* Combustion gases entering the cooling system: A head gasket's primary function is to seal the combustion chambers from the cooling system. A blown head gasket allows combustion gases (which are under high pressure) to leak into the coolant. This pressurizes the cooling system far beyond normal operating pressure. Even after the engine cools, the pressure from the trapped gases can remain.
* Hose blow-off: The excessive pressure generated by the combustion gases will easily overcome the clamping force of the radiator hoses, causing them to blow off.
* Residual pressure: Because the combustion gases are trapped within the relatively sealed cooling system (minus the blown hose), the pressure will slowly dissipate but can remain significant for hours, especially if there isn't a significant leak elsewhere in the system. This is why you might still find pressure when you open the radiator cap hours later.
However, it's important to note: While a blown head gasket is a *likely* culprit, other issues can also cause similar symptoms. These include:
* Cooling system blockage: A severely restricted cooling system can build up excessive pressure.
* Faulty radiator cap: A faulty pressure cap might not release pressure properly, leading to build-up.
* Other leaks: A crack in the radiator or another leak in the system might not be immediately apparent, but could still cause pressure build-up in the radiator, albeit usually less extreme than with a blown head gasket.
In short: A blown head gasket is a very strong possibility given your description. However, a proper diagnosis requires a mechanic to investigate the cooling system thoroughly. Opening the radiator cap on a pressurized system is dangerous; always allow it to cool completely before doing so. You should have a qualified mechanic diagnose the problem to avoid further damage or injury.
