Normally a leak in the sytem, either internal or external. More details would be required to expand on the answers to be given
Defective radiator caps or tubes
A leak.
Blown head gasket or cracked head.
pressure test the coolant system you will find a blown intake or head gasket
Can be leaking intake manifold gaskets, which can sometimes be fixed by using Dexcool coolant. Can also be a head gasket.
Could be a blown head gasket, inspect spark plugs for coolant contamination plus loss of coolant and excessive pressure in radiator
excessive muscle loss
your piping for the coolant system or radiator could be leaking and causing a loss of coolant making the temperature rise. Have you had it pressure tested?
A LOCA is a loss of coolant accident. A rupture in the main coolant system resulting in a major leak of that coolant is a loss of coolant accident, or LOCA.
No. Excessive pressure will not cause the water to boil off quickley. It will cause the radiaor hose or other components to burst causing loss of coolant. A bad radiator cap can cause high or low pressure; low pressure will cause the coolant to boil at a lower temperature.
A faulty head gasket will cause power loss, coolant to mix with oil, and is a costly repair. Excessive heat is the primary cause for their failure.
many possible causes, low coolant, worn out coolant, bad thermostat, no circulation (water pump) radiator blockage, pressure loss somewhere