Permatex High-Temp Red RTV Silicone Gasket Maker, 11 oz — Engine & Transmission Sealant, Sensor-Safe to 650°F

Permatex 81409 High-Temp Red RTV Silicone Gasket Maker is an 11 oz formed-in-place silicone sealant engineered to create durable gaskets that withstand extreme heat and shop fluids.

Designed for heavy-duty automotive and industrial use, this red RTV silicone replaces or upgrades cut gaskets and coats pre-cut gaskets to improve long-term reliability. The formula was developed for applications exposed to repeated thermal cycling, towing loads, and contact with oils and coolants. It’s temperature-rated from -65°F up to 650°F intermittent, making it suitable for many engine and transmission sealing jobs.

How does this gasket maker perform under high temperatures and thermal cycling?

Permatex 81409 uses a hi-temp silicone formulation that resists cracking, shrinking, and migration when subjected to rapid temperature changes. It maintains torque retention on fasteners and preserves sealing integrity under sustained heat, reducing the need for frequent rework.

• Temperature range: -65°F to 650°F intermittent (-54°C to 343°C)
• Resists cracking and shrinking from repeated heating and cooling
• Designed for continuous exposure to engine and shop fluids

Where should I use this red RTV silicone in my vehicle or equipment?

This product is intended for a wide array of engine and drivetrain sealing points where high temperature resistance and fluid compatibility are required. It works well on both OEM and aftermarket materials, including aluminum, bi-metal alloys, and many plastics used in modern components.

• Valve covers, oil pans and timing covers
• Water pumps and thermostat housings
• Transmission pans and other heavy-duty applications

Will Permatex 81409 replace a pre-cut gasket, and how should it be applied?

Yes — it can replace most cut gaskets by forming a reliable in-place seal, or it can be applied over an existing gasket for added protection. For best results, surfaces should be clean, dry, and free of old gasket residue; apply a continuous bead and allow proper cure time before pressurizing or restarting the engine.

• Remove old gasket material and clean surfaces
• Apply continuous bead; assemble within manufacturer-recommended squeeze-out guidelines
• Allow full cure before exposing to fluids or operating temperatures

Is this product compatible with sensors, modern materials, and shop fluids?

Permatex 81409 is formulated to be sensor-safe and to perform on modern component materials common in current vehicles and equipment. It resists degradation when exposed to motor oil, transmission fluid, antifreeze, and common workshop chemicals.

• Sensor-safe formulation suitable for many engine sensors
• Resists oil, coolant, and typical shop fluids
• Compatible with aluminum and many plastics and alloys

Who is this for: Permatex 81409 High-Temp Red RTV Silicone is aimed at professional mechanics, fleet maintenance teams, and DIY enthusiasts who need a reliable, heat-resistant formed-in-place gasket solution. It’s especially useful for heavy-duty and high-temperature applications such as towing, racing, restoration projects, and any repair where long-term sealing and fluid resistance are priorities.