How can i tell if my master cylinder and brake booster has gone bad? When i brake the pedal sinks the the floor.

All help would be apreciated ty.

 

try bleeding the brakes first, if that doesn't fix it, make sure your prop. valve isn't leaking, then if all that is good check for leaks in the vacuum lines from the booster, you might just replace the lines (and i think there is a plastic valve in the line too), then if all of that is fine and there are no leaks anywhere in any lines... i would do the booster and master cylinder together. Just pull one from a junkyard if you want to save money. I think i got one from a low mile 99 teg for about 20 bucks one time. Kind of a pain to get in and out but if its too difficult start with the MC first.