Electrically Burned two water pumps

As Chapman noted please purchase this to replace complete assembly:


2017 Toyota Prius Outlet, water. Side, engine, radiator - 1633137100 - Genuine Toyota Part


Make sure you buy the paper gasket for the ‘Outlet Water’ too.

Our Shop had an extra USDM Gen 4 motor so we took that one off for a confirmed fit.

Once switched - Throw it out or use it as a reminder that you wasted 2 water pumps LOL as a learning experience.

 

The water pump pulls water in through the water-inlet-with-thermostat directly behind it, from the bypass circuit (all the time) and the radiator (when the stat is open). The pump discharge into the front of the block, high point of static pressure in the system, is right where that timing cover nipple is located. So the most interesting part of your theory is what would be pushing the coolant in at that point against the pressure gradient. (Unless I've misread what you meant by "opposite as per your theory".) If you have seen it documented, or if you have inserted a flow meter in that line and confirmed the direction, that would be good info. I'm not saying I can't be wrong.

I wasn't sure from the pictures how many connections are in that tee attached to the water outlet, but a better picture makes it look like only the two coolant connections, plus yet another electrical one:



So, just the one connection from the water outlet to the EGR cooler, same as we have in North America, plus the one extra connection back to the nipple at the water pump discharge.

In our North American diagrams, we send coolant from the water outlet into the EGR cooler (fat nipple on the bottom), and the cooler has both a skinny and a fat nipple on top. From the skinny one, we cool the EGR valve itself, de-ice the throttle body, and return to the water pump through the thermostat bypass.

From the fat one, in a car without the exhaust heat recovery system, we head straight for the cabin heater core, and from there it's the home stretch into pipe 1628A and back to the water pump through the thermostat bypass.

In a car with the EHRS, after the heater core there's a detour down to the exchanger on the exhaust pipe and back up again, to pipe 1628A and back to the water pump.



While both the EGR cooler and the EHRS do "heat up the coolant that flows inside the cooler fins", the EHRS is the one where that's done for the purpose of heating up the coolant. What it's being used for in the EGR cooler is to cool the EGR. In neither case, anyway, would that settle the question of flow direction in that added line.

Anyway, those are the North American routings, because I don't have an easy way to study the Euro/Japan ones. There is definitely something interesting they've designed there and it would be interesting to know more about. If it were necessary to get across the Gorge of Eternal Peril, I too could probably give a glib answer when I don't really know. But as long as the Bridgekeeper isn't rushing me, I'm ok with waiting for somebody to have time to look it up.

 

Great!

You will need to be creative on that part.

We took the original hose that was attached to the outlet and plugged it on the hose side by shortening the length and sealed the deal with a hose clamp.

 

Have you paid much attention to what the suction and discharge directions always are for a centrifugal pump



or compared that to what you see when you look at your water pump?



To go over it again, the pump sucks coolant in through the elbow fitting containing the thermostat (which in the parts catalog is called WATER INLET SUB-ASSY W/THERMOSTAT). It pushes the coolant into the front of the engine block.

This is not much different than you're going to find in any car you look at.

Up until the thermostat opens, the water being sucked in is just what comes through the bypass nipple on that elbow, which is coming back from the EGR/cabin heater/EHRS/throttle body.

After the thermostat opens, it also takes coolant in from the fat hose at the bottom of the radiator, where it is coolest.

The water going into the far side of the radiator, for cooling, is what's coming out of the (wait for it) OUTLET, WATER.

There are a lot of posts where it's fitting to add a humble note that I might be wrong, but this one right here isn't one.

 

A person being tidy about it might use a short length of the hose and a barbed plug, I guess, secured with a hose clamp or clamptite. More than one way to skin a cat.

 

The manual says this, and this test confirmed it:



However (COMMA!), keep in mind that note *2 appears in a special place in the manual: it's in the table showing what happens when a code for a water pump problem has been logged.

If the ECM has not detected a water pump problem, it does not stop the engine at 105 ℃ (this test confirmed that). I do not know what temperature it will shut down at, if it ever does, when there isn't a water pump problem on record. I chickened out at 107 ℃ and there was no sign of an overheat light, much less shutdown, by then.

Later learned (this test) the red overheat light comes on at 248 ℉ (120 ℃), but I did that test just by electrically spoofing the sensor until the light came on. I've never taken my engine anywhere close to 120 ℃ for real. Also, I have never done a similar spoof test with the other temp sensor (the one in the cylinder head and connected to the ECM).

I personally don't know very much about what conditions are likely to warp the head; metallurgy isn't my thing. I compensate for that ignorance by striving to avoid anything close to overheating ever.

 

Not for me—I go to the Toyota dealer, they grab it off their shelf.

 

Spoofing works (and can be done with a simple resistor, no need to boil a spare sensor). Running the actual engine does too; I did that in this test and deliberately ran the engine hotter than 221 ℉ when no pump code was present, and there was no shutdown. And that's consistent with what the repair manual says, where the 221 ℉ engine shutdown is only when a pump code is present.

I can't say what happened exactly in the event you're reporting here because I wasn't there, but generally, the repair manual is right 99.99% of the time, and when the repair manual agrees with a real-world experiment, that pretty much takes care of the other 0.01.

My first, second, and probably third guess would be that something might have happened between that shutdown and when you pulled the codes, and if you had pulled them right when that shutdown happened, the power management control ECU would have had P0A0F-206, and the ECM would have had one of the pump codes. Hard to go back in time and replicate it though.

 

Changing the water outlet seems to be a good call, given the paucity of real information about just what the Euro/Japan design is meant to do. (I'm kind of surprised @Elektroingenieur hasn't made an appearance with details yet, but I guess nobody's around PriusChat all the time, or maybe we're not paying enough.)

I ordinarily try to change not so many things at once when I'm trying to figure something out, because past a point it just means even if you think for a while you did something that fixed it, you'll never know what.

I know it can be hard to stick to that when in a hurry and frustrated though.