Need help! Gas engine overheating. Cannot resolve.

mmmm very strange. Are you sure you've all the air out of the system?
Did you check to make sure the fans are sucking IN the air?

 

Fans are drawing air into engine bay. Checked codes showing p148F

 

Have you checked your oil? Is it low? I know guessing isn't the best way to trouble shoot,
but running out of things to check...
Again, are you SURE you got all the air out of the system? I know you tested the thermostat,
but are you sure it is opening?
Have you used techstream, or anything else, to determine if the water pump is moving the
coolant fast enough? It may be flowing, but not fast enough.
It just seems you are missing something, something simple?

 

Oil is fine not burning also coolant doesn’t disappear. I don’t have techstream.

 

I’ve tried getting air out of the system but it is so hard. My car has the bleeder valve but air looks like it doesn’t want to bleed. That’s what I think.

 

How come I get the feeling it's a head gasket.

One bottle of K-Seal, on sale at AutoZone...

moto g(7) power ?

 

Higher load (high speed, load, or uphill) overheating can often be a head gasket. Just ask the thousands of Cadillac owners with the NorthStar 4.6 engine. One thing that I have seen on some other cars that overheat at higher speeds is the water pump suction hose collapsing and restricting flow. I've seen it mostly on cas with mechanically driven water pumps.

 

Yeah, having read such weird occurrences/phenomenons over there, this kind of reminded me of them! Thanks. I'm not the most knowledgeable of the bunch...

moto g(7) power ?

 

Thanks for the amazingly clearly presented and informative description. Glad to read that you eventually got it fixed.

I did not see this thread until just now (and did not even have a Prius back then), but a couple of comments that may have helped you and may help others:

I notice on the AWESOME temp plots how the temp behaves during the "spike" periods. It tends to increase steadily, and has multiple fairly rapid drops in there. My first thought looking at that was that an air/vapor pocket was forming, reducing heat transfer locally at the sensor, allowing temp to rise. Then the pocket would collapse or move on; as soon as that would happen, the quenching coolant would fairly rapidly suck the heat out, dropping the temp just as you see.

The other thing here, in general reflected by the very sudden change in temp ... there's no way the whole engine will change temp so suddenly, either up or down. So this points to that info being only locally true - i.e., the temp at the sensor is varying like that, but the rest of the cooling system will be doing something else. It would make sense that a sensor(s) would be placed at an especially high / critical location - e.g., the hottest point, right at they cylinder head exit. So the brief overheating seen here does not mean you definitely had an overall engine overheating issue that may have warped the head, for example.

So my advice would have been to focus as much as you can on bleeding. I am not really familiar at all yet with these Prius cooling systems, so all this info is general. But applying a vacuum to the cooling system while bleeding will cause any air pockets to expand, making it easier for the coolant to get in there and fill those spaces. Some cooling systems (e.g., modern Porsche) REQUIRE use of vacuum bleeding systems as the proper way to do it (vs. as a troubleshooting step), and they are pretty cool - e.g., some pump coolant through the system with a venturi-generated vacuum to suck the bubbles out.

The other (unrelated in your case) general comments on the water pump overspeed ... It seems that might be caused by a few things that should be considered during diagnosis and repair:

• lack of coolant may allow the pump to over-spin. Since it's the easiest thing to go wrong, inspect, and fix, this should be the first candidate.
• as reported to be common on these cars, the impeller loosens from the shaft, again allowing the shaft to overspin while the impeller does not keep pace. Since it has been reported as a problem on these cars, it makes sense to consider this one next, but ...
• This one I have not seen mentioned yet ... A blockage in the system somewhere will slow or almost stop coolant flow. A non-intuitive aspect of how these centrifugal impeller pumps work is that when flow is blocked, the load on the pump drops significantly, which would cause it to overspin, accompanied with an increase in coolant temp due to the reduced flow.

 

Just wondering - my understanding is that the water pump is pcm (pulse code modulation) controlled. Because of this, it has an advantage over "manual" pumps such that it can actually monitor the rpm of the pump through feedback. Doesn't it throw a code (p0261 or something like that) if the pump speed isn't as expected?

 

@Mendel Leisk

I'm about to attempt this with my vehicle (due to overheating issues). One thing I am not quite clear on: am I suppose to be removing the coolant hose atop the egr WHILE the engine is running in maintenance mode? At what point should I expect coolant to flow upwards through the egr cooler, to place the hose back? As soon as the car is turned on, or once the thermostat opens? If it's the latter, wouldn't the coolant be around 195 degrees Fahrenheit - enough to scald skin? Because of that I'm wondering if perhaps the method you are talking about works at lower temperatures, without assistance of the thermostat. I will admit a certain level of ignorance on the workings of the coolant system.

 

The hose should only be pulled off while your refilling the coolant, engine off. Basically to allow the air an escape route. Hold your hand over the open ends and you should feel air blowing as you pour. If you don't, then maybe it's not effective, just push the hose back on.

For some reason the vent was discontinued in 2012, not sure why. Maybe ineffective??

I'll be doing a first Prius coolant change myself this fall, am curious how effective this vent is.

 

Has anyone tried putting the 2010/11 air vent connector in the later models? Seems like it would make the entire process much easier.

For the past few days I have had an issue of overheating up to around 240 (after about ten miles of driving). I can still drive short distances however. I've tried bleeding air by lifting reservoir up above the engine. While that did help a little, it was still heating up to 230. Yesterday I back flushed the heater core (and filled it with coolant before hooking things back up). I would have thought that would have eliminated any air bubbles in the heater core. However, if anything it was back to running at 240 after a few miles driving.

Today I removed the top egr hose, poured coolant directly into the top egr port, then poured it directly in the hose, reattached the hose, then removed the sensor (near what should have been the air bleed valve), poured a little coolant in that, reattached the sensor and preformed another bleed in maintenance mode (this time without lifting the reservoir up). Around 205 I noticed the level dropped a little, and started regulating around 188-193, so I figured I was good. Took it out for a test drive and could not drive more than a mile without the temperature spiking to 240.... after popping the hood I hear a loud electrical sound (video below). Sorry for the shaky cam - I could not see anything on the screen so I was trying to adjust the brightness.

The current water pump is from the 4th gen engine (I did a 4th to 3rd swap), and has 47k miles on it. I do not recall hearing this sound prior to today... though I could be more aware of it than usual.

My next attempt will be to flush the entire system, and then do as you say and unplug that egr hose to let air escape, and fill the entire thing again. Perhaps more air entered the system by trying to pour coolant directly into the egr and hose?

 

Not sure if I've posted before, but attached is Repair Manual excerpt, for engine coolant change, and yeah it definitely says to open the bleed valve (on 2010,2011 model years only if I'm not mistaken).

It definitely was the drill, at least at time of publication:




The above is in line with my Honda experience. I recall the last time I did this, on a Civic. I happened to hold my hand at the open bleed valve while pouring in the coolant, and there was a strong gust of air coming out.

Now why Toyota eliminated the valve is a puzzle. I've yet to go through the process so can't really say. Maybe it was not effective, ie: while you pour in fresh fluid there is no way for air to escape through the vent? And so they eliminated it?

For anyone with a 2012 onward, without the vent, you can dispel the mystery: try pulling off a hose there, just before starting the refill. See if you can feel air coming out as you add the coolant.

Toyota makes a big deal of saying you should attach a tube to the spigot (on model years with the vent), but spillage is trivial: when you see coolant start to come out, you stop pouring, you close things up, and carry on pouring.

 

The water pump is ELECTRICAL. So are the radiator fans.
I think you are chasing the wrong "ghost" here.

 

I just checked codes and have a P148F - Engine Coolant Pump Over Revolution.

As I said before, the coolant pump itself only has 47k miles on it (it's the stock coolant pump for that engine). However, I have read that there is a failure mode where the pump impeller separates from the motor shaft. The question is why would the pump fail to begin with??? It just seems odd.

 

@Jacob Bonner you don't have a 4th gen engine transplant do you? Or do you? I'm losing track.

Ok you did say, just up the page. And sorry for my flakey memory, we've talked about it before.

 

I have a 4th gen engine in my 3rd gen car.

I'm genuinely concerned over this because I am reading reports of people repeatedly burning out their $300 4th gen water pumps over what is effectively an electrical problem... maybe the ECU is fried, maybe the wiring has a short, maybe maybe... I'm around $3000 now on fixing my car and still nowhere close to being done with it apparently. I was fine until yesterday. I could at least drive it to work (a couple miles) without it exceeding 210 degrees. Now that's done with. I'm back to not having a driveable car (for more than a mile anyway). I've been fighting with this since February of 2019... I've honestly about had it with the Toyota Prius.

 

Somewhere here, very recently (apologies if it's right up the page), someone was saying there are significant differences between 3rd and 4th Gen water pumps, specifically something in the gears? It's electric though?

@sam spade 2 's covered that question.

 

Have you actually tested the water pump? Using TechStream?
You say you have a Gen 4 block. Are the 3rd and 4th Gen water pumps different?
Will a 3rd Gen work on the 4th Gen block?