, people owning such vehicle, will be running into this issue, which will 100% put the safety of owner and anyone close in proximity to their vehicle at RISK. PLEASE ADD RECALL WITHOUT CAP for ALL SUCH TOYATA PRIUS due to flammable refrigerant leak inside the car engine components, and proven via strong white smoke coming out of exhaust that has the potentially to put the entire car on fire, specifically.

Filed Dec 20, 2025 · NY

In 2025 I decided to clean the hybrid battery fan. I removed the side panels and found that the fan to battery duct had never been installed. I am the original owner and no one had ever removed the inside panels or had reason to remove the duct. This has likely resulted in the overheated battery which now needs replacing even though I have only 161,000 miles on this car which I have always maintained without fail regarding oil changes and other maintenance tasks.

Filed Aug 4, 2025 · Fuel system · GA

Found coolant leak from heat exchanger into exhaust pipe. Looks like, T-SB-0135-19.

Filed Jun 17, 2025 · Engine · 95,000 miles · GA

The contact owns a 2019 Toyota Prius. The contact stated there was a coolant leak and the coolant level was low. There was no indication of coolant on the ground. The check engine and engine HOT warning lights were illuminated. The contact stated that the failure was related to TSB: 0135-19. The vehicle was taken to the local dealer where it was diagnosed that there was a coolant leak in the front exhaust pipe heat exchanger. The parts to repair the vehicle were on backorder. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 95,000.