for #3 i would say if you dont pay attention and put a 20psi cap on there you will find a weak link the system is supposed to operate at 14psi almost every single replacement cap i have found has been a 20-25psi not 14 like the car needs, I was having coolant leaks due to to high of pressure... now i have a 13psi cap and it appears all of my leaks may be gone, still watching... i also have lower temps as well not having leaks...

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85 mercedes 300D-T 258k miles