• Check the hose condition.
  • Hoses are normally firm, yet flexible.
  • Check carefully for chafing and swelling.
  • Look for leaks, stiffness, sponginess, hidden rot, rubbed or burned areas, and oil soaking. Hoses that appear to be cracked, swollen, hard, soft or broken should be replaced.
Defects in hoses.
  • When checking hoses for hardness try to bend them, especially at the ends.

Be careful when bending a hose at the end. A bad hose might break, allowing dangerous fuel or hot, pressurized coolant to escape.

Sometimes cutting off the first end of hose will eliminate a hardened section.
  • Also change any hose that feels mushy or extremely brittle when firmly squeezed.
  • Be especially watchful for signs of splits when hoses are squeezed. These splits have a habit of bursting wide open under pressure.
  • Also look for rust stains around the clamps. Rust stains indicate the hose is leaking, possibly because the clamp has eaten into the hose. Loosen the clamp, slide it back, and check for cuts.
  • Do not overlook the small by-pass hose on some models. It is located between the water pump and engine block. Also, check the lower radiator hose very carefully.
  • This hose contains a coiled wire lining to keep it from collapsing during operation. If the wire loses tension, the hose can partially collapse at high speed and restrict coolant flow. This results in a very elusive overheating problem.

Oil Damage

Rubber hoses that are not used in fuel- or oil-related environments can deteriorate rapidly when they come into contact with oil. Oil, an enemy of rubber hoses, can cause them to swell. Be sure to fix any oil leaks. Also, water pump lubricants found in some cooling system additives contain petroleum, which can damage the inside of the hose.

Defective hoses do not always outwardly appear so. Deteritoration on the inside of the hose can cause small particles to flake off and fall into the coolant.

Check the rubber on the inside of the hose to see that it is not deteriorating. Occasionally, a relatively low-mileage vehicle will experience the failure of a hose that appears to be good on the outside.

Electrochemical Damage and Radiator Hoses

A newly discovered condition discovered independently by both Gates and Goodyear has been found to lead to hose failure. It is usually called electrochemical degradation or ECD. ECD occurs when the hose, engine coolant, radiator, engine, and fittings form a galvanic cell, or battery. This causes small cracks in the inside of the hose, allowing coolant to penetrate into the hose reinforcement. New coolant hose that is electrochemically resistant is made of ethylene propylene rubber or EPDM (ethylene propylene diene monomer).

To check for ECD damage, squeeze the hose in several places to see if the rubber has the same consistent feel throughout. Be sure to thoroughly check both hoses. The upper radiator hose (engine outlet end) suffers that most abuse because it is exposed to fully heated coolant before it reaches the radiator. Lower hoses, on the other hand, are more difficult to inspect and are often overlooked.

Some lower radiator hoses have a coil of wire in them. The coil is installed at the factory so that the hose does not collapse during the factory coolant fill procedure. A rusty cooling system will often result in pieces breaking off and circulating in the system. If the wire is missing, coolant circulation, especially at highway speeds, can be hampered. Whenever one of these hoses is removed during service, check to see that the wire is not rusted.