Massive Coolant Leak!!! Please help. (Now $4,000 Engine Repair!!!). Fixed! (Post #48)

is there a puddle where you park?

 

it could be coolant. i depends on how fast you're losing it. at a very slow rate, it might dry or evaporate before puddling. or if it only leaks while running, you could be leaving it on the road.

any way to get it up on a lift and remove the aero panels?

 

you can got to a parts store like o' reily and have them loan you a radiator / coolant pressure test so you know where its leaking or a pressure drop.
A bad thermostat with delay opening will do that too. I had my share of those when I was young. Never again.

 

Codes or temp lights? Clearly you have low coolant probably lower than you think with air or combustion gasses in the coolant system. This is obvious when the heater is delayed. Excessive temp will cause the reservoir cap to release pressure and spray coolant.

Codes would tell you if you had a pump problem or excessive temp causing the cap release. Other possibilities are thermostat or clogging sealer previously used in the system.

A Prius head gasket fail will burn the coolant in the cylinder and replace some of the coolant with combustion gas.

Act quickly or the engine will be ruined.

 

Thermostats rarely fail these days. The water pump does fail but normally will code. You must have codes if the temp lights come up. Typical auto supply scanners are rarely good on hybrids. The check engine, car with ! sign or the triangle light are typical.

Temp lights intermittently means it hit about 240f or higher on a car that typically runs 190-205f, Too hot. Air in the system can cause erratic readings. Bad pump or failed radiator fans are possible.

These cars won’t rough idle with a hg except on occasional cold starts. Otherwise the coolant can be consumed without a misfire. Often without codes. If hg fails were not so common I might focus elsewhere but they are very common on these engines. New design head gasket, pistons and rings were used by 2015. You and I have earlier models.

 

Pump causes overheating and temp lights. You should see coolant flow into the reservoir when warmed up.

To remove air I would probably drain the coolant and measure. Typically you will get about five quarts which can be reused if it does not have 70k miles on it already. Distilled water at $1 a gallon can be used to completely fill it until you or a hybrid experienced mechanic (recommended) figure it out. Run engine when filled in Maintenance Mode with cap off to release air. Watch coolant temp with scanner. At 190 or higher you can use a flashlight to observe coolant flowing into the reservoir from the bottom hose. That would indicate an open thermostat and functional pump. Don’t do this without monitoring temp since there is a problem. Once the air quits bubbling out fill again, cap and drive with scanner monitoring temps.

Radiator fans should come on with the AC. But they are two speed so the best test is with a bidirectional scanner to command them on. When it’s really hot >205f or so the fans should come on without AC.

No coolant in the oil on these engines! It burns the coolant which then goes out the exhaust. Bad bad end stage hg leaks will blow white smoke when the engine is rev’d up. You have to be back there to see it, but this is new engine time late stage. Normal hg leaks are not observable as white smoke because it is so slow to leak into the cylinder, typically when cold.

A borescope test under pressure is the definitive hg test. See my post from Sunday.

 

Has the miles been mentioned?

 

Good you've read enough to know that. Exhaust Gas Recirculation components (including intake manifold) ever cleaned?

 

Not likely to be anything else but head gasket seepage and if you're going to take it apart to fix that and there's any oil consumption going on you may want to go ahead and figure the extra time to pull the lower girdle and pan off the bottom of the engine undo the rod caps and push the pistons through the top of the cylinder with the head off and out and fit the new tension rings for oil control and I guess new compression rings since you have the mess out I don't know that the compression rings have changed but that dainty little oil control ring from what I understand are certainly changed. If you ever looked at another non Atkinson cycle normal engine you generally haven't seen oil control rings like these these things look like something from cosplay jewelry If I would have seen this in the junkyard apart I would have never bought a Gen 3 just for that. But my time in the salvage industry ended in like 2002 or 3 right it's the first Prius was being released to the market or the second generation rather. I had seen a few of the first generation sedans come in I really like them but they look very cheap and like they would not go the distance. The minute I saw the generation 2 I remember when my friend first got one it was like $30,000 I knew that car was kind of special It was very different from the first generation it carried with it in his genetics the lift back from old TE37 and 57 Corollas and other things that Toyota people would recognize pretty instantly. Very much unlike the generation 3.

 

You need new pistons and rings. The pistons were changed as well.

Also the op needs to have the head sent to a machine shop for an inspection and rebuild.

By the time you do this much it makes better sense to install a professionally rebuilt engine if years of ownership is the plan.