Audi Engine Coolant Thermostat - Genuine Audi 0P2121115E

Product Information

Audi Thermostat diagram for A8, S8, SQ7, SQ8, RS6, RS7, RS Q8

Thermostats are a simple device which regulates coolant flow through the engine. When cold it will stay closed, stopping coolant flow and helping the engine warm up faster. Once up to temperature, it will open and allow normal coolant flow and maintain proper engine temperature. Always install with the 'jiggle pin' bleed valve at 12 o'clock when possible.

For many applications, multiple temperature ratings are available. These ratings denote when the thermostat opens, and in extreme climates different temperature ratings can be used to assist the vehicle in maintaining proper temperatures. In very hot desert climates for instance, a lower temperature rated thermostat may be preferred.

There are two types of thermostat failures:

Thermostat stuck open (most common): Coolant will flow through the engine constantly from cold, preventing the engine from reaching operating temperature. Usually this means a rich mixture resulting in poor fuel mileage and potential catalytic converter damage.

Thermostat stuck closed: If the thermostat is stuck closed it will restrict flow into the engine resulting in an overheating condition, resulting in potential catastrophic engine damage.

• Overheating engine
• Engine not reaching optimal running temperature
• Radiator fan not engaging

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.