Engine Coolant Thermostat Housing Seal (35720) by Fel-Pro®. If you are looking for quality sealing solutions, Fel-Pro offers you various replacement products from seals and bolts to O-Rings and dowel pins. Engineered using the latest technologies and global engineering resources, Fel-Pro parts meet specific OEM needs and provide superior sealing performance and durability needed to withstand the unique characteristics of the application.