Coolant issues
 

When I blew my head gasket, we replaced the water pump just to be safe. According to a lot of reports on iATN, these pumps, when they fail, will fail intermittently, and so they may cause overheating with or without a coolant temp light. You might be seeing your water pump start failing...

If the coolant light is flashing, on most cars that typically would mean that the level is low or there are large air pockets that are making the sensor intermittently trip. As well as cause overheating.

So you should first ensure the system is purged of air THEN ensure the level is correct. And try again.

Thanks for saying the water pump has a high pitched whine. I've noticed a new sound (high pitched, generally with light acceleration, never when the ICE isn't running) with our new engine and wasn't sure if it was just from being use to the original engine sounds or not. But this is a good clue to investigate further. Thankfully i have a spare water pump at the ready!

One of the things that changed was when I use to get in the car and power it on I could hear the coolant/water pressurize in the system, on Friday I did not hear that at all. We purged the system, and same result. Pretty sure it’s water pump at this point.

Could be. But how would you explain the coolant light? Assuming it means low coolant, which from my quick google search, it does. An underdriven pump could certainly cause overheating, but it wouldn't explain your low coolant light.

Unless you mean an overheating light?

I would need to know the exact light that you received

The “low coolant” light also monitors the temp of the coolant. If it’s just indicating “low coolant” that would make sense as it’s not pushing enough coolant past both sensors. I ran real time data from both sensors and the temp range per the computer 0-130c. The temp was all over the place, and the pump was whiny. It’s unable to keep up, or it’s failing which caused the initial overheating issue. Also the pump is unable to push coolant/water to the heater core now. I don’t hear the system pressurize like it once did. We’ve replaced everything else but the pump. 99.9% certain this is the issue.

Yeah no believe me I'm all for replacing the water pump. I just know from experience that not bleeding the system can cause a lot of problems. I'm in the replace it camp and I would advocate replacing the water pump if you're in there even if it WASN'T failing.

Replace it by all means.

oh absolutely agree! It’s being changed that loud whiny sound has to go.

Update
 

I believe I’ve been having this same issue with my 2012 ct200h. We’re you able to replace the water pump and did it resolve the issue?