ACDelco GM Original Equipment RC85 (15042975) 15 P.S.I.

ACDelco RC85 (15042975) is a GM original equipment 15 PSI radiator cap engineered to seal the coolant system and maintain correct operating pressure for compatible GM vehicles.

When a cooling system doesn't hold pressure, engine temperatures and coolant boiling point can change, which may reduce system performance and increase risk of overheating. The ACDelco GM Original Equipment RC85 radiator cap is a direct-fit replacement designed to restore the original factory sealing, pressure relief and coolant recovery function found on many GM models. Built to OEM tolerances, this spring-loaded cap helps the cooling system operate as intended by controlling pressure and enabling coolant return from the expansion tank as the engine cools.

How does this radiator cap maintain proper cooling system pressure?

The RC85 uses a calibrated pressure spring and valve assembly to hold a 15 PSI threshold. While the engine warms, trapped air and expanding coolant increase pressure until the cap’s valve opens at the set rating, protecting hoses and radiator components from overpressure. As the engine cools, vacuum relief lets coolant return from the overflow reservoir to prevent air pockets.

• 15 PSI spring-actuated pressure valve designed to match GM specifications
• Vacuum relief to allow coolant return and prevent tank collapse
• Precision sealing surface to minimize leaks and maintain system integrity

Will the RC85 fit my GM vehicle and replace the original radiator cap?

This ACDelco cap is an Original Equipment (OE) part manufactured to replace the factory component on compatible GM vehicles. It follows GM fitment guidelines and is intended as a direct replacement where RC85 or part number 15042975 is specified. Always confirm compatibility with your vehicle’s year, make and model before purchasing.

• OE part number 15042975 / RC85 for direct, vehicle-specific fit
• Designed to match factory sealing geometry and neck dimensions
• Recommended by GM as a replacement for the original cap

What are the practical benefits of using an OEM ACDelco radiator cap?

Choosing the ACDelco GM Original Equipment cap helps preserve the cooling system’s designed thermal performance by maintaining boiling point and minimizing air intrusion. Proper pressure control reduces strain on hoses, gaskets and the radiator, supporting longer component life and more consistent engine temperatures under everyday driving conditions.

• Maintains coolant boiling point for consistent thermal control
• Prevents air pockets that can cause hot spots or reduced heater performance
• Helps avoid premature wear on cooling system parts through correct pressure management

How do I inspect and install the RC85 radiator cap safely?

Always allow the engine to cool before removing the radiator cap. Inspect the cap’s seal, spring and valve for wear, corrosion or debris and replace if damaged. Installation requires a firm, even press and twist until the cap seats and locks, ensuring the pressure and vacuum functions operate correctly.

• Only remove when the engine and coolant are cool to the touch
• Check the rubber seal and spring for cracks, rust or compression loss
• Seat and twist firmly until the cap locks; verify no leaks at operating temperature

Who is this for: The ACDelco RC85 (15042975) 15 PSI radiator cap is aimed at owners and technicians maintaining GM cars, trucks and SUVs that require a factory-style replacement cap. It’s well suited for anyone restoring correct cooling system pressure and coolant recovery behavior on compatible GM models, and for service shops seeking an OE-grade component for reliable fit and performance.