Help with coolant air bleeding

Your electric coolant pump should be running whenever your ICE is on; even when it's not running - to provide cabin heat. The plastic impeller may be loose on the electric motor shaft, causing intermittent flow and function. At your mileage, that's a possibility. Also be careful, consistently overheating your car can blow your head-gasket.

Good Luck...

 

dup

 

Doh!! another Dup

 

Check you water pump seriously sounds like water no move

 

I agree with BiomedO1 that it probably is your water pump. With 212k miles on your car, it is time for a replacement OEM pump. You should also use new coolant if it has not been replaced in the last 50k miles. You can also decide if you want to replace the thermostat. It does not cost very much and it would be a good time to do it.

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Have the EGR (Exhaust Gas Recirculation) components and intake manifold been cleaned?

 

Replaced with what? The OEM front exhaust pipe? Or something else? And who did the replacement?

That coolant circuit that goes down there is part of the bypass path: the small amount of coolant that still can circulate past the thermostat even before the thermostat opens. That's critical, because the temperature of that bypass flow is what makes the thermostat open so the radiator is brought into play when it's needed.

The heater core is also part of the bypass circuit. (That's why you can normally start getting some heat even before the thermostat opens.)

It wouldn't be bad to get some clear pictures or video of exactly how the coolant plumbing was put back together when the cat was replaced.

Also, there are two engine coolant temperature sensors, one right on the cylinder head, and one on the rubber hose at the back of the engine bay, where the coolant comes back up from the exhaust. A scan tool can show both of those temperature readings. They could be interesting to watch as the engine warms up.

Was the car driven at all between the theft of the cat and the repair?

A good rule for random videos on the internet is: if it shows the same procedure that you read in the repair manual, it's worth following. Or if it shows a procedure that is different and it explains why they changed it and why that's an improvement (and the explanation is convincing), it may be worth following. Otherwise, it is worth exactly what you pay for random videos on the internet.

Per the repair manual, you would fill the reservoir all the way to the B line (which is above the full line), put the cap on tightly, start the engine in maintenance mode and run it to thermostat-opening temperature and several minutes more (while carefully shaking and squeezing hoses), then shut everything down. When you look again after everything has cooled down to ambient temperature (takes quite a while), the level should have dropped from B down to the full line, because that coolant swapped places with the remaining air that was in the system.

Doing it the way that's in the manual has always worked for me.

I don't know that there's really an electric motor shaft that the impeller sits on. The motor electronics create a rotating magnetic field, and the impeller just sits on the wet side on a bearing, and contains permanent magnets, so it spins in the spinning field.

But it is plastic, and sometimes it separates (so it spins extra fast without moving much coolant), or sometimes it kind of delaminates and swells up and binds in the space where it spins, so it spins extra slowly without moving much coolant.