NHTSA complaint #11728476

Owner complaint summary

I have a MC Benz 300 GLC with $50,000 miles. I was having heating issues so took it to the dealership, which basically advised of the issue describer below, which would cost $14k to repair. Contaminated coolant in Mercedes-Benz GLC 300 models often results from the internal failure of a "desiccant bag" inside the coolant expansion tank, which disintegrates, releasing material that clogs the heater core. Symptoms include black residue in the tank, reduced cabin heat, and engine overheating. Key actions include replacing the expansion tank (reservoir) and flushing the entire system.