No Cabin Heat After Coolant Flow Control Valve Replaced, 2008

Hello Prius Experts, I need advice. I received a P1121 code and replaced the three way coolant flow control valve (twice as the first replacement leaked). After the first valve replacement, I filled coolant system and bled air as mostly instructed per this forum and all worked great (except the three-way valve leaked). When I replaced the three-way valve the second time, now there is no cabin heat. Here is what I have done: After replacing the coolant switching valve, the car was on front end ramps and I filled the radiator with Pentofrost A4 through the open cap. I ran car in IG-ON and bled inverter loop at fitting on top. No air in that loop. Then I started the engine and turned up cabin heat to maximum. I ran engine for 30 seconds, and here is where I realized I forgot to reconnect three-way valve wiring harness, but turned off engine right away and corrected (I hope that did not ruin the heater core pump?). I ran heat on high for some time. I am probably forgetting a step(s) I did initially, but to-date I have driven the car many hundreds of miles with the heat on high for a good part of that distance. All else works. No check engine light, AC works great, the climate buttons are all responding, blower blows, it feels like all hoses are hot after running indicating no thermostat problem (?). I hear the coolant heat storage pump run after the engine is off. I feel vibration in the heater core hoses when calling for heat. The volume in the radiator overflow tank dropped a bit over all the driving, but all coolant fluids are holding steady and are full, including at the top of the radiator cap. Just no cabin heat. It has been 90 F outside, but I tried again for cabin heat when the temperature was around 84 F and set temperature to maximum.

Is it possible that there is air still in the system blocking flow to the heater core after all this driving and heater use? One thing I did differently between the two valve changes was during the first time only, I filled the heater core hoses with fluid before connecting them back to the valve thinking this would aid in air removal later. Not sure if this could make a difference?

My understanding is that even if the electric heater core pump is bad, there should still be some heat to the cabin when the engine is running? I thought this pump is only for the convenience of supplying hot coolant to heater core when the engine is off?

And here is something I am confused about. It looks like from the Prius coolant flow diagrams that hot coolant is constantly flowing through the heater core when the engine is running. If this is the case, how am I able to lower the temperature below the current cabin temperature, still run the blower, but not have hot air come out? There must be something that stops the flow of hot coolant into the heater core even when the engine is running when I dial the cabin temperature down below ambient?

Sorry for a long post and I appreciate all advice. Jeff

 

Hi Patrick, thanks for the reply. I figured it out. There was a piece of obviously foreign rubber stuck in the heater core hose return at the three-way valve. I imagine it fell accidentally into the valve at the manufacturer and went into the heater hose. I was lucky it was stuck where I could easily fish it out and now there is heat again. A great relief. Thanks again for taking the time. Jeff