Fel-Pro 35921 Engine Coolant Thermostat Seal

Fel-Pro 35921 Engine Coolant Thermostat Seal

Fel-Pro 35921 is an engine coolant thermostat seal built for direct-fit sealing performance in a wide range of Hyundai and Kia applications. It uses application-specific materials and precise dimensions to help maintain a reliable coolant seal where the thermostat housing meets the engine.

Compatible with Hyundai Tucson, Sonata, Santa Fe, Santa Fe Sport, Genesis Coupe, Veloster N, and Kia Sportage, Optima, Sorento, Stinger, Forte, Forte Koup, Forte5, Rondo, and Magentis applications across model years 2009-2021.

Key Features

• Fel-Pro part number 35921
• Premium grade thermostat seal for cooling system service
• Thickness: 5.3
• Inside diameter: 53.7 x 56.9
• Outside diameter: 59.5 x 62.7
• Application-specific sealing material for accurate fitment
• Cross-references MAHLE C32408 and C32409 for the same application

Detailed Description

Fel-Pro 35921 is an engine coolant thermostat seal engineered for vehicles that require a precise thermostat housing seal to maintain cooling system integrity. The premium-grade construction and measured dimensions help support a consistent seal surface, which is important when servicing the thermostat area on Hyundai Tucson, Hyundai Sonata, Kia Optima, Kia Sorento, and related models. Fel-Pro gaskets are known for vehicle-specific sealing solutions, and this thermostat seal follows that approach with materials selected for the application.

This part number 35921 is used in a broad range of Hyundai and Kia platforms from 2009 through 2021, making it a practical replacement choice when the original thermostat seal is worn, flattened, or no longer sealing correctly.

What It Helps Address

• Coolant seepage at the thermostat housing
• Sealing issues after thermostat service
• Loss of coolant from a deteriorated thermostat seal
• Improper sealing caused by an aged or compressed gasket
• Cooling system leaks at the thermostat interface

Installation Notes and Tips

Clean the sealing surfaces thoroughly before installation and inspect the thermostat housing for corrosion, pitting, or debris that could affect the seal. Verify the seal dimensions and application match before assembly. For best results, follow the vehicle service procedure for the specific Hyundai or Kia model being repaired.

Quality Assurance

Fel-Pro focuses on application-specific sealing materials and vehicle-level sealing performance. Part number 35921 is built as a premium thermostat seal for direct replacement use in confirmed Hyundai and Kia applications.