ACDelco radiator cap RC85 15 PSI GM Original Equipment direct-fit replacement — spring-loaded seal

ACDelco RC85 (15042975) 15 P.S.I. radiator cap is a GM Original Equipment replacement that seals the cooling system and maintains the specified 15 PSI pressure for reliable engine cooling performance.

This ACDelco GM Original Equipment radiator cap is a direct-fit replacement engineered to the same specifications used by General Motors. It’s a spring-loaded pressure cap designed to seal the radiator filler neck or surge tank, preserve system pressure while the engine warms up, and return excess coolant from the expansion tank when the engine cools. Manufactured for durability and consistent performance, the RC85 (15042975) helps preserve the cooling system’s operating conditions and supports the long-term health of your GM vehicle’s engine cooling components.

How does the RC85 cap control cooling system pressure?

The RC85 uses a calibrated spring and sealing assembly to hold the cooling system at 15 PSI during operation. By maintaining the designed pressure, it raises the coolant’s boiling point within safe limits and helps prevent localized boiling or vapor lock under normal engine loads.

• Pre-set 15 P.S.I. valve for consistent pressure control
• Spring-loaded design that opens to bleed excess pressure
• Sealing gasket prevents coolant leakage at the filler neck

Will this radiator cap fit my GM vehicle?

The RC85 (15042975) is produced as a vehicle-specific OE replacement for many GM models. Check your vehicle’s service manual or parts lookup to confirm compatibility with your year and engine configuration.

• OEM part number: 15042975 (RC85) for direct identification
• Vehicle-specific fit type—match to your GM model for correct fitment
• Designed to align with original filler neck dimensions and sealing surfaces

What benefits does an OE ACDelco cap deliver compared with generic caps?

ACDelco GM Original Equipment caps are manufactured to the same tolerances and materials specified by GM, which helps ensure consistent pressure performance, proper sealing, and longevity. Using an OE cap reduces the risk of under- or over-pressurization that can shorten cooling-system component life.

• Built to GM quality and dimensional specifications for reliable fit
• Materials selected for durability under engine heat cycles
• Minimizes risk of coolant loss or pressure-related cooling issues

How do I inspect and replace the radiator cap safely?

Only remove the cap when the engine and cooling system are cool to avoid scalding from pressurized hot coolant. Inspect the cap for worn gaskets, weakened spring action, or visible corrosion, and replace with the RC85 if you spot any defects or if the cap fails to hold pressure.

• Allow engine to cool fully before removing the cap
• Check gasket integrity, spring tension, and exterior corrosion
• Install the RC85 by seating and turning until secure—verify a snug seal

Who is this for: The ACDelco RC85 (15042975) 15 P.S.I. radiator cap is intended for owners and technicians of GM vehicles seeking a direct OEM-style replacement. It’s appropriate for anyone who wants a factory-spec, vehicle-specific cap that preserves coolant pressure, prevents leaks at the filler neck, and supports the cooling system’s designed operating conditions. Ideal for routine maintenance, cooling-system overhauls, or whenever a damaged, leaking, or mismatched cap needs replacement to restore reliable cooling performance.