While driving my vehicle on March 3, 2025 the check engine light came on. Additionally my vehicle began to shake. I was scheduled for a service appointment on March 5, 2025 and told the service department the check engine light need to be addressed. Upon inspection, it was determine the cylinder head needed to be replaced due to a leaking exhaust valve. Estimated cost of $8,818.12. I was devastated and disappointed we had a 2020 Mercedes GLC 300 had the EXACT SAME PROBLEM in 2023. The cost to repair was estimated at $9000!!! How coincidental is that 2 vehicles in the same family have the same problem on newer model vehicles!!!! After researching the web, we discovered that the warranty was extended on the M260 cylinder head however my engine is M264 engine just for RWD cars. Mercedes will not cover it even though this is the 2nd GLC 300 that WE have reported the problem with the cylinder head. They would not even replace the part and we pay for the labor. I am truly disappointed and most likely never be a Mercedes purchaser again. Especially since they cannot stand behind their product. The cylinder head failed and caused my daughter to be placed in harm’s way by beginning shaking while driving. This could have caused an accident and put others at risk. This problem has been confirmed by 3 different dealerships on 2 different vehicles( 2020 and 2021 Mercedes GLC 300). It has been inspected by the dealership that confirms it is leaking and needs to be replaced and confirmd it was not the negligence of the driver. There were no warning signs besides the check engine light coming on.