At a minimum, I'd replace the radiator, especially if the coolant looks like a mix of ATF and coolant. Especially with north of 300k miles.
What does the ATF fluid look like and how is the level?
I agree that a used motor might be a good step, as well.
Does the eCVT in the Prius even have a trans cooler? A quick search is only showing aftermarket options.
STM317 said:Does the eCVT in the Prius even have a trans cooler? A quick search is only showing aftermarket options.
It does not. I'm not sure about the C/Aqua we're discussing here but the regular Prius has a separate cooling loop for the hybrid system. Diagnose this as if it were a normal car with a manual transmission and no cooler.
dj06482 (Forum Supporter) said:What does the ATF fluid look like and how is the level?
The gearbox in these is filled more like a manual transmission or rear differential and doesn't really need to be checked unless there is a leak from one of the axle seals.
red_stapler said:dj06482 (Forum Supporter) said:What does the ATF fluid look like and how is the level?
The gearbox in these is filled more like a manual transmission or rear differential and doesn't really need to be checked unless there is a leak from one of the axle seals.
I learn something every day! I had no idea that the CVT fluid wasn't routed through the radiator. Radiator might still be a good idea at 300k plus, but my theory about the ATF and coolant mixing through the radiator is definitely wrong!
Just thought I'd bring this back up and hopefully...said with caution...put a bow on it. By luck, the Lemons race I worked this weekend had a team where the captain spent over 20 years as a Toyota tech. I learned that the Prius C head gasket is made of three very thin pieces of metal, each with a coating on them. After 320k+ miles, the coating can get etchings in it and/or the metal can start to fatigue. When it gets hot, either a small amount of coolant can sneak through the etchings or the metal itself can deform ever so slightly and cause the same thing. Once the car cools down, the metal goes back into shape and the problem goes away. The true long term solution of course is to replace the head gasket, or the entire engine. However he suggested that before doing that I try using the Toyota specific coolant (red in color). He said it is less viscous than parts store stuff and make be enough to not leak through. It won't last forever, but it could run a really long time with no issue that way. Worth the $40 it cost for a gallon of the stuff....
Yup. Matches all the symptoms. I think it is too late for your particular car for a coolant change to solve the problem, but it is good prevention for the replacement engine.
Yeah, very likely is. I just was happy to at least get an understanding as to why it was so puzzling to figure out.
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