[Bill B]

I have a 2019 CTS-V with 4700 miles on it. I had misfiring of the engine going on. Took it into the dealer and as usual everybody knows about their lifter problems. They replaced all 16 lifters and the Plenum above. Got it back now I have 172 miles on it and it makes a noise near the water pump. Took it back to the dealer and the mechanic said it may be a defective water pump. I'm thinking it could be air in the cooling system making a noise since they had the heads off and put in new coolant. It ticks (makes a noise) when you are at a stop sign and when you open the hood it loudly ticks around the water pump area. It still makes the same noise just after you shut the engine off the goes away. I'm thinking it could have something to do with the improper bleeding of the air out of the radiator system and cooler. My lower tank on the overflow is empty and my upper tank is full and you can see bubbles coming through. Is this common? Any help would be appreciated.