I have a 97 Grand Am and I am changing the main abs and master cylinder and there was no brake system leaks. I was wondering if I have to bleed the entire system or can I just bleed the abs unit or if so what would be the proper procedure of bleeding the system.
Your post does not make much sense. You are changing the ABS and the master cylinder? Why? I can see changing out the master cylinder if you have a pedal that is mushy, but you don't state that. Why change out the ABS? It seldom goes bad. Of course you will have to bleed the entire system if you change these out, as there's little hope you can change these two components without introducing air in the lines. If you haven't ever changed the fluid in your brakes, then by now it's most likely due to be changed anyway.
The ABS does have bleeders on it and you'll need to bleed it, but it's almost a guarantee that you'll also have to bleed each line. It can be a pain right in the butt to get all of the air out of an ABS system. Be prepared for a lot of bleeding.
The proper bleeding instructions would be in a GM factory shop manual which you can order from your dealer. This may require special bleeding tools to open combination valves and a Tech II scan tool which would be needed to "cycle" the ABS pump and solenoid valves while bleeding.
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