Low coolant

Last night my low coolant light came on. I was 2 qts low. When I opened the top to fill it with coolant there was a vaccuum. Is this normal? If not what does it mean?

Last night my low coolant light came on. I was 2 qts low. When I opened the top to fill it with coolant there was a vaccuum. Is this normal? If not what does it mean?

Yeah, if your engine is the slightest bit warm, there is a vacuum. At least there is on mine.

That's odd. Every other car I've owned would have positive pressure in that situation.