Gates 21603 Radiator Coolant Hose - Upper

Gates 21603 Molded Coolant Hose Overview

The Gates 21603 molded coolant hose is a radiator coolant hose built to OEM-quality specifications for upper cooling-system service. Made from EPDM, it provides the formed shape needed for direct routing in the engine bay on select Chevrolet Astro, GMC Safari, and Chevrolet Camaro applications.

Gates Molded Coolant Hose products are built as application-specific replacement hoses for upper, lower, bypass, heater, and other coolant circuits. This line is engineered to simplify radiator hose replacement by matching the original hose form and fit requirements for the vehicle.

Key Features

• Part number: 21603
• Brand: Gates Molded Coolant Hose
• Radiator coolant hose for upper hose applications
• EPDM construction for coolant-system service
• Molded design for formed routing
• End 1 inside diameter: 1.25 in. (32 mm)
• End 2 inside diameter: 1.25 in. (32 mm)
• Centerline length: 24.8 in. (630 mm)
• No spring and no quick-connect fittings

Detailed Description

Gates 21603 is a molded radiator coolant hose intended for upper cooling-system routing where a formed hose profile is required. The EPDM material is selected for coolant exposure, while the molded shape helps match the original hose path and connection points. This makes it a practical replacement for vehicles that need a direct-fit upper coolant hose rather than a universal straight hose.

Compatible With 1987-1990 Chevrolet Astro, upper; 1987-1990 GMC Safari, upper; and 1985-1989 Chevrolet Camaro, upper. For fitment searches, this part is commonly referenced as Gates 21603 radiator coolant hose for Chevrolet Astro upper hose replacement and GMC Safari upper coolant hose replacement.

This part cross-references Dayco 71189 for the same application.

Common Problems This Hose Can Address

• Cracked or hardened upper radiator hose material
• Coolant leaks at the hose body or connection ends
• Incorrect hose routing from a previous repair
• Collapsed or misshaped hose sections on formed applications
• Replacement needs for radiator and HVAC-compatible coolant and heater hose routing on select Astro and Safari models

Installation Notes and Tips

Verify the hose shape, end diameters, and centerline length against the original part before installation. Inspect adjoining necks, clamps, and coolant passages for wear or corrosion, and confirm the routing matches the vehicle’s upper hose path. Drain coolant as needed before removal, then refill and bleed the cooling system according to the vehicle service procedure.

Quality Assurance

Gates manufactures this molded coolant hose to OEM-quality specifications for replacement use in the cooling system. The molded construction and application-specific dimensions support accurate fitment on the listed Chevrolet and GMC vehicles.