ACDelco radiator fill cap RC27 (10409635) — GM direct-fit replacement, calibrated spring seal

The ACDelco GM Original Equipment RC27 (10409635) Radiator Fill Cap is a direct-fit replacement that seals and pressurizes your vehicle’s cooling system to help maintain proper operating temperature.

When a radiator cap wears out or fails, the cooling system can lose pressure, boil over, or allow coolant to escape — symptoms that can shorten engine life and leave you stranded. The RC27 (10409635) cap from ACDelco is built as a professional-grade aftermarket replacement designed to match the original equipment specifications for many GM vehicles. It restores the intended seal and pressure control so the radiator and coolant can do their job reliably.

How does this cap restore cooling system pressure and performance?

The RC27 cap uses factory-style sealing surfaces and a calibrated spring to maintain the designed pressure in the cooling system. By holding the correct pressure, it raises the coolant boiling point and helps prevent localized overheating or coolant loss.

• Calibrated spring ensures correct pressure release point
• Precision sealing face reduces leak paths and coolant evaporation
• Durable materials resist corrosion and repeated cycles

Will it fit my GM vehicle and match OEM standards?

This ACDelco cap is manufactured as a vehicle-specific, direct-fit replacement for many General Motors models. It follows the original equipment dimensions and fitment tolerances so installation is typically straightforward without modification.

• Vehicle-specific design for improved compatibility
• Meets fit, form, and function expectations of original parts
• Easy swap using standard hand tools—no system overhaul required

What materials and build features make it dependable?

ACDelco constructs the RC27 cap from quality metals and elastomers chosen for heat and coolant resistance. The assembly is engineered to maintain sealing force and spring performance over many thermal cycles, giving long-term reliability under normal driving conditions.

• Heat-resistant elastomeric sealing ring to prevent leaks
• Corrosion-resistant metal components for extended life
• Factory-calibrated spring for consistent pressure control

How simple is installation and maintenance?

Replacing a radiator fill cap is generally a quick, low-skill job you can do at home. Always allow the engine to cool fully before removing the old cap to avoid burns; then press and twist the new cap into place until secure.

• Cool engine completely before opening the system
• Press down and rotate to lock in standard cap-style bodies
• Inspect the neck and coolant level when replacing the cap

Who is this for: The ACDelco RC27 (10409635) radiator fill cap is intended for owners and technicians maintaining GM vehicles who want an OEM-compatible, professionally built replacement. It’s suitable for routine maintenance, cooling-system repairs, or anyone replacing a worn or leaking cap to restore correct pressure control and reduce the risk of overheating. Choose this cap when you need a vehicle-specific, dependable sealing solution that aligns with original equipment standards.