Symptoms of a failed Mercedes thermostat
Once you confirm that your thermostat has failed, follow the instructions below to learn how to replace it. Replacing the thermostat is easy. Make sure that the engine is cold before you start replacing the thermostat on your Mercedes-Benz.
How to replace the thermostat
Tools you will need:
|FEMALE E-TORX (Star) SOCKET Set w/RAIL E4 – E20|
|3/8-Inch Drive Socket Set|
|Mercedes Engine Thermostat + Aluminium Housing + Seal Gasket|
|OES Genuine Coolant/Antifreeze 1 Gallon|
Step by step instructions
- Locate the thermostat. To replace the thermostat, you will need to drain some coolant from the radiator. At the bottom of the radiator of your Mercedes-Benz there should be a drain plug. Loosen it to release some coolant.If you decide to not remove the coolant note that there will be coolant spilling from the radiator hose and thermostat when you remove the thermostat from the housing.
- Loosen the radiator hose clamp.
- Use theE-Torx socket to remove the two thermostat bolts. Unplug the electrical connector from the sensor if your car has one. The sensor is typically found on 2008,2009,2010 and newer models such as C300 and E350. Remove the thermostat from the engine block. If the thermostat doesn’t come loose, you may need to pry it away using a flat screwdriver.
- Install the new thermostat in reverse order. Ensure that you have a new gasket for your thermostat. The old gasket should be removed and discarded.
- Tighten the two bolts and reconnect the radiator hose. Do not overtighten the two bolts. If you have a torque wrench, you can tighten these two bolts to approximately 10Nm.
- Add coolant to the radiator expansion tank. Make sure there is no air trapped in the cooling system.
- Start the engine. Ensure there are no coolant leaks near the thermostat.
Mercedes-Benz Thermostat Problems and FAQ
What are some symptoms of thermostat not working properly on my Mercedes-Benz?
Your Mercedes-Benz could overheat or take too long to reach operating temperature. When engine takes to long to reach operating temperature, the ECU will turn on the Check Engine Light / Warning Light.
Do I need a new thermostat if the check engine light turn on?
In Mercedes-Benz E, C, S, CL, CLK, SLK, GL, G, ML models, the engine control unit monitors how long it takes for the coolant to warm up. This is important for the engine. Only when the operating temperature is reached, do you get the best fuel efficiency and minimal wear on the engine.
At wat temperature does the thermostat open up on a Mercedes-Benz engine?
While this can vary, in the E320 and C240, for example, the thermostat opens up at 87-degree Celsius.
What happens if the thermostat fails in the open position?
If the thermostat fails in the open position, it prevents the coolant from reaching normal operating temperature resulting in an engine that does not warm up properly and an engine warning light illuminating.
Fault codes that can be triggered due to engine coolant thermostat failures.
P0128 – Coolant temperature below Thermostat Regulating temperature fault code.
Mercedes thermostat part numbers.Mercedes M112 M113 Thermostat + Aluminium Housing + Seal 1122030275 will fit the following Mercedes-Benz models:
2005-2005 E320 4Matic
2001-2006 CLK55 AMG
2001-2002 S55 AMG
2001-2002 CL55 AMG
2003-2004 G55 AMG
2000-2003 ML55 AMG
1998-2000 C43 AMG
1999-2002 E55 AMG
2005-2006 C55 AMG
2005-2005 E320 Base
2002-2004 SLK32 AMG
Mercedes-Benz C230 203.052 2006-2007
Mercedes-Benz C280 203.092 2006-2007
Mercedes-Benz C300 204.081 / 204.054 2008-2011
Mercedes-Benz C350 204.056 2006-2011
Mercedes-Benz CLK350 209.456 / 209.356 2006-2009
Mercedes-Benz E350 211.087 / 211.287 / 211.056 2006-2009 2010-2011 GAS
Mercedes-Benz GLK350 204.987 2010-2011
Mercedes-Benz ML350 163.157 / 164.186 / 164.156 / 164.125 2003-2009 2010-2011 GAS
Mercedes-Benz R350 251.165 2006-2009 2010-2011 GAS
Mercedes-Benz SLK280 171.454 2006-2008
Mercedes-Benz SLK300 171.454 2009-2011
Mercedes-Benz SLK350 171.456 / 171.458 2005-2012
Mercedes Thermostat Replacement Cost
|DIY Cost: Under $100 Auto Repair Shop: $200-$350|
|1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012|
|E 320, E 500, C 320, C 240, C 32, E 430, E 55, S 500, S 430, S 350, E 350, E 500, ML 320, ML 350 SLK 320 SLK32 AMG CL 430 CLK 320 350 500|
|Task Difficulty: Easy|
|Required Time: 30 Min|