LO 11-6 Identify and describe the construction features, types, and applications of the diesel engine cooling components

Coolant Hoses, Hose Seals, and Hose Valves
The upper and lower radiator hoses and heater hoses require flexible connections between the engine radiator and the heater core due to engine vibration and torque flexion. These hoses must be able to withstand the hot under-hood environment as well as up to 40 psi (2.7 bar) or more of internal coolant pressure. Because cooling systems operate under a wide range of temperatures, hoses must be compatible with operating conditions from well below zero to over 250° F (121° C) without failing. A silicone-based material and an ethylene propylene rubber compound known for its resilience and flexibility are two common hose materials. Silicone-based hoses are more chemically resistant to deterioration and are able to withstand wider temperature variations, which makes them premium quality. Silicone hoses, however, are generally not compatible with oil and will soften if exposed to fuel and lubrication oil. Also, silicone hoses are not compatible with all types of long-life antifreeze either, particularly some OATs, and may quickly deteriorate if the wrong type of coolant is used.

Hose clamps help the hose seal at its connections. Constant-torque spring clamps allow hose ends to thermally expand and contract, which minimizes coolant loss from loose clamps Figure 58. Some vehicles are manufactured with shrink bands, which perform like electrical shrink tube instead of hose clamps. Shrink bands are designed to prevent cold-weather leaks, and they do not require any adjustment after installation. These bands are not reusable and are cut off an engine hose during service.

MD vehicles are increasingly using an electrically operated, three-way coolant control valve instead of a coolant bypass passageway. The purpose of a three-way control valve is to open or close coolant flow to the heater core. By shutting off coolant flow to the cab heater core when only the air-conditioning (A/C) is demanded or when the engine is warming up, the engine warm-up time is shortened. Because warm coolant flow is not directed to the cab, warm-up time is shortened to reduce fuel consumption and GHG emissions Figure 59.

FIGURE 11-58: Constant-torque hose clamps use a spring to maintain continual torque around the hose clamp. Tightening the clamp increases the torque applied continually by the clamp. A spring hose clamp uses spring pressure to maintain a continual pressure. Tension is not adjustable.

FIGURE 11-59: An electrically operated three-way valve controls the direction of coolant flow through the radiator and engine block or the block and heater core. The valve helps speed up engine warm-up.