Aleromod comes through again!
 

Needed a coolant reservoir bottle. Come here, do a search, get the brand to buy (acdelco), where to get it (Rock Auto), and plenty of instructions about bleeding the coolant system.
I don't post much, but I'm here, and this site is very helpful!

So this morning no heat from the defroster after engine is at normal temperature. I notice the temp gauge goes to normal, a little above normal, then back to normal, thats when the hot air starts blowing.

Call the shop I use, ask them to come get the car from my work and replace a sticky thermostat. He calls back and tells me the reservoir has cracks and that is most likely the problem. I had seen the cracks, didn't think they were all the way through. He did a pressure test and said they were leaking.
He asks if i want him to order the part, I say no, just bring the car back and I'll take care of it (thinking about you guys). He says no problem, and there is no charge. I tried repeatedly to let me pay him something for his trouble and he wouldn't have it.

Ok, here comes the questions....

Put the new bottle on, put on regular screw type clamps instead of the squeeze type hose clamps. Bled the air. No more problems with the temp gauge or hot air from heater.

May be loosing some coolant somewhere. The level was above the full line after bleeding. After about 75 miles it was right on the full line. After another 75 miles about a quarter inch or so below the full line.

I did notice while revving the motor to force the air to the top of the bleeder screw, the level in the bottle would go down then surge up when I let off of it. Normal?

Could air still in the system cause the level to go down?

Anyone have experience with UVIEW 560000 Combustion Leak Tester?
https://www.amazon.com/UVIEW-560000-.../dp/B000NPDL76
If it should be a LIMG, this would detect it. Correct?
Seems like this would be a quick easy way to eliminate that possibility, if it works as advertised.
Thanks for any replies!

Yes the level will move as the RPMs increase and decrease. That's normal. Also there will sometimes be some residual air that bleeds out as you drive so I wouldn't worry about the little drop in the coolant level. I got air in my system that I can't get out. You can hear it gurgling in the passenger compartment when i shut the car off but I don't have any issues so i just ignore it.

Cool, thanks! Will keep a eye on it.