Cylinder 2 misfire then coolant level drops

[tangelogee]

Hi all,

So I have this odd issue with my 2016 LT, around 89,000 miles. Around January I had the upper radiator hose burst on me. Got that replaced, but after a few weeks I've had an issue with 2 things:
1. The coolant level slowly goes down over about 2-2.5 weeks, and I have to check the level almost every day to keep it from overheating.
2. Occasionally I'll get a P0302 code with a flashing CEL. If I turn it off and start it again, it seems to run fine, and anytime other than at idle it seems to run just fine. I may be imagining things, but it seems like the coolant level drops more after this happens.

I recently had the spark plugs replaced, the fuel injectors cleaned, and the water pump replaced. The water outlet has been replaced about a year ago, but only with the plastic replacement. The coolant system has been pressure tested multiple times, and it seems to stay under pressure, and I don't see any obvious leaks, so I'm not sure where the coolant is disappearing to.

Any ideas on what I should look at next? Aside form this issue, I still love to drive my Sonic, but I can't afford to keep throwing parts at it for what its value is.

 

[Frankh]

Well the pressure test should have discovered the leak.. Did you look down inside cyl #2 with a borescope after it was under pressure test for several hours with a cold engine?

 

[tangelogee]

Well the pressure test should have discovered the leak.. Did you look down inside cyl #2 with a borescope after it was under pressure test for several hours with a cold engine?

I don't have a borescope, but I guess I could get one and give that a try. Thanks!

 

[Frankh]

You can buy a borescope camera that hooks up to your phone for about $15 on Amazon.

This will fit down the sparkplug hole.