Exhaust assembly temperature regulation for shutdown

An exhaust manifold comprising:

• a conduit oriented about an axis, wherein an exhaust gas is configured to flow through the conduit away from an engine;
• a coolant passage oriented about the axis radially outward of the conduit, the coolant passage including an inner shell and an outer shell that define a coolant volume;
• an expansion reservoir in fluid communication with the coolant passage via a first conduit, wherein the first conduit:
• has a first diameter greater than three-quarters of an inch;
• and
• has a positive slope with respect to gravity along an entire length of the first conduit from the coolant passage to the expansion reservoir;
• and
• a coolant reservoir in fluid communication with the expansion reservoir.

An exhaust assembly comprising:

• an exhaust tube oriented about an axis, wherein an exhaust gas is configured to flow through the exhaust tube away from an engine;
• a radiation shield oriented about the axis radially outward of the exhaust tube;
• and
• a coolant passage oriented about the axis radially outward of the radiation shield, the coolant passage including an inner shell and an outer shell that define a volume for containing coolant;
• an expansion tank fluidly coupled with the coolant passage by a first conduit, wherein the first conduit:
• has a first diameter greater than three-quarters of an inch and configured to enable coolant flow in a first direction and vapor venting in a second direction opposite the first direction simultaneously;
• and
• has a positive slope with respect to gravity along an entire length of the first conduit from the coolant passage to the expansion tank;
• and
• a coolant reservoir fluidly coupled with the expansion tank and configured to provide coolant flow into and out of the expansion tank by a second conduit in response to sensor data from a level sensor to maintain a coolant level within the expansion tank, the second conduit having a second diameter less than the first diameter.