I have a 2019 Awde that developped coolant leaks through the heat exchanger so I did the bottom side bypass. I am now seeing consistent 10% loss pretty much, in mpg basically from the day I did the bypass. I guess it makes sense because the engine has to run more to get up to the temperature, etc. Combined with this, I had a consistent 8% loss in mpg by going from the OEM tires (Ecopia) to Michelin Defender (Costco special) so overall my current mpg is exactly like how my old Gen2 Prius was when I had that car. Oh well.
Gen 2 was still pretty stingy . I thought Toyota had upgraded the heat exchanger by 2018, sorry to hear it
The good news is that your mileage should rebound a bit as the months start getting warmer. You may want to monitor your ECT, that thermostat may be stuck partially open - causing longer warmup times and engine to run richer for longer period of time. I believe it's a 180F thermostat and should get there between 5-10 minutes of engine operations. Blasting the cabin heater on high may extend this out to 15 minutes, but your probably way below freezing to do that. Isn't NY also on the CARB emissions standard? If they are, you may still be under warranty for that failure. Federal emissions warranty is 8 years or 80K miles. CARB warranty is 15 years or 150K miles. Hope this helps.....
What were you expecting this time of year without the heat exchanger reducing the cars warmup cycle time? add some grille block to help the grille shutters to hold some more heat in the engine bay. And Don't forget to remove it when temps get warmer. It's pretty easy to forget it's there. The slower you drive for the first two miles 20 mph is the sweet spot for my Gen 4 in these temps the sooner the warmup cycle will finish than turn on your heater / defroster and the engine will run another mile or two to get the coolant temp up to where the the engine with shut off once in a while at lower than hwy speeds. But without the heat exchanger the engine is gonna run more often in HV mode when its freezing cold outside.
Drove a rig in the 90's till I slid through an intersection under a just turned red light on black ice. The rig was dead as soon as the brakes locked all 18 wheels. It was a erie feeling. Luckily there were only 3 cars watching this at that intersection and they all waited for me to get the rig out of their way.
I am just about at 160k miles so it’s too far gone. I was also under the impression that 2019 Awde wasn’t specifically mentioned in the TSB so I thought it was in the clear. But I was looking at the coolant daily and luckily noticed it so was just adding it since early November last year. It was just a couple of ounces every other day for a while, but lately it would go from full to low after one day of commute. I thought at first may be the cap, so switched the inverter coolant cap onto the ice coolant side, they are the same caps. It wasn’t that. Then I started seeing a lot of white smoke behind me especially gong up hill while accelerating, so that was basically that. I also was monitoring the coolant temp daily as I drove using an app, and it seemed to be running normally (between 180 to 195F, and it would get up to 180 pretty quickly once I get to the interstate) so it was likely not thermostat or the water pump, I have good heat. After the bypass, coolant level is now rock solid at the full mark, so basically it’s all good now. I did use a silicone U shaped 5/8 inch hose instead of the rubber one because it’s so close to the catalytic converter, just in case. Not sure leaving the original rubber hoses attached when you do the topside bypass, has any issues with the rubber burning or melting from the heat…? I did put a short bolt under spring tension in the exhaust flap actuator part to keep the exhaust on full flow through.
Your mpg should not impacted by a bypassed exhaust heat exchanger IF the Exhaust Flow Control Valve was manually secured open. If not the exhaust is blocked from its normal full flow mode and continues through the more restrictive heat exchanger.
Did you ever giggle the muffler around ? When GasketMasters did the bypass video, he explained pretty much exactly what you described above. He also pushed the muffler around a bit - he thought the sloshing around wouldn't be audible on the video, I could hear the coolant sloshing around inside it.
No, I didn’t investigate fluid in the exhaust, it was like 15F so I was under the car outside as quickly as I can to get done… these things fail at the worst timing for sure.
Have you been in touch with any dealerships? If so what's their response? Do you know if you're within time/miles limit for warranty replacement? My 2 cents: Toyota should the nix the warranty limits, and get responsible about making the replacement part abundant, educating dealerships. But here we are...
If coolant was in the muffer when you did the bypass, it's probably still in there. might want to double check it when it warns up. adding a link to the TSB https://static.nhtsa.gov/odi/tsbs/2019/MC-10166037-9999.pdf and the thread that announced it Sept. 2019 - many thanks @Elektroingenieur TSB: Coolant leakage at front exhaust pipe (Prius & Prius Prime) | PriusChat Notice described in the post linked above "replace with the improved part" ie: front exhaust pipe assembly And since this posts date is Feb 2025 here are the warranty conditions - to reduce possible confusion; APPLICABLE WARRANTY This repair is covered under the Toyota Federal Emission Warranty. This warranty is in effect for 96 months or 80,000 miles, whichever occurs first, from the vehicle’s in-service date. Warranty application is limited to occurrence of the specified condition described in this bulletin. For 2016 and 2017 model year Prius and 2017 – 2019 model year Prius Prime vehicles, sold, registered, and normally operated in California, Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island, and Vermont. The California Emissions Defect and Performance Warranty coverage is 180 months from the date of first use or 150,000 miles (whichever occurs first)
How long ago did you do that and why? For troubleshooting ? Are you talking about this part? 17046-24010 - Toyota Parts Deal toyotapartsdeal.com/oem/toyota~actuator~sub~assy~e~17046-24010.html?vin=&make=Toyota&model=Prius%20AWD-e&year=2019&submodel=&extra1=&extra2=&filter=(8=E;0=ZVW51L-AHXEBA)
Just securing the flap in the straight through position, it’s under spring tension. I put a small bolt in there between the part the actuator pushes on and the metal protective housing just to keep the flap in the straight flow through position which is what one should do I guess. I will get back under when things warm up and may be use some wire or something to tie that up more securely. My guess is, since the pipes from the cat are open now and it gets pretty hot, all remaining coolant in there should just cook off pretty quickly. I think on the warranty info above, it says 2016-2017 model year Prius and 2017-2019 Prius Prime… mine is 2019 Prius Awde and it has 160,000 miles on it so it’s past the warranty period anyways. Oh well.
It would have evaporated in the first good drive. Ensuring the heat exchanger is fully open is important.
