Dayco 86503 Engine Coolant Reservoir Hose

Dayco Small I.D. Heater Hose 86503

Dayco 86503 is a Small I.D. Heater Hose built for coolant routing in a range of import and domestic applications. Made from EPDM and finished in black, it uses a single I.D. hose design with 9/32-inch inside diameter at both ends for direct replacement in the specified positions.

Compatible With Toyota Tacoma, Honda Odyssey, Acura TL, Acura TSX, Honda Pilot, and other listed applications, this hose is used in heater and coolant transfer paths such as reservoir to pipe, pipe to throttle body, and pipe to engine. The Dayco Small I.D. Heater Hose line is intended for vehicles that need a compact-diameter coolant hose with SAE J20R3 Class D-1 and SAE J1684 Type EC compliance.

Key Features

• Brand: Dayco
• Part number: 86503
• EPDM construction for coolant-system service
• Black finish for OE-style appearance
• Single I.D. hose with 9/32-inch inside diameter at both ends
• Meets SAE J20R3 Class D-1 and SAE J1684 Type EC specifications
• Small I.D. Heater Hose line for compact coolant routing

Detailed Description

Dayco 86503 is an engine coolant reservoir hose / small I.D. heater hose designed for vehicles that use a narrow coolant line between components. Its EPDM rubber construction is suited for heater and coolant circulation service, while the 9/32-inch end diameters support the listed OE-style routing points. This part number is commonly searched for Toyota Tacoma coolant hose replacement, Honda Odyssey reservoir to pipe hose replacement, and Acura TL pipe to throttle body hose applications.

This part cross-references Gates 18176 for the same application.

Common Issues This Hose Can Address

• Cracked or hardened small-diameter coolant hose
• Coolant seepage at a reservoir-to-pipe connection
• Heat-related hose deterioration in throttle body coolant routing
• Loss of flexibility in an aging EPDM hose
• Replacement needs for a cut-to-fit small I.D. heater hose application

Installation Notes and Tips

• Verify the vehicle position and hose routing before installation.
• Some listed applications require the hose to be cut on both ends for proper length and fit.
• Confirm the 9/32-inch inside diameter matches the original hose connection points.
• Inspect adjoining pipes, tees, and clamps for wear before reassembly.
• Use the fitment notes for exact routing, such as reservoir to pipe, pipe to throttle body, or pipe to engine.

Quality Assurance

Dayco manufactures this hose to SAE J20R3 Class D-1 and SAE J1684 Type EC specifications for coolant-system service. The EPDM construction and application-specific fitment support consistent replacement for the listed vehicles, including Toyota Tacoma, Honda Odyssey, and Acura TL.