What part number is STI radiator cap?
There isn’t a single universal STI radiator cap part number. The exact number depends on your Subaru model, year, and engine, and STI often uses the same OEM cap as the base model. To identify the correct part, you’ll need vehicle specifics or the exact cap on hand.
Understanding the question
Radiator caps vary by application because they must match the cooling system’s pressure rating, thread size, and overall dimensions. When Subaru’s STI badge is involved, some buyers assume there is a distinct “STI” cap with a unique part number, but in many cases STI-released or STI-branded components reuse Subaru’s standard OEM parts. The result is that multiple part numbers could be correct depending on the year and model of your car.
Key considerations when locating the right part
To ensure you get the correct radiator cap, follow a precise identification process that accounts for model year, engine, and production changes. The steps below help you avoid ordering the wrong cap.
Before you begin a list of steps, note that the radiator cap is a small, often overlooked component, but selecting the wrong one can affect cooling system performance. Use the steps to verify the exact fit for your vehicle.
- Gather vehicle specifics: model (e.g., WRX STI, Outback, etc.), year, engine code, and VIN if possible. These details determine the appropriate cap and pressure rating.
- Inspect the current cap for markings: many caps show a part number, pressure rating, or manufacturer (often “Subaru” or “STI” branding) on the underside or side.
- Check official Subaru/STI parts catalogs: use the exact model year and engine to search for “Radiator Cap” or “Cap, Radiator.” Compare the listing with the cap you have (thread size, diameter, and pressure rating).
- Consult a dealership or STI-authorized service center: provide your VIN and they can pull the precise OEM part number from the Subaru parts system.
- If you cannot locate a number: obtain a replacement OEM Subaru radiator cap that matches the system’s pressure rating and cap diameter; verify fitment before installation.
These steps emphasize using official catalogs and your vehicle’s identifying details to avoid mismatches. An exact part number can vary across model generations, even within STI-branded lines.
What to expect in practice
In practice, STI-branded components are often aligned with Subaru’s own parts ecosystem. That means the radiator cap you need is usually a Subaru OEM cap made for a specific model and year, rather than a unique STI-only part. If you own a modern STI vehicle or a special edition with STI badging, expect the part number to be one of Subaru’s standard radiator cap part numbers that correspond to your exact model and engine code.
Common pathways to confirmation
To confidently confirm the correct part number, consider these reliable sources:
- Subaru official parts website or Subaru Parts Catalog app
- Authorized Subaru/Sti dealers or service centers
- VIN-based parts lookup tools provided by Subaru
- Owner’s manual or the underside of the existing radiator cap, if legible
If you share your exact model, year, and engine, I can help narrow down to the most likely part number or guide you to the precise catalog entry.
Additional context and practical tips
Radiator caps come in different pressure ratings and thread sizes. The cap must seal properly and maintain the correct pressure for the cooling system. Installing a cap with the wrong pressure rating or incorrect thread size can lead to coolant loss, overheating, or venting issues. When in doubt, replacing with the exact OEM part is the safest approach.
Summary
There is no single STI radiator cap part number applicable to all cars. The correct number depends on your Subaru’s model, year, and engine. To identify the precise part, use official Subaru/STI catalogs, verify with the vehicle’s VIN, inspect the current cap for markings, and consult a dealership or STI-certified technician. Providing your exact model and year will allow me to help locate the most likely part number and catalog entry.
