2017 Prius losing engine coolant - 110k miles

DIY an exhaust coolant bypass and see if the coolant leak stops? Dealerships are reportedly refusing to do this, saying it’s illegal or sim. AFAIK there’s nothing detrimental other than slight increase in warm up time, and slight mpg drop.

 

They used a UV dye in the coolant to see leaks?

Slow leaks can be hard to find as the liquid can evaporate off quickly in a hot engine bay. If not just a loose hose connection, the water pump is the next place to check.

 

Could not have been said better. I agree
lots of problems with the heat exchanger.

 

If you're replacing that much coolant every week then something is leaking somewhere. At your mileage you're probably outside the warranty. Bring it to another shop or dealership. Obviously the one you went to didn't know what they were doing. Did they just give up? What was their explanation for the coolant draining like that if they can't find the leak?

 

There's something, a TSB or warranty extension.

 

True but if they're saying it's unrelated to the TSB what can he do?

I might try another Toyota dealership if you have a copy of the TSB show that to them. That missing coolant is going somewhere and if it's being burnt off in the exhaust system it might not show with a visual check with a scope.

If you bring it to another shop and they end up performing the same repair as the TSB recommends then you'll want to submit to be reimbursed by Toyota. I believe they would be required to reimburse you even if it's not at a Toyota dealer, especially if it turns into a recall later. But try with another dealership first. Maybe call Toyota corporate.

 

Take it to another dealer. I don't know how they would scope the leak, since the exhaust heat exchanger is behind the CAT and in front of the muffler - located between your front car seats (underside of your car, of course). The proper procedure is to do a coolant system pressure test. If the system doesn't maintain pressure, you've obviously have a leak somewhere. If it's not dripping on the ground or onto your undercarriage shields - it has to be going out the exhaust pipe or into the oil. Since your oil isn't milky; it has to be going out the exhaust. If the car is running fine; no knocks, misfires, or low compression - by process of elimination the leak is in the exhaust gas heat exhanger. If they need verification; disconnect the exhanger coolant hoses at the heat exchanger; seal one end and perform a pressure test there. If there's a coolant leak, it'll also leak air - even a microscopic crack, not seen by the naked eye should bubble through. The 2017's are notorious for this issue; that's why there's a TSB.

Opps; forgot to mention pin-hole leaks along the seams of the plastic to metal joints of the radiator. This should be obvious to any mechanic that's awake and not "huffing" too much exhaust gases. Just look for dry reddish powder; remains of coolant. Just thought I'd mention this since this dealer was somehow able to "scope" your exhaust gases heat exchanger. Maybe they can work their magic again.....

Hope this helps......

PS. the old glycol based antifreeze has a sweet smell to them when burnt; out the tailpipe. I don't know what the composition of the extended life Toyota antifreeze is; so do this at your own risk. Just an old shade-tree mechanic trick......I normally don't tell people to "huff" their exhaust pipe - DUDE...

 

If it's an external leak, there will be pink residue somewhere. If it's internal, there are tests. Take it to a dealer who knows something about cars.

 

take it to a real shop that specializes in Priuses. dealership mechanics are pretty useless most of the time.

 

Coolant reservoirs go up and down based on the temp of the coolant. Being in July now, you probably have more data points on whether this dragged on for a month. Put a tape on the reservoir and verify in the mornings when it’s cold. Take note on whether you drove your car the previous day. If you have a uv light, you can try shining around the engine bay to see any glowing. There are some various tests that can determine head gasket issue. My experience with dealership was quite different because my car was still under 20k miles. They verified no leaks around my car. They didn’t use a scope at all. They went ahead and stayed the TSB applied and did the change. Every dealership will play the game differently.

 

Yeah his dealer seems not great but I wonder if they saw it as not worth the hassle and blew him off. Your car had low miles and was likely well within warranty and they could pretty much depend on Toyota covering the repair. The dealership the OP went to might have seen the odo and thought Toyota would put up a fight and they'd be out the costs. Plus they could probably get a diagnostic fee out of OP a few times before "solving" his mystery problem. They might get to keep some of those and still get the full reimbursement from Toyota for performing the TSB, and "good will" from OP for graciously waiving the last diagnostic fee...