2Pcs High Temperature 4-Ply Reinforced Silicone Hose Cap ID

TuoLauthon 2-pack reinforced silicone hose caps are high-temperature, 4-ply plugs designed to seal 5/16" (8mm) ports for turbo bypass valves, throttle-body water ports, heater cores and other coolant or vacuum lines.

These compact silicone end caps combine thick-wall, polyester reinforcement with stainless clamps so you can temporarily cap or permanently seal small-diameter coolant and vacuum ports without cutting or welding. Each cap fits hoses with a 5/16" internal diameter, resists heat up to 350°F, and arrives as a set of two caps plus two rust-resistant clamps for an immediate install on cars, trucks, and motorsport plumbing.

Will these silicone caps withstand engine bay temperatures?

Yes — the caps are built from 4-ply polyester-reinforced silicone formulated for elevated heat and pressure. The material maintains shape and sealing performance under typical engine cooling-system temperatures and brief higher peaks.

• Maximum rated temperature: 350°F (177°C).
• 4-ply polyester reinforcement for stability under pressure.
• 5mm wall thickness reduces collapse or blow-off risk.
• Stainless steel clamps included for secure fastening.

What size ports and hoses do these plugs fit?

Each cap is sized for a 5/16" (8mm) internal diameter hose end; the outer diameter and overall lengths are optimized for common small coolant and vacuum ports. The dimensions make them suitable for many turbo bypass, heater bypass, and throttle-body water fittings.

• Inner diameter (ID): 5/16" (8mm).
• Outer diameter (OD): 45/64" (approx. 18mm).
• Inside length: 4 cm; overall length: 4.5 cm for a snug fit.
• Wall thickness: 5 mm for durable sealing contact.

How do I install and secure the hose caps?

Installation is straightforward: slide the cap over the hose or port and tighten the supplied stainless-steel clamp until the silicone compresses evenly. The clamp provides a reliable mechanical seal while the reinforced silicone offers flexibility to accommodate slight variations in port shape.

• Push cap onto hose end or port opening until seated.
• Position stainless clamp over cap lip and tighten with a screwdriver or nut driver.
• Confirm no visible gaps and that the clamp is snug but not over-tightened.
• Re-check after a short test run for any loosening under heat cycles.

Are there any fluids or conditions to avoid with these plugs?

These silicone caps are engineered for water, coolant, air and vacuum applications; they are not compatible with oil, gasoline, diesel or other petroleum-based fluids. Avoid prolonged exposure to aggressive chemicals and fuels that degrade silicone or the polyester reinforcement.

• Recommended: coolant, water, compressed air, vacuum, turbo bypass ports.
• Not compatible: oil, gasoline, diesel, and petroleum-derived fluids.
• Avoid prolonged contact with harsh solvents or acids.
• Inspect periodically for wear if used in high-cycle or high-vibration environments.

Who is this for? If you work on performance engines, repair heating and cooling systems, or need a reliable way to block small-diameter ports temporarily or permanently, these TuoLauthon silicone hose caps offer a low-cost, high-temperature sealing solution. They suit home mechanics, tuners, fleet maintenance techs, and DIYers who need an easy install with corrosion-resistant clamps and heavy-duty reinforcement. Note: choose different specialty plugs for petroleum-based fluids or larger hose diameters.