Where Is the Thermostat on a 2004 C230 Mercedes?


It was a brutally cold winter, and the biggest snow storm of the year was about to rear its ugly head. Sally -- a single mom who was always short on time -- went about her normal morning ritual of rushing out the door to a cold car, just to get little Billy to daycare on time. Normally this wasn't too big a deal, as her 2004 C230 always warmed up and had heat by the time she got to the first stop light, but that just wasn't the case today. Today, the car didn't have heat like it normally does, and the temperature gauge never even moved. Sally knew that once she dropped off Billy, she was on her way to see her favorite Mercedes mechanic, who would know exactly what to do.

Preping for the Job

  • Once Sally left the repair shop, Bob the mechanic got right to work. He found the coolant pressure cap on the passenger side of the engine by, right by the strut tower. Once he got the vehicle lifted, he removed the six 8 mm bolts that hold the cover to the bottom side of the engine carriage. With the cover out of the way, he was able to attach a 1/2-inch tube to the radiator drain cock. He turned the drain cock valve with a flat-head screwdriver. When the coolant had drained, he removed the hose, and replaced the cover.

Removing the Thermostat

  • To get to the thermostat housing, Bob removed the front engine cover by lifting up on both front corners. He used a flat-head screwdriver to pry the metal retainer for the coolant line up by about 1/2 inch, then he removed the hose from the thermostat housing. Because of the design, the thermostat housing on this particular vehicle is hard to remove, so Bob used a screwdriver to lightly pry it away from the engine.

Finishing Up

  • Bob was ready to install the new thermostat, but he almost forgot one important thing -- he had to replace the O-ring on the thermostat housing, and coat it with fresh engine oil. He did that, then tightened the housing bolts to 80 inch-pounds. Once the upper radiator hose was installed, he simply pushed the metal retainer into place. He press-fitted the front engine cover, then filled the engine with fresh premixed 50-50 G-05 engine coolant by adding it through the coolant reservoir. After running the engine up to operating temperature, Bob topped off the coolant and installed the reservoir cap. Sally's car was ready to be picked up by lunch time.

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