Gates 31391 Radiator Cap Tester Adapter

Radiator Cap Tester Adapter for Cooling System Service

The Gates 31391 radiator cap tester adapter is used with a radiator cap and cooling system tester to service multiple component sizes. This 50mm O.D. threaded cap adapter helps technicians connect the tester to the correct cap style for accurate cooling system checks on a wide range of vehicles, including Chevrolet Silverado, GMC Sierra, and Cadillac applications.

Key Features

• Cap adapter for use with a radiator cap and cooling system tester
• 50mm O.D. threaded design
• Attachment type: cap adapter
• Built for multi-size cooling system testing applications
• Gates part number 31391

Product Details

Gates Radiator Cap/Cooling System Tester Adapter 31391 is a service tool adapter made to interface with a radiator cap and cooling system tester when the vehicle uses a 50mm outer diameter threaded cap connection. The Gates 31391 adapter supports accurate pressure testing by helping the tester engage the correct cap interface during diagnosis. This part cross-references Dorman - HELP 46826 for the same application.

Compatible With select 1999-2019 Cadillac, Chevrolet, Buick, GMC, Dodge, Jeep, Ram, Mazda, Pontiac, Saturn, Suzuki, Saab, Hummer, Isuzu, and Oldsmobile models. Common fitment includes Fits 2017-2018 Chevrolet Silverado 2500 HD, N/A; Fits 2017-2018 GMC Sierra 3500 HD, N/A; and Fits 2016-2019 Cadillac CT6, N/A. The part number 31391 is also listed for multiple GM cooling system service applications across cars, trucks, vans, and SUVs.

What This Adapter Helps Diagnose

• Cooling system pressure loss during radiator cap testing
• Improper cap-to-tester connection on 50mm threaded caps
• Radiator cap sealing concerns during service checks
• Pressure test setup issues on supported GM and other listed vehicles
• Cooling system inspection on Chevrolet Colorado, GMC Canyon, and similar applications

Installation Notes and Tips

Use this adapter only with a compatible radiator cap and cooling system tester. Confirm the cap style and 50mm O.D. threaded specification before testing. For best results, match the adapter to the vehicle’s cap connection and verify a secure seal before applying pressure. Always follow the tester manufacturer’s procedure and the vehicle service manual for cooling system diagnosis.

Quality Assurance

Gates supplies service components and diagnostic adapters used in professional cooling system testing. Part 31391 is built for radiator cap tester use and is listed with broad vehicle coverage for service bay applications.