BMW Thermostat Assembly for M57N & M57N2 - MAHLE 11517805811

Engine Coolant Thermostat

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.

Engine Coolant Thermostat Failure Symptoms

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

About Mahle

Mahle began in 1920 when pistons made of heavy gray cast iron were being used in internal combustion engines for automobiles and there was a need for a new design. The Mahle brothers countered this trend by producing light-alloy pistons at their small, newly established company however the technology was still finicky and problems come up frequently. They soon determined that they needed to come up with a solution to keep dirt and dust out of the engine so they eventually developed air and oil filters as well. Their perseverance paid off and the light-alloy pistons began to take over the market. Today, half of all automobiles produced worldwide contain MAHLE components. MAHLE offers an extensive range of parts for everyone including pistons, cylinder liners, piston ring sets, bearings, assemblies, valves, valve train components, and air, oil, fuel, and cabin air filters. Their catalog and online database of aftermarket engine components is an indispensable reference.

OE
This is the original part used by the vehicle manufacturer when it left the factory - in other words, a Genuine product without the logo on it and without the premium cost. We recommend OE replacement as best options for quality and price. Vehicle manufacturers (BMW, Volvo, etc.) do not manufacture many products themselves, rather they contract their Original Equipment Manufacturers to do so. The products that we list as OE are guaranteed to be the exact same part that was on your car when it left the assembly line. In some cases they are even better quality than what is currently available in Genuine because over time some Genuine contracts get changed to save money. All of these parts will be stamped with the OEM’s brand name such as Bosch, Hella, or Lemforder but due to contractual agreements the vehicle manufacturer’s logo cannot be on the product and may be removed from the part.