[Cruze2.0TD]

Very common for it to boil if not under pressure. I actually once heard that this was part of the reason a 6L Powerstroke blew head gaskets (I only heard it once and I know it's not the primary reason, but it might've been a contributing factor). Apparently the radiator caps on the 6L Powerstroke didn't properly seal. So there wasn't enough pressure to raise the boiling point and a 6L pretty much just pumped through boiling coolant, which is hard on head gaskets. As I said, may not have been the primary reason the head gaskets failed, but could definitely be a contributing factor.

I'm thinking if it was just for five minutes you're fine. Just don't do it again!