2016 Toyota Prius: engine overheating

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 Aug 4, 2025 · Fuel system · GA

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

Filed Mar 13, 2025 · Engine · GA

Water pump failed without warning and caused irreparable damage to the engine ("blown" engine requiring replacement). Vehicle began to stall and not respond to attempted acceleration while traveling on 4 lane divided highway, 55 mph speed limit. One "Maintenance Required" message was received the previous week, but disappeared. This is the same message that appears for routine oil changes. No other warning messages were noted at the time of the incident, no unusual noises, and no smoke or other sign of overheating. Driver was able to steer vehicle to safety, but this failure could result in stranding on a busy, dangerous interstate highway. For such a critical piece of the vehicle (i.e., the water pump), there should be obvious warning message(s) and dedicated monitoring of the equipment.

Filed May 23, 2022 · Engine, Transmission · OR

Overheating light began flashing while driving 5/21/22. Drove to Napa Auto Parts and saw coolant reservoir was empty. Bought anti-freeze and filled reservoir. Upon arrival at destination, reservoir was empty again. Filled it again. Upon the next morning, reservoir was empty again. Took it to an auto-shop which found that the exhaust heat exchanger in my car has failed and is leaking coolant. Please see Applicable technical service bulletin, T-SB 0135-19. While the car is less than 96 months old, it is above 80k miles. I see this issue has been escalated in California, where the warranty is for 96 months and 150k miles. Want to report that the change in miles between states is disappointing. This issue is common and should be handled as a known recall, not just a known issue.

Filed Feb 21, 2022 · CA

The active grille shutter system failed due to debris. There is a bulletin already that references error code P05A072 - active grille shutter stuck open. The code I got was P059F73 - active shutter grille stuck closed. Not sure why it wasn’t included in the original bulletin when the cause and part are the same. This seems to be a known problem with this vehicle that can lead to engine overheating. Bulletin referenced was T-SB-0319-17.