Fel-Pro 35991 Engine Coolant Thermostat Seal

Fel-Pro Thermostat Seal for Ford Applications

Fel-Pro 35991 is a premium engine coolant thermostat seal made from rubber for a precise sealing interface in the cooling system. It is built for Ford and Lincoln applications that require a 55 mm inside diameter, 58.5 mm outside diameter, and 3.5 mm thickness.

• Rubber construction for coolant sealing applications
• Inside diameter: 55 mm
• Outside diameter: 58.5 mm
• Thickness: 3.5 mm
• Premium grade type
• Part number: 35991

Application Coverage

Compatible with a wide range of Ford and Lincoln vehicles, including Fits 2011-2025 Ford F-150, N/A; Fits 2020-2025 Ford Explorer, N/A; and Fits 2020-2025 Lincoln Aviator, N/A. This part also fits Ford Bronco, Escape, Mustang, Ranger, Transit-150, Transit-250, Transit-350, Transit-350 HD, Edge, Fusion, SSV Plug-In Hybrid, Expedition, C-Max, and Lincoln Corsair, Nautilus, Continental, MKZ, MKX, and Navigator across the listed model years.

This part cross-references Ford BR3Z8255A and MAHLE C32675 for the same application.

What It Helps Address

• Coolant seepage at the thermostat sealing surface
• Loss of sealing integrity during thermostat service
• Improper fit from worn or damaged original seals
• Cooling system leaks that can affect temperature control

Installation Notes and Tips

Inspect the thermostat housing and mating surfaces before installation. Clean away old gasket material, coolant residue, and corrosion so the seal seats evenly. Verify the seal dimensions and application match the vehicle service requirements before reassembly.

Quality Assurance

Fel-Pro gaskets are engineered with application-specific materials to deliver vehicle sealing performance professionals rely on. The 35991 thermostat seal follows that approach with a premium rubber design for cooling system service.