ok so my 1989 lxi has new rotos and pads on front rear shoes looked ok. so i got done with brakes and still had brake peadl travel going to floor board with pressure applied. bled brakes from passenger rear and all the way around still same issue do i need a new master cylinder? dont know much about brake booster but its states it has on in haynes please help!!! Thank you
that sounds like a bad master cylinder, if you replace it you need to possibly save the reservoir as some of them don't come with one, when you remove it the screen inside it lifts out so it can be cleaned and the entire reservoir can be cleaned,use regular brake cleaner to spray it and then wipe it out. make sure you bench bleed the new master as per the instructions with it, this has to be done first off the car, it's very important, bleed the brakes diagonally, left rear right front etc then the opposite on the other side
I agree that it's probably a bad master cylinder. I had the same brake pedal fade problem with my '91 Accord. Replacing the master cylinder solved the problem.
The brake booster is the unit that provides the "power" in power brakes. It is operated by engine vacum and not likely to be the issue. Especially if your pedal sinks even when the engine is off and there is no assist. If you didn't change/adjust the rear shoes, I suspect either you still have an air bubble or a bad master cyl. NOTE - on old cars, when bleeding using pedal pumping, put a brick or block under the pedal to limit its travel to it's "normal" range of motion. Otherwise, trash accumulated in the master cyl over the years can damage the master cyl's piston seals while you are bleeding the system and cause failure.
Found that one the hard way
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