I’ve got a 2017 Prius with around 350,000 miles on it. I’ve been driving it about 3 hours a day since it was new, and here’s the maintenance history so far: Replaced the brake pads twice. Replaced the left rear wheel bearing assembly twice and the right rear bearing once. Recently had to replace the water pump after it failed about 3 months ago. Reconditioned the hybrid battery 4 months ago using a 4-channel RC battery charger. It’s been working fine since, but if it fails again, I’ll probably just buy a refurbished one to save time. Earlier this year, I replaced the spark plugs and coil packs, likely because they were fouled by a coolant leak. Speaking of the coolant leak, I’ve been adding about 8 oz +/- of coolant daily. There’s no coolant in the oil, but an exhaust gas test shows exhaust gases in the coolant tank. I suspect the EGR cooler might be the culprit, but the head gasket is probably on its last legs, too. I plan to replace both soon, along with the timing chain. Other upcoming repairs include replacing the right front control arm and both ball joints. This car has definitely been through a lot, but it’s still running strong for now!
This is a 4th gen Prius, not a Prius v, which ostensibly is a gen 3, with the same engine and EGR system? I was kinda wondering why your laundry list did not include occasional EGR cleanouts, and/or head gasket replacement.
I never had a problem with egr. I assume because it's mostly highway miles. never had an issue with egr. I've done all the work myself to save money. if it isnt broke or throwing a code it isn't fixed. this will be my first headgasket replacement. as a. correction I have 301000 miles not 380 as I stated above.
Keep an eye on your normal operating temperature. Head gaskets usually doesn't blow unless the engine is running hot - hotter than normal 185-210F. Your over-temperature lamp comes on at 248F. So your car can actually be running hot without you knowing it. As far as I know; the car's ECU software doesn't store engine over temperatures; just sensor malfunctions or what it thinks is sensor malfunction. Both coolants needs to be replaced, engine & inverter. Do a litmus test to make sure they haven't gone acidic. Bypass the exhaust gas heat exchanger to see if that takes care of your coolant usage. The gen4's aren't known for blowing head gaskets, but your on the higher mileage side than most. The heat exhanger leak is a know issue for 2016-2018 model years. You should replace brake fluid and ATF - I do this every 100K miles. I don't believe in life-time fluids. I believe in planned preventive maintenance to side-step major repair bills - cheap insurance.... Hope this helps... Good Luck....
Gen 3 (2010~2015 in the hatchback version) has the EGR clogging and blown head gaskets. Gen 4 EGR is redesigned, problem-free. Toyota basically used gen 3 production cars to test the design, instead of doing it right. Gen 4 (2016~2022) does have an issue with coolant leaks in the Exhaust Heat Recovery system (EHR, similar acronym ), and if left unchecked long enough, can lead to coolant starvation, which can also blow head gaskets. Seems like it was due to a bad batch, and only effects a portion of the earlier years, maybe 2017~2019. It's prudent to keep an eye on the coolant level in the reservoir. There is a warranty extension on the defect, but the part (includes Cat) is expensive, and "oddly" perennially in short-supply. Plus, dealerships tend to develop amnesia about the warranty extension (Toyota corporate doesn't pay as well?). There's a work-around, to bypass the EHR system; dealerships will likely refuse to do, since it "defeats a pollution control".
