Dorman 926-391 4WD Vacuum Check Valve

4WD Vacuum Check Valve Overview

Dorman 926-391 is a 4WD vacuum check valve built to match the original valve’s fit and function in the vacuum-operated 4WD system. It helps maintain proper vacuum levels for the 4WD hub lock circuit on select Ford and Lincoln trucks and SUVs, including Ford F-150, Expedition, Lincoln Navigator, and Mark LT applications.

• OE-style replacement for the factory 4WD vacuum check valve
• Black EPDM construction for vacuum system use
• Round connector shape with 3-port design
• Overall length: 17 in.
• Outer diameter: 0.39 in. (10 mm maximum diameter)
• Port sizes: 5 mm, 5 mm, and 3 mm
• Fits 2010-2017 Ford Expedition, N/A, 4WD Vacuum Hub Lock
• Fits 2010-2017 Lincoln Navigator, N/A, 4WD Vacuum Hub Lock
• Fits 2010-2014 Ford F-150, N/A, 4WD Vacuum Hub Lock
• Fits 2010-2014 Lincoln Mark LT, N/A, 4WD Vacuum Hub Lock

Detailed Product Description

This Dorman 926-391 4WD vacuum check valve is engineered to restore the original routing and retention of vacuum in the 4WD hub lock system. It is a direct-fit style replacement for vehicles that rely on vacuum control to engage or release the front hub locking system. This part cross-references OE numbers AL3Z3A788A and BL3Z3A788A for the same application.

Common Problems This Part Can Address

• Loss of vacuum pressure in the 4WD hub lock circuit
• Delayed or inconsistent front hub engagement
• Vacuum bleed-down after engine shutdown
• Faulty check valve operation in the vacuum line
• 4WD system performance issues related to vacuum routing

Installation Notes and Tips

Verify the vehicle’s vacuum line routing and connector sizes before installation. Confirm the replacement valve matches the original port layout, outer diameter, and overall length for proper fit. For best results, inspect nearby vacuum hoses and fittings for cracks, hardening, or leaks while servicing the system. Compatible With 2010-2017 Ford Expedition, 2010-2017 Lincoln Navigator, 2010-2014 Ford F-150, and 2010-2014 Lincoln Mark LT equipped with 4WD Vacuum Hub Lock.

Quality Assurance

Dorman designs this replacement valve to match the fit and function of the original component, supporting reliable service in the vehicle’s vacuum-operated 4WD system.