Dayco 87634 HVAC Heater Hose

Dayco Small I.D. Heater Hose 87634

Dayco 87634 is a Small I.D. Heater Hose built for HVAC heater circuit service where a dual inside diameter hose is required. Made from EPDM and finished in black, it provides the correct routing and connection sizes for select import and domestic applications, including Audi A6 Quattro, Audi S6, Ford Focus, Toyota 4Runner, Toyota Pickup, and Isuzu I-Mark fitments.

Key Features

• EPDM construction for heater hose service
• Dual I.D. hose design with 5/8 in. end 1 and 3/4 in. end 2
• Black finish for a clean OE-style appearance
• Meets SAE J20R3 Class D-1 and SAE J1684 Type EC specifications
• Direct-fit application coverage for select heater inlet, heater outlet, valve-to-heater, and pipe-to-engine locations
• Dayco 87634 part number for accurate ordering and replacement matching

Product Details

Dayco’s Small I.D. Heater Hose line focuses on replacement hoses for tight-diameter HVAC connections where the hose must transition between two different inside diameters. Part number 87634 uses EPDM rubber for heater-circuit duty and is specified as a dual I.D. hose, making it a practical replacement for vehicles that require a 5/8 in. connection on one end and a 3/4 in. connection on the other. This hose is listed for multiple positions, including right, left, heater inlet, heater outlet, valve to heater, heater to valve, pipe to thermostat, tee to water pump, pipe to engine, and heater to pipe. This part cross-references Gates 18749 for the same application.

Compatible vehicle coverage includes 2009-2011 Audi A6 Quattro, 2008-2011 Audi S6, 2000-2003 Ford Focus, 1993-1994 Chrysler Concorde, 1993-1994 Chrysler Intrepid, 1993-1994 Dodge Intrepid, 1988-1991 Toyota 4Runner, 1988-1991 Toyota Pickup, and 1981-1984 Isuzu I-Mark. If you are replacing a worn heater hose on an Audi A6 Quattro or Audi S6, Dayco 87634 provides the correct small I.D. configuration for the listed heater circuit locations.

Common Uses

• Replacing cracked or softened heater hose sections
• Restoring coolant flow through heater inlet and outlet lines
• Repairing leaks at valve-to-heater or heater-to-valve connections
• Addressing hose mismatch where two different inside diameters are required
• Servicing heater circuit routing on Audi A6 Quattro, Audi S6, Ford Focus, Toyota 4Runner, Toyota Pickup, and Isuzu I-Mark applications

Installation Notes

Verify the end diameters before installation: 5/8 in. on one end and 3/4 in. on the other. Match the hose to the listed position and route it to avoid kinks, abrasion, and contact with hot components. Drain and refill coolant as needed, then inspect the system for leaks after warm-up. Because this hose does not include a heat shield or protective sleeve, confirm that surrounding clearance and routing are correct for the vehicle.

Quality Assurance

Dayco 87634 is built to SAE J20R3 Class D-1 and SAE J1684 Type EC specifications for heater hose service. The EPDM construction and application-specific sizing support consistent replacement for the listed HVAC heater hose locations.