Dayco 87941 Engine Coolant Bypass Hose

Dayco Small I.D. Heater Hose for Mazda 3

Dayco 87941 is an engine coolant bypass hose built for Mazda 3 and Mazda 3 Sport applications that require a small I.D. heater hose with dual inside diameters. Made from EPDM rubber with a black finish, it is shaped for coolant routing where a stepped hose connection is needed. The Dayco Small I.D. Heater Hose line focuses on direct-fit cooling system hose replacements for specific vehicle applications.

Key Features

• EPDM construction for coolant system service
• Dual I.D. hose design with 5/8 in. and 11/16 in. inside diameters
• Protective sleeve included for added abrasion resistance
• Black hose finish for OE-style appearance
• Built to SAE J20R3 Class D-1 and SAE J1684 Type EC specifications
• Cross-references Mazda LF8N-15-260A and Duralast E87941

Detailed Description

This Dayco engine coolant bypass hose is engineered for 2010-2013 Mazda 3 and 2010-2013 Mazda 3 Sport applications listed below. Part number 87941 uses a dual I.D. layout to match the stepped coolant connection found in these vehicles, helping maintain proper hose routing in the heater and bypass circuit. The EPDM rubber construction is suited for hot coolant service, while the protective sleeve adds an extra layer where the hose passes near surrounding components. If you are replacing a worn or leaking small I.D. heater hose on a Mazda 3, Dayco 87941 provides a direct replacement option for the specified fitments.

Compatible With 2013 Mazda 3, N/A. Compatible With 2010-2011 Mazda 3, N/A. Compatible With 2012-2013 Mazda 3 Sport, N/A. Compatible With 2010 Mazda 3 Sport, N/A.

Common Repair Symptoms

• Coolant seepage at the heater hose connection
• Cracked, hardened, or swollen hose material
• Loss of coolant from the bypass circuit
• Soft or deteriorated hose ends at the stepped connection
• Visible wear where the hose routes near nearby components

Installation Notes and Tips

Verify the inside diameters before installation to confirm the stepped connection matches 5/8 in. and 11/16 in. ends. Inspect adjoining clamps, fittings, and coolant passages for corrosion or residue before installing the new hose. Route the hose to match the original path and confirm the protective sleeve is positioned where contact or heat exposure is most likely.

Quality Assurance

Dayco 87941 is manufactured to SAE J20R3 Class D-1 and SAE J1684 Type EC standards for heater and coolant hose service. The Dayco Small I.D. Heater Hose line is built for application-specific cooling system replacement on listed Mazda models.