Most who do that, buy the whole OEM assembly, rob the cap and diaphragm from the new and replace it on the old cover. They normally don't go to the hassle of removing the diaphragm from the cap and replace onto the old. If you do this, just make sure the spring inside is properly aligned or you'll be doing it again and again until correct.

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'01 740i Sport MKIV, Quad Brake Lights, Bi-Xenon retrofit, HID Fogs Dinan 7 Struts, Springs, camber plates, Intake, MAF, CAI, Throttle Body, NBT Retrofit, Strong Strut


'99 318ti Titanium Silver; '97 318ti Boston Green; '13 X5 3.5i Saphire Black Metallic
'84 633csi Black (sold); '88 325iC Black (sold); '97 740iL Black(sold); '01 740iS Black (sold);'97 318ti White (sold); '08 X5 4.8i Titanium Silver (sold); '96 318ti Alaska Blue (sold)