Mercedes-Benz Engine Coolant Thermostat - Wahler 410389103D

Product Information

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 Wahler

Wahler is the leading OEM manufacturer of thermal solutions for BMW, Mercedes-Benz, Audi, Porsche ,VW as well as Volvo, Saab, Jaguar, Land-Range Rover as well as various US domestic and Asian applications.

Since 1902, Wahler has built its reputation with technically complex thermostats and thermos-solutions for automotive and industrial applications. For a short time, Borg Warner managed Wahler products. In 2020, Borg Warner sold all of the thermostat production facilities back to Wahler. Today, Wahler is back as an independent brand supplying worldwide OEMs with thermostats, electronic thermostats, thermoswitches and electric valves.

With Wahler, the original and replacement parts are identical. This means that Wahler-made parts are the same quality as the original issue used by automakers. The Wahler brand stands for premium quality. Wahler aftermarket parts come with the same assurances with respect to service life and operational reliability.