There's an air bubble in your coolant. Burp the coolant.

Every DSM I've owned had a heater that worked like Satan himself designed it.

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!