Electrically Burned two water pumps

I'm not sure how good I feel about that. If you look at the original Gen 3 routing:



You can see that the Gen 3 EGR cooler has that long descending leg in front, which leads directly back to the bypass inlet on the thermostat housing. The throttle body gets warmed from that dedicated nipple on the Gen 3 cylinder head, and flows into the side of that EGR cooler pipe on the way back to the thermostat bypass inlet.

If you compare the Gen 4 routing (little harder to read, have to follow more dashed lines and ①s and ②s and ③s):



The Gen 4 EGR cooler no longer includes that collector pipe that goes back to the bypass inlet; that's just the separate pipe 1628A in Gen 4. The Gen 4 cylinder head no longer has that extra nipple to send water to the throttle body; instead, there's an extra skinny nipple on the Gen 4 EGR cooler, and what comes from there goes through the EGR valve first, and then to the throttle body, and from there flows into the side of the 1628A pipe on the way back to the thermostat bypass inlet.

If you've got a Gen 4 head and a Gen 3 cooler, the thing you're missing is anyplace for that throttle body coolant flow to come from: you haven't got the skinny nipple on the head, and you haven't got the skinny nipple on the cooler.

Where the throttle body coolant flows to isn't a problem; sounds like you've got that still flowing into the side of that collector pipe going back to the thermostat bypass, which is right. But teeing the supply end into the burp line where you did seems slightly weird.

Maybe it works out in the end anyway. I assume you still have the 16281 burp line, and maybe you got rid of the 16577C pipe, and you connected the burp line instead to the skinny burp nipple on the 16331 Gen 4 water outlet. Probably about as close as you're going to get to a dedicated extra hot-water-out nipple on the cylinder head anyway, except for the way it's positioned high up on the outlet for getting bubbles out.



So maybe it more-or-less works out. I don't know if it's worth trying to arrange things so your throttle body line comes off downward while the burp line follows an upward path, to try to encourage most bubbles to return to the reservoir and not get slurped into your throttle body circuit.

Curious how RightOnTime arranges it.

 

Glad you worked things out!

Just remember - since you messed with the jiggle pin and drilled another hole in the thermostat you might have issues with a longer warm up time and or operating temp.

Don’t know if that’s a good thing or a bad thing. Just keep us posted

 

Remembered this thread when I saw that rjparker found a reference that says a little about that system anyway. It's not from Toyota, but it's from a non-US auto research outfit, so it has some info on that non-US-market contraption.



So, "flow shutting valve". Kind of like a thermostat, but electrically controlled, and in addition to the regular thermostat that's still in the regular place.

Part of what they say about it has to be wrong ("previous Prius models coolant did not flow to the heater during warming" is nonsense, and their explanation doesn't square with their diagram), but it is a good diagram with the general directions of coolant flow.

So coolant can always flow directly from the water pump discharge back to the EGR, cabin heater, and EHRS, and when the flow-shutting valve opens, coolant exiting the cylinder head can join it.

The coolant coming straight from the pump discharge will be cooler than the coolant coming out of the head. So with the FSV closed, lower temperature coolant is going to the EGR and EHRS, meaning it can pick up more heat from the EGR and EHRS and warm up faster. On the other hand, if you want more cabin heat, the FSV can open and the hotter coolant from the head joins in. Decreases the efficiency of picking heat up from the EHRS, but increases heat delivery to the cabin. (And anyway, the EHRS is downstream of the cabin heater, so by taking out heat for the cabin first, the coolant ends up at a lower temperature, better for harvesting heat from the EHRS.)

Interesting trade-offs; it would be fun to see what their actual rules are in the ECM for when it opens and closes that valve.

 

So how did that work out for you? Burn up anymore pumps? Anymore overheating issues??

 

So how did that work out for you? Burn up anymore pumps? Anymore overheating issues??