LO 11-8 Outline maintenance procedures and identify tools and methods used to perform maintenance on a diesel engine cooling system

Hose Inspection
Air, coolant chemical attacks, and extreme temperatures all contribute to hose deterioration. As hoses age, they can become hardened and crack. Electrochemical attacks on hoses tend to affect the hoses nearest to the radiator and engine ends. Internally, hoses can soften and crack, causing lining failure and eventual hose rupture. Rubber particles loosened from the hose linings can clog radiators and thermostats. A weakened hose may collapse and restrict coolant flow. When checking the lower radiator hose, it is important to verify that the hose has not been incorrectly repaired in such a way that it would allow the hose to collapse during rapid water pump acceleration. If the radiator is restricted, a very low-pressure area is created between the pump and the radiator. Once collapsed, the hose may completely restrict coolant flow in a running engine. To prevent a hose collapse, lower radiator hoses are often made of tubular sheet metal with flexible couplers at the engine and radiator. The bottom radiator hose may also have an internal coiled spring that prevents the hose from collapsing when the engine is suddenly accelerated and the water pump draws more coolant.

The following is a recommended procedure to inspect coolant hoses for the effects of electrochemical degradation (ECD):

1. Make sure the engine is cool.
2. Use fingers and thumb to partially squeeze the hose near the clamps, or connectors, while checking for weakness. Do not use your whole hand. ECD usually occurs within 2" of the ends of the hose and not in the middle. Do not completely squeeze the hose, as too much compression can crack the inside of the hose.
3. While squeezing, feel for voids, cracks, mushiness, or weak spots near the hose ends. The heaviest damage occurs where the temperature is the hottest and air is present with the coolant. Upper radiator hoses more commonly fail first.