Car radiator hoses are the two flexible tubes that circulate coolant from the engine to the radiator, where it is cooled, then back to the engine. There are two types of radiator hoses: moulded and flexible. Radiator hoses are constructed from silicone rubber, neoprene and other synthetic materials, and are designed for long service life. Nevertheless, conditions develop that may cause them to collapse or fail altogether.
Clogged Cooling System
A collapsed radiator hose does not necessarily indicate a bad hose. Build-up of chemical deposits or debris in the cooling system will gradually constrict coolant flow. This and other coolant blockages can cause system overheating and a vacuum sufficient to collapse a weakened hose.
Faulty Radiator Cap
Radiator caps are designed to maintain cooling system pressures in the range of 12 to 15 PSI. When an engine is shut down, the coolant temperature begins to drop. If the vacuum valve in the radiator cap fails, the resulting vacuum in the cooling system can cause a radiator hose to collapse. A malfunctioning radiator cap can also constrict coolant flow. When this happens, the water pump, trying to draw coolant through the lower radiator hose, can create a vacuum sufficient to collapse the hose.
Radiator hoses are designed to withstand high pressures and temperatures ranging from -40 degrees Fahrenheit to over 121 degrees C. They must also resist chemical attack by coolants and other materials, such as oil and mud, tar and road debris, salt and ozone. Radiator hoses deteriorate with age, a process that occurs primarily from the inside out. Surface oil accelerates breakdown of the material. Surface cracks develop which cause hoses to split, blister or leak. They become hard and brittle and will eventually weaken and fail.
Faulty or Missing Wire Reinforcement
Some radiator hoses have an inner reinforcing coil or wire reinforcement. If it is missing or damaged, the lower radiator hose could collapse at high vehicle speeds, thereby constricting or cutting off coolant flow to the engine. A collapsed hose will often resume its normal shape when the engine slows down or is turned off.
Electro-chemical Degradation (ECD)
Modern engines and radiators can create conditions that generate electrical currents in the coolant and on the inner surfaces of coolant hoses. These currents create pits, cracks and striations in hoses, effects that eventually cause them to weaken and fail. ECD can often be identified by pinching a hose at the ends. Radiator hoses should be examined regularly. They should be replaced every five years or when there is evidence of significant wear or damage.