I would try running more water and less antifreeze and adding Redline water wetter. instead of 50/50, try 75/25 in the summer. change back to 50/50 when it gets cold. It could also be your radiator is partially clogged and needs to get rodded out or replaced.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car