There are two Cadillac Heater Hoses that provide the flow of hot coolant to and from the passenger comportment. These heater hoses are close to the same diameter as a common garden hose but the walls of the hoses used on your Cadillac are much thicker.
The construction of the Cadillac heater hoses are also reinforced with fibers. This gives their walls an added level of strength so they can endure the stress load of transporting hot coolant through them for many years.
After some time and exposure to repeated use of hot coolant flowing through them and the stress of the environment on the outside of them, the heater hoses will begin to be worn. Like all polymer components on your Cadillac, the polymer will dry out and crack in time. With the pressurized coolant in them the walls of the heater hoses will also weaken from the inside out. When this occurs, the diameter of the heater hoses will begin to expand. This is called the ballooning of the hoses. It is most common to occur at the junction of the hose and the metal portals. This can be on the engine block, the heater core or the radiator. If this ballooning of the hose ends is seen by the Cadillac owner, it is only a matter of time before there is a rupture in this section of the coolant system and the loss of coolant will occur.
To test the capacity of the heater hoses to hold in the coolant, they have to be inspected when there is pressure in the system. This is can be accomplished by initializing the heater in the passenger compartment before the engine is turned off. Then there will be pressurized coolant in the hoses so a leak can be seen by the inspector.