A thermostat is a simple device that regulates coolant flow through the engine. When cold, it will stay closed, stopping coolant flow to help the engine come up to temperature faster. Once up to temperature, it will open and allow coolant to flow normally and maintain proper engine temperature. The thermostat has a finite lifespan and requires regular replacement throughout the lifetime of the vehicle.
Mercedes-Benz M156 Thermostat Replacement Symptoms
Thermostats fail in one of two ways, either stuck open, or stuck closed. When the thermostat is stuck open, coolant will flow through the engine constantly preventing the engine from reaching operating temperature. This will also cause the engine to run rich which will hinder performance and also potentially destroy the catalytic converters.
When the thermostat is stuck closed, it will cause the coolant to not flow into the engine resulting in an overheating condition. An engine that overheats runs danger of warping the cylinder head as well as blowing a head gasket, resulting in an expensive repair.
Symptoms of a failing thermostat on your Mercedes-AMG M156 range from minor annoyances to critical issues. The most prevalent of these symptoms are:
- Engine fan constantly running on high
- Coolant temperature dashboard error message
- Vehicle taking longer than usual to get to operating temperature
- "Open circuit" fault code for the MAP-controlled thermostat
Since the thermostat requires regular replacement, you should just be replacing it before symptoms ever arise to save yourself an immeasurable amount of headache. Replacement is required around every 50,000 miles.
Mercedes-Benz Models Applicable
This thermostat kit fits a wide range of Mercedes-AMG models that come with the M156 engine, including:
- 2007-2009 Mercedes-Benz CLK63 AMG
- 2008-2010 Mercedes-Benz S63 AMG
- 2007-2011 Mercedes-Benz CLS63 AMG
- 2008-2015 Mercedes-Benz C63 AMG
- 2007-2011 Mercedes-Benz E63 AMG
- 2009-2012 Mercedes-Benz SL63 AMG
- 2007-2011 Mercedes-Benz ML63 AMG
- 2011-2015 Mercedes-Benz SLS AMG
- 2007 Mercedes-Benz R63 AMG
- 2008-2010 Mercedes-Benz CL63 AMG
Parts Included with Mercedes-Benz M156 Thermostat Kit
In the video below, Kyle Bascombe, our Mercedes Whisperer/Catalog Manager gets up close with this Mercedes-AMG M156 Thermostat kit. If you're unsure if this kit will work on your car, you can verify the fitment by going to our homepage and use the vehicle selection tool in the upper left corner. As usual, if you like this Really Quick Product Review, subscribe and check back here for regular releases in the future.
Writer/Editor at FCP Euro and owner of a daily R53 MINI Cooper, a track-built R53 MINI, and a 1997 Dakar Yellow E36 M3 Sedan. ••• Instagram: @evan.madore