How to determine if the coolant hoses need to be replaced

What do coolant hoses do?

The coolant hose circulates the coolant throughout the engine. Coolant hoses are filled with a coolant mixture that absorbs the heat from the engine. After the heat leaves the coolant being pushed through the hose, the fluid recycles to the engine. A hose failure can cause an overheated engine, loss of power steering, and loss of the electrical charging system. If a hose leaks coolant, the engine overheats, which can lead to severe internal damages that require expensive repairs.

Radiator and Heater Hoses

The radiator is one of the most important parts of the vehicle because it keeps the engine at its nominal operating temperature, which is typically between 195 and 220 degrees Fahrenheit (90 and 105 degrees Celsius).

There are two main radiator hoses: an upper hose which connects the top of the radiator to the top of the engine, and a lower hose which connects the bottom of the radiator to the water pump of the engine.

There are also two smaller heater hoses which lead to and from the heater core located under the dashboard which passes heat to the interior of the vehicle.

Coolant Bypass Hoses and Pipes

Bypass hose is used to circulate the coolant through the engine, bypassing the radiator when the thermostat is closed. Bypass pipes are rigid, non-flexible tubes made of steel or plastic.

Bypass hoses are rubber compound hoses. The design of these coolant hoses and pipes varies from automaker to automaker, and is also known as a "fifth hose."

Overflow Hoses For The Reservoir Tank

A radiator overflow tank collects the expanding coolant that is heated by the engine and recycles it back into the coolant system once it loses enough heat. The radiator overflow tank works in conjunction with the radiator cap to protect the engine and prevent coolant loss due to overflow. The expansion tank has a hose which allows coolant to flow back into the radiator. It is essential to have enough coolant in the overflow and a working cap, otherwise, the air will draw into the system which doesn't dissipate heat well.

How do I know if my coolant hoses should be replaced

Coolant hoses are made of flexible, durable rubber compounds. They are designed to hold coolant under pressure, hoses are also subjected to fluctuating extremes of heat and cold, dirt, oils, and sludge. Unfortunately, over time, these hoses wear out, mostly because of electrochemical degradation. According to engineers for the Gates Corporation, a parts maker, ECD attacks hoses from the inside, causing tiny cracks. Acids and contaminants in the coolant can then weaken the yarn material that reinforces the hose. Sooner or later, pinholes can develop, or the weakened hose may rupture from heat, pressure, or constant flexing.

Coolant hoses also can get damaged outside because of direct contact with oil or other contaminants. For example, when hot oil drips onto the rubber from a leaky engine. Remember, hot coolant from within, excess engine compartment temperatures can degrade the rubber compounds. Due to this, small cracks appear on the rubber hose, or the hose can split and leak.

Protecting the cooling system hoses from wear

  • Check often the coolant tank to ensure proper fluid level. Do it when the engine is cold or hot. If even after topping off the coolant in the tank, the level is low, most probably there is a leak in the housing. Also check for white, light green, blue, or pink coolant tracks in the engine bay, which is residue left from leaking coolant.

  • Wait until the engine is cooled down, then squeeze each of the hoses in various spots. If the hose doesn't quickly return to normal shape after squeezing it, the rubber is in good condition, if the hose feels spongy or doesn't pop back, then the rubber is worn out and needs to be replaced.

  • Examine the hose for cracks and splits on the outside. If you see any oil contamination on the outside of a hose, clean it off and feel the rubber. If any mushy spots exist, the hose has become severely weakened.

  • Look for parallel cracks around bends (caused by ozone), a hardened glassy surface (heat damage), or abrasive damage (hose is rubbing).

  • Flush and replace the coolant (check the owner's manual).

Never remove the radiator cap when the engine is hot, as the hot coolant will be under pressure.

TIP: The upper radiator hose fails more often than any other hose, followed by the water pump bypass hose, and the outlet heater hose from the engine to the heater core. Experts recommend that all hoses need to be replaced at least every four years or when one fails.