Hi All Recently for last few months im observing constant disappearing of coolant, started basically after replacing old coolant which was originally in the car. Im loosing about 200ml every 6k sometimes 300ml. Nothing noticed in the oil as im doing quite a lot miles every month (6k a month ) no oil in the reservoir. Cant find any leak visible, nothing from the top, took off bottom cover and couldn't see anything. Getting really worried that engine may burn very,very slowly coolant without any visible signs. Any idea what should be checked? Car has atm 95k miles on the clock. Is there any chance that coolant vapors in that amount? Cooland replaced was genuine from Toyota garage but looks not same as previous one, still pinky but not same. Kindest regards Bob
it's usually the exhaust coolant heater. a defect allows the coolant to leak into the exhaust and get burned off, so it's unnoticeable. this is the us tsb:MC-10166037-9999.pdf here's a youtube replacement video:search some people just reroute the coolant exhaust lines:watch
Thanks was just in reading all similar issues and dont know why didn't see it b4 posting. Will do some diagnostic tmr morning, but so far last 3 months dots getting connected together after reading couple posts. Thanks for helping me out. Kindest regards Bob
There's a couple of problems with getting it fixed too: 1. The replacement part is chronically in short supply. Considering it's very expensive, incorporated with the catalytic converter, a skeptical person might think Toyota is intentionally dragging their feet on speeding up production of the part. 2. Dealerships are chronically "ignorant" of the TSB, and of Toyota's offer to foot the bill for repair (if/when they can get the part)., a skeptical person and so on...
The simple diagnostic and fix is to bypass the exhaust heat recirculating system. Usually some heater hose and clamps. Secure the exhaust flow thermostatic lever in the full flow position. USA TSB
Also, dealerships typically won't do the bypass, because it defeats a pollution control device. Again, if Toyota would get in gear, talk to the legislators who make the rules, argue that due to the problem being so frequent, and replacement parts being in "short supply", they could maybe get an exception, to allow dealerships to the bypass till parts supply improves. But then they lose face or soemthing, who knows.
I wish I had known how Toyota had designed the coolant system on Prius when I had the issue on my 2010. I’d still be driving it. I had 358k on it when I finally had to junk it because it overheated when I forgot to refill the system. When it happened to my 2019, I took it to the dealership, which I hate doing, but I didn’t see a post about this known problem. Yes, it can be diverted, it cost me $225 just for them to diagnose the problem, then they wanted $2300 to fix it. I opted to order the parts instead of diverting, cost $960 for parts and $150 for labor at my local shop. I don’t know if I should have done it, but I like the car. 232k on it now. Well maintained. I’ll probably keep it as a second car, since I just purchased a 2024 Prius Prime XSE Premium with the solar panel. I’m charging off my Tesla Powerwalls and don’t use any gas.
