Replaced coolant flow control valve, now overheat light coming on... need to bleed air?

I was getting a check engine light with a P1112 code, so I had a mechanic replace the coolant flow control valve. There's a TSB on that and it seems to be the thing to do. But after the replacement, I'm getting overheat warning light whenever the engine needs to work hard. Also, the cabin heater only works when the gasoline engine is not running... when the engine is off, I get heat (though it's not as hot as I'd think when I have it on max heat), but when the gas engine kicks in, the cabin heat disappears.

I've checked coolant levels in both reservoirs and the radiator and everything looks OK. From searching online, it seems likely that this is caused by air not being properly bled from the coolant system after replacing that control valve -- does this seem right to you all? If so, what do I tell the mechanic to do, since they can't seem to figure it out for themselves? Or should I give up and find a mechanic who knows what they're doing?

 

When I first brought it back to the mechanic and asked about bleeding, he did something like that but on a different port. The port he used was not directly on the radiator and wasn't a hex socket. It was also on the driver's side, but up higher and in between the radiator and the hybrid system. It was a bolt with a hose barb on top of the bolt, as part of the bolt. (See photo I just took below; port is in center of photo.) He attached a hose to this, loosened the bolt, and ran the hose back to the reservoir. Coolant flowed though the hose, and a little coolant leaked around the bolt also. Was he using the wrong thing for bleeding?

 

Yeah, so I just opened up the bleeder on the radiator that the PDF you linked to pointed out , hit the power button twice, and all the coolant from the radiator reservoir disappeared... presumably into the radiator or some other part of the system. So they never bled that part of the sytem, only the inverter part. The problem is I don't have any coolant on hand to fix this, but I can take care of that tomorrow.

So I should never go back to these guys again, eh?

 

I got about 2/3 of a gallon of coolant into the radiator, so that explains the overheating. The mechanic is insisting that the two cooling systems (ICE and inverter) are completely separate and that they didn't drain the ICE radiator. But the part they replaced is the coolant flow control valve, which looks to me like it's part of the ICE system, not the inverter system. I think they just didn't know what they were draining, and they tried to fill the wrong coolant reservoir. Now they're embarrassed and won't admit their mistake. Am I full of it, or are they?