HOW A COOLANT RESERVOIR WORKS The coolant reservoir holds coolant from the engine cooling system. As coolant heats, it expands and pressure builds, sending excess fluid to the radiator. When the engine cools, the coolant is drawn back into the reservoir. If you have leaks, a low coolant level, or an overheating engine, the reservoir may be the source. COMPATIBLE WITH THESE VEHICLES - Mercedes-Benz C-Class W204: C180 (2011-2015, 2013-2015), C200 (2010-2014), C230 (2008-2009), C250 (2010-2011, 2012-2015), C280 (2008-2009), C300 (2008-2012, 2010-2014), C350 (2012-2016) - Mercedes-Benz E-Class W212: E200 (2012-2013, 2014-2016), E250 (2014-2016), E300 (2012-2016), E350 (2010-2016), E400 (2015-2017), E550 (2012-2017) - Mercedes-Benz CLS-Class: CLS350 W218 (2012-2014), CLS350 W218 (2012), etc. REFERENCE PART Replace For: EPT0029, FRT2412C, Z49042, 210501061564, 2045000049, 2045000549, 2045000749, 603-257. Package Included: 1 x Coolant Tank Reservoir without Cap, with sensor. Notice: instruction is not included. Recommended you install under the guidance of professionals. REPLACEMENT INSTRUCTION Turn off and cool down the car. Disconnect the drain line, remove the retaining bolts, and swap in the new reservoir tank.