Common Issues & Fixes for Plastic-to-Silicone Connections in L5P Duramax EGR Deletes

A frequent failure point in 2017–2019 L5P Duramax EGR delete kits is the connection between plastic fittings and silicone hoses, often resulting in coolant leaks or hose blow-offs under boost pressure (20+ psi). Below are the root causes and proven solutions to ensure a reliable seal.

Common Failure Points

1. Silicone Hose Slippage
   • Many kits use low-cost silicone hoses clamped onto plastic coolant fittings.
   • Under high boost, unreinforced hoses (e.g., 2-ply) can expand and detach, leading to leaks.
2. Plastic Fitting Degradation
   • OEM or low-quality plastic fittings warp or crack from heat cycles and clamping stress.
   • Thin-walled aftermarket fittings are especially prone to failure.
3. Inadequate Clamping
   • Worm-gear clamps often apply uneven pressure, allowing hoses to loosen over time.
   • Overtightening can crack plastic fittings or cut into silicone hoses.
4. Thermal Expansion Mismatch
   • Silicone expands more than metal or rigid plastics, increasing separation risk under heat.

Reliable Solutions

✅ Upgrade Clamps – T-bolt clamps provide uniform pressure and resist boost-induced slippage better than worm-gear clamps.

✅ Reinforced Silicone Hoses – Use 4-ply or 5-ply hoses (e.g., Gates or Vibrant) to prevent expansion under boost.

✅ Metal Fittings – Replace plastic with billet aluminum or CNC-machined fittings (Kennedy Diesel/Sinister Diesel) for durability.

✅ Installation Best Practices

• Clean and dry mating surfaces before assembly.
• Apply hairspray or rubber adhesive to the fitting for a tackier seal.
• Double-clamp critical connections for redundancy.

Recommended Upgrades

• Coolant Reroute Fittings: Kennedy Diesel or Sinister Diesel billet aluminum kits.
• Hoses: High-temperature, reinforced silicone (4-ply minimum).

Final Recommendation

If leaks persist, the plastic fitting is the weak link—switching to metal fittings is the most durable fix. For a permanent solution, consider a full metal coolant reroute kit.

(Note: EGR deletes are for off-road/competition use only and violate EPA emissions regulations.)

Need a metal connection? Let me know—I’ll help you choose the right parts!

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