Silicone Heater Hoses

The best heater hose for automotive use is one that matches the vehicle’s required inside diameter, coolant compatibility, operating temperature, pressure rating and routing shape. For ordinary passenger car, light truck, restoration and custom cooling applications, an SAE 20R3 EPDM heater hose is a practical choice when its ratings meet the vehicle requirements.

Evil Energy straight EPDM hoses are specified for coolant, water and antifreeze, with temperatures from 40°F below zero to 257°F and working pressure up to 100 PSI, depending on the product and size. A universal straight hose should not replace an OE molded or branched assembly if it must be bent sharply to fit.

Choose a heater hose replacement by its nominal inside diameter. Read the ID printed on the original hose or measure the outside diameter of the clean fitting barb. Do not order by the old hose’s outside diameter because wall thickness varies.

Common heater circuit sizes include 5/8 inch heater hose and 3/4 inch heater hose, while 5/16 and 3/8 inch sizes are often used for smaller coolant, bypass or overflow connections. A 3 inch silicone hose is not an appropriate substitute for the products in this collection, which range from 5/16 inch to 1 inch. Also confirm the required length, minimum bend radius and whether the original connection uses a barb, molded end or quick connector.

A purpose built silicone coolant hose may offer a higher temperature range than some rubber hoses, but its actual performance depends on its reinforcement, wall construction and published pressure rating. EPDM heater hose is widely used for automotive coolant because EPDM resists coolant, heat, ozone and weather exposure.

The products currently offered by Evil Energy in this range are EPDM, not silicone. Neither material should be assumed suitable for every fluid. These hoses are specified for coolant, water and antifreeze, so use a purpose rated fuel or oil hose for fuel, engine oil or transmission fluid.

Only begin a heater hose replacement when the engine and cooling system are fully cold. Drain enough coolant to place the hose connections above the fluid level, remove the old hose and clamp, clean and inspect the fitting, then route the replacement without twisting, kinking or exceeding its minimum bend radius.

Push the hose fully over the fitting bead and position the clamp squarely behind that bead. Keep the hose away from exhaust components, belts, pulleys and sharp edges. Refill with the vehicle specified coolant, bleed trapped air according to the service manual, warm the engine and inspect every connection for leakage. Do not continue if a heater core tube or plastic fitting is cracked or heavily corroded.

Inspect a coolant hose for visible cracks, swollen sections, bulges, abrasion, coolant residue and leakage near the clamps. A hose that feels unusually soft, spongy, hardened or brittle may also be deteriorating internally. Other warning signs include a sweet coolant smell, falling coolant level, inconsistent cabin heat or an increasing engine temperature.

Inspect only when the engine is cold. Gates also recommends checking for soft spots, cracks near the hose ends and bulges in its official coolant hose inspection guidance. Replace a damaged hose before it progresses into a coolant loss or overheating event.