05 GXP Head Gasket?

[Sullivan]

Good even all, hope you all are doing well tonight. My bonneville never ceases to amaze me as far as problems coming up at inconvenient times. So about 2-3 weeks ago I had to replace my radiator and that was alright and everything came apart and put back together just fine. Unfortunately I am still on a bad streak and now I have a feeling that the head gasket has gone. I could be wrong so please correct me if I am. So what is happening is whenever I leave the car for maybe and hour and a half or let it sit overnight, on start up the engine is misfiring and chugging for about a minute or so and then a lot a white smoke comes out the exhaust pipes. The engine does smooth out and I'm assuming that it is just working all of the coolant out of the cylinders, but the white smoke says around until the car is heated up for the most part. It is cold this time of year so I know pretty much every car is putting out steam, but mine are just very large so I know something is wrong. I am experiencing a little overheating, but I think it is just a air pocket in the cooling system from when I replaced the radiator because it happens maybe every couple of days the temp gauge will rise at the most just a quarter of the way past the middle 200 mark and the next mark and then come back down after a couple seconds. So the reason I bring all this up and really just making the post is that I need this car to last me 3-4 more months or really just through this winter. She has a little under 173k on the odometer and the car really is not worth much at this point. So I am really just looking for some recommendations just to "put a bandaid on the axe wound". My biggest fear is that the motor will not start one of these mornings because of the cold weather and too much coolant in the cylinders. I have seen some people talk about stop leak, but I would be nervous about putting that in the coolant system because it could get into my heater core. Any help or advice is appreciated. Thanks.

[CMNTMXR57]

Certainly sounds like it could be a head gasket issue. But the issue isn't a simple GM cooling system tablets or Bars Stop leak fix away (Contrary to your fear most of today's stuff you can leave in and won't do any damage to the heater core). Also when you say white smoke coming out on cold start. Is it the normal level of condensation/moisture in the exhaust stream that then meets cold air upon exit from the tailpipe? Or is this clear, thick white smoke above and beyond the normal level of cold start condensation? Also sometimes these engines do have a little misfire when cold. Is it triggering a blinking CEL?

The issue is the studs that hold the heads to the block. They're a fine thread bolt and basically corrode and "tear" out under pressure.

Search "Northstar stud issues" (or something along those lines) in google and you'll get all you need to know. The "Correct" fix is to take the heads off and re-stud the block with something like Northstar Performances' SureGrip stud kit.

As always, I suggest starting with simple checks before going for the worst.

[Sullivan]

Yes the smoke is very thick and white upon start up so without a doubt it is above and beyond the normal amount of condensation. Also the check engine light does flash for at the most of 20 seconds and then goes back to being solid.

[Kevin Amstutz1]

Burnt coolant will leave a very sweet smell from the rear exhaust.
What are your CEL codes?