RTV Silicone
Room Temperature Vulcanizing silicone sealant used to create form-in-place gaskets for engine and drivetrain covers.
RTV (Room Temperature Vulcanizing) silicone is a specialized liquid or paste sealant widely used in automotive repair to create flexible, form-in-place gaskets. RTV cures into a tough, rubbery seal when exposed to moisture in the air at room temperature. It is used to seal mating surfaces on oil pans, valve covers, timing covers, thermostat housings, and differential covers.
RTV comes in various formulations tailored for specific environments: ultra-grey (high torque and vibration resistance, common for import engines), ultra-black (maximum oil resistance), and red (high-temperature resistance for exhaust flanges). RTV is often used to supplement pre-formed gaskets, particularly at joint corners (such as where a timing cover meets the engine block and oil pan), to prevent oil leaks.
Proper application of RTV requires cleaning the mating surfaces with solvent to remove all oil and grease. A continuous bead is applied around the mating flange, circling the bolt holes. The components are bolted together finger-tight until the silicone begins to squeeze out, left to set for an hour, and then torqued to spec. The sealant must cure fully (typically 24 hours) before fluids are reintroduced.