Thermagasket Sealants

Welcome to the full lineup of Thermagasket Sealants by RX Auto—your trusted source for high-performance head gasket repair chemicals designed to restore engine reliability without the need for costly mechanical repairs. Whether you're dealing with overheating, coolant loss, or a confirmed head gasket failure, our Thermagasket sealants are engineered to deliver permanent sealing under extreme heat and pressure.

Each formula in the Thermagasket line is specifically crafted to target different vehicle types and performance demands. From our standard Thermagasket Plus—ideal for daily drivers—to our Extreme Duty version built for diesel engines and commercial vehicles, RX Auto offers a precise solution for your engine’s needs. Our Hybrid-Safe formula is designed for modern electric-assisted engines, while the specialized Northstar Kit addresses common failures in Cadillac V8 platforms.

All Thermagasket sealants are designed to integrate into a complete chemical repair system, especially when paired with our Cooling System Cleaner and proper application steps. They are safe for use in aluminum and cast iron blocks and compatible with all major coolant types.

Trusted by professional repair shops and experienced DIYers alike, Thermagasket sealants are rigorously tested, easy to apply, and built to outperform generic alternatives. Explore our full range below and find the right formula to help you stop leaks, restore performance, and get back on the road with confidence.