how to replace rear master cylinder on 1992 Buick Century

we are tryiong to put new brake cylinder on the rear

Asked by for the 1992 Buick Century
If you haven't done it before I suggest to get a repair manual and follow the steps exactly. If you are not 100% confident that you can do it - since it's an extremely important safety feature - leave it for a pro.
You can find great repair manuals with step-by-step instructions, diagrams, parts locations and other important information here:
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