2011 Prius Overheating issue coolant reservoir getting hot and red temp light turning on

Well these radiators don't generally plug up too easily unless prior owners had similar problems and tried to use any of the snake oils in the radiator the little pellets the glue whatever the poison they just picked one and off they went rather than really repairing they went for the pour in the radiator type fix. Or something along those lines these cars just having plugged up hoses and plugged up waterways is not a thing unless it's induced by humans doing silly things but they read in an advertisement or saw on TV or on a YouTube video. So what's you're telling me is is that if you slow down to 70 miles an hour you'll never see the over temp light think about the question now Is that what's really happening. What temperature are you traveling in I didn't look at your profile to see what state it says you're in is this in 75 80° weather 100° weather out It all makes a difference are you absolutely certain that all the air has been burped out of the system? It's hard to know where is your coolant level sitting in the jug right now what is it on line one. Two. b? That's a good place to start I don't know if you're paying somebody to do all this work? Or you have a little bit of capability in this department burping hoses and just looking over all of the connections is a place to start the lower the hoses are in the system they should be full of coolant when you squeeze them you should hear the liquid moving in the hose You squeeze it like you're milking a cow Right smartly at that and quickly and you hear the liquid moving as you're squeezing go over to the other fat hoes it runs between the transmission the engine and over to the radiator squeeze it you hear the liquid moving doing this when the car's been driven about 15 minutes and it started to warm up gives you an idea of what's going on after a good run everything should be decently warmed up You shouldn't be really be able to be holding on to the main hoses for too too long without you backing off because of the heat things like that. With the engine being changed and all that going on without knowing exactly how the work was done and what all went on hard to say when the person swapped out the engine and put it all back together were there any problems with codes for the water pump and all that? Maybe that's why the water pump got replaced? Does this person doing the work have the Toyota software to turn the pump on and off manually while the software is plugged up to the car? All of these things make a difference and getting the car running correctly when this heat light is flashing If you got out to the side of the road whipped up the hood and had something like a temp sensor gun one of those infrared heat guns and shot at the hoses are you overheating like $199 to 205° this tool would tell you that pretty quickly It's hard to manually do it but that would be hot enough so that if you touch the hose you'd move your hand away immediately unless you do this sort of thing regularly.

 

Saying your mechanic "replaced everything" is not specific enough... I'm sure you could name all kinds of things that haven't been replaced. Like the radiator... I bet you haven't replace that yet?

Has the inverter cooling system been flushed? Has all the air been bled out of the system? Being able to see the inverter temps and inverter function as it heats up on Toyota Techstream on an old windows laptop is going to be where you're likely to identify what's wrong.

Also is your MPG normal?

 

Suspect your only problem is when you say: "I have issue when I drive high speeds 70-80 mph up hill."

And now that I realize you're doing this during the craziest Northern California winter ever? Or more to the point, Prius are designed for good gas mileage in the slow lane... Sounds to me like you're pushing a weak low horsepower 18 year old vehicle to to the brink of failure because you didn't match your driving habits with your car's abilities...

I bought my '07 Prius in Sacto a decade ago and know exactly the hills around you that you're referring to and that fast up those hills in a Gen2 means you're a good candidate for engine failure and don't need to worry about inverter temps, it's probably just the other half of radiator that's used for the engine that's running hot because you're up above 4000 rpm way too often.

If you don't want to lose your Prius to a break down get an ODB2 reader and use car scanner app to monitor engine RPM on hill climbs and base your speed on 3500 RPM, which is peak power... Anything above that, especially 70-80mph up steep hills is going to lead to premature engine failure!!!

 

Like stated above try 65 just to see if that solves all the hullabaloo because changing your radiator and inverter pump I don't think it's going to net you much more cooling capacity unless it's completely non-functioning right now which I kind of doubt the car would be telling you.

 

Just keep paying to have parts replaced. Sooner or later the problem will get fixed.
Don't worry about actually checking to see what the actual problem is....

 

Peak power for a Gen 3 engine, 73 kW (or 98 HP) happens at 5200 RPM. (If this were a Gen 4, it would be slightly down to 71 kW, also at 5200 RPM. Gen 2 was 57 kW at 5000 RPM, and Gen 1 was 52 kW at 4500 RPM. There weren't any generations where peak power came at 3500.)

It doesn't take any special driver attention to avoid exceeding the peak power engine RPM: whichever generation Prius you're driving, the car knows what that RPM is, and doesn't exceed it, whatever you do.

There's nothing wrong with having some lower percentage of peak power be your personal driving target, and that may well help things last longer. Definitely the car will use oil faster at higher RPM; be sure to check the dipstick more often if you do a lot of sustained high-power driving.

If you do get an OBD2 reader, there are lots of things you can watch to guide your driving. Engine coolant temperature is always one of the four things I show on my ScanGauge. If you see that getting elevated, you can take it a little easier up that hill. Battery current is another. If there's a sustained positive current (power out of the battery) being needed to assist you up the hill at that speed, you'll be in for a surprise at the moment the declining charge reaches 40% and suddenly you'll be going much slower. If you keep the climbing speed down to where the battery doesn't have to be steadily contributing, or maybe gets charged a little, that's a more sustainable speed.

Or you can watch things like the efficiency / MPG readouts right on the combination meter, without needing an OBD2 reader. You get better efficiency holding things to mid-loads than you get at peak power.

 

Two main things to check if u have replaced the thermostat and water pump.

1. Check the radiator. Get it flushed.

2. The bleeding. Check if u have the coolant bleed valve. Open it and press all hoses to burp the system. If there is no bleeder valve, remove the ECT sensor and press all hoses around to burp the system. Might take u about 30 mins.

Posted via the PriusChat mobile app.

 

The Gen 3 has a degas-bottle cooling system that pretty much burps itself if you follow the filling instructions in the repair manual. That includes filling the bottle initially to the B line (which is above the FULL line), installing the cap, starting and running the engine up to operating temperature and several minutes more while squeezing and shaking hoses, and then shutting down and allowing it all to cool. After cooling, the level should have gone down from B to FULL on its own, because the coolant traded places with the air in the system.

Some early Gen 3s came with an extra valve you could open in the hose at the back of the engine where the EHRS return temperature sensor goes, and the repair manuals for those did have you open that valve while you were pouring coolant in to the B mark, and then close it.

When they later removed that valve from the system, they also just removed that step from the manual. They did not add any other step, taking the temperature sensor out or anything, to take its place.

 

Ok... But I've read multiple times here that 3500 rpm is optimal engine efficiency regardless of when the electric motor peaks in power... Even went to double check I had it right once I started monitoring rpm. I also noticed a significant improvement in MPG when climbing mountains around the Sacramento Valley and Oregon when trying to limit my hill climbing speeds to 3500 rpm, which in many cases was faster than I was used to going because I'm a typical Prius driver.

Furthermore I've used a couple different apps that monitor RPM and the design of them consistently have given me a green indicator light at 3500 rpm with other lesser colors at higher and lower RPM.

Based on this would it be fair to say that peak ICE torque/MPG is 3500rpm?

 

That could be a solution if you think the temp sensor is lying about what the temperature is, but I'm not seeing that in this story. You mention the reservoir being "hot almost to boiling temperature", so unless the sensor reading is very different, it would seem to me the sensor is ok.

In any case, there is not very much to go wrong with a thermistor sensor. Even if I seemed to be getting a wrong temperature reading, I would look for a wiring problem to the sensor, before I would suspect the sensor itself.

If the coolant is getting too hot and the sensor is telling the truth about that, the problem is somewhere else.

 

In #7 you wrote "engine RPM ... 3500 RPM, which is peak power". Peak power for the engine comes at 5200, and that's straight from the engine specs, you didn't seem to be talking about "when the electric motor peaks in power" and I wasn't either. 73 kW (same as 98 HP) at 5200 RPM is the answer to the gasoline engine peak power question.

Now by changing the question from peak engine power to optimal engine efficiency, yes, you can get a different answer to the different question.



As you can see, the old Gen 2 engine could run as efficiently as 230 grams of fuel per kWh energy produced, and it could do that in the small gray area between about 18 and 38 kilowatts. The newer 1.8 L engine for Gen 3 has a much larger area where it can reach 230 g/kWh, reaching from all the way down to 10 kW to up well above 40 kW, and within that area there is even a small region where it can be as efficient as 220 g/kWh, between about 12 and 32 kW, in the RPM range that looks to be from 1200 up to just about 3000. So if you are looking for optimal engine efficiency, you'll want to keep your RPMs within that range.

And posing a third different question can yield a third different answer.

You'll notice the highest-efficiency, 220 g/kWh range tops out at just over 30 kW ... less than half the capability of this 73 kW engine. So that's great for when you're tooling down an easy road and 12 to 32 kW will do the job. Any other time, when you need any more of the power this 73 kW engine can give you, you're going to have to venture outside of the highest-efficiency zone.

You'll also notice something interesting in the way the ECM controls the engine. Up to 3650 RPM, it is not asking for the maximum torque the engine can produce. It knows the optimal-efficiency region lies on a lower torque line, and it keeps the engine operating on that lower line, up to 3650 RPM. Above that, the ECM asks for increasing torque along a straight line between 3650 and 4000 RPM, and then follows the engine's actual capability from there to 5200.

You can see how that straight increasing-torque line doesn't leave the 230 g/kWh region until about 3900 RPM. So if you were stating the question as "peak torque / g/kWh" then the answer would probably be up in that neighborhood, where the g/kWh is still pretty low and the torque's a lot higher.

Peak torque regardless of efficiency is of course the peak you plainly see at 4000 RPM, just as the engine specs say.

But stating the question as "peak torque / MPG" makes it also depend on road speed, therefore conditions outside of the car, therefore harder to give a general answer in a forum post. (Also, it might make a better question as "peak torque / GPM", because putting MPG in the denominator makes the result "peak" at the worst you can do. )

In practical terms, if you're mostly interested in keeping the engine in the region where it's most efficient most of the time (and who isn't?), you don't need a separate scan tool; the car already knows how those efficiency curves work and can show how you're doing on the MID, so you can just watch that.

But again, that most-efficient region tops out under half of what the engine can give you, and sometimes you just need more power than that. At the higher power levels, you won't be as efficient (but still pretty darned efficient), and the car still also knows where the peak power limit is, and it won't exceed that, without you having to worry about it.