Just had my heater core replaced a few weeks ago. 99 S70 AWD. Coolant light went on and off and the coolant level was about an inch or so under the min line. I took it to the dealer who did the heater core and the mechanic opened the resevoir cap and the coolant level came up to the top. Checking with a pressure test this morning, could it have been just an air bubble or air in the lines fom when they did the heter core?

 

It is possible it was an air bubble.

 

I second the air bubble.