* The hose is old and brittle. As rubber ages, it loses its flexibility and becomes more brittle. This can cause the hose to become hard and crack under pressure.
* The hose is clogged. If the hose is clogged with debris, it can restrict the flow of coolant and cause the hose to become hard under pressure.
* The hose is kinked. If the hose is kinked, it can restrict the flow of coolant and cause the hose to become hard under pressure.
* The engine is overheating. If the engine is overheating, it can cause the pressure in the cooling system to increase, which can cause the hose to become hard under pressure.
If you notice that your radiator hose is becoming hard under pressure, it is important to have it inspected by a mechanic to determine the cause. If the hose is old and brittle, it should be replaced. If the hose is clogged, it should be cleaned or replaced. If the hose is kinked, it should be straightened out. If the engine is overheating, the source of the overheating should be addressed.
