Audi Engine Coolant Reservoir Cap - Genuine Audi 4M0121321R

Product Information

The engine coolant reservoir cap is a critical component of a vehicle's cooling system. It seals the coolant reservoir or expansion tank, which holds excess engine coolant and maintains pressure in the cooling system. The cap is designed to release pressure at a specified level, ensuring that the cooling system operates effectively without excessive pressure buildup.

• Coolant Leaks: A damaged or improperly sealed cap can lead to coolant leaking from the reservoir, which may be visible under the vehicle or around the reservoir itself
• Overheating Engine: If the cap fails to maintain the proper pressure, it can cause the engine to overheat due to a drop in the boiling point of the coolant, leading to inadequate cooling
• Low Coolant Levels: Frequent need to add coolant to the reservoir may indicate a faulty cap that isn’t sealing properly, allowing coolant to escape

About Genuine Audi

The original parts used by Audi to build your car are available as replacement parts under the “Genuine Audi” brand. Manufactured under the direction of Audi, expect excellent quality and a premium price since these parts are available exclusively through the Audi Dealership network.

You may not realize this, but the parts that make up your Audi are not necessarily manufactured by Audi. No cause for concern, as Audi designs the part, hires a manufacturer, and ensures its quality to you. In fact, many of these manufacturers have been making parts for Audi for decades. In our industry these manufacturers are called OEM (Original Equipment Manufacturers), and these are often brands you recognize, including Lemforder, ZF, Sachs, Bosch, Valeo, Zimmermann, Siemens VDO, Corteco, and more. Don’t be surprised to open that Genuine Audi parts box and find an OEM branded part inside, simply with the addition of an Audi logo.

Be sure to keep an eye out for OE tags on our product pages to quickly identify parts coming direct from OE manufacturers. That extra bit of insight could save you some serious money while shopping! Refer to our OE Academy for further information regarding the OE/OEM tags throughout the site.