problem with 91 mustang brakes

[dauntless]

hello there, i have a 91 mustang gt and my brake booster (original) was not working and it was sucking vacuum inside the vehicle, i purchased a new one along with a new master cilinder, new brake lines ,new brake pads and new rotors, reason for purchasing the other components was because i figured i could refresh all these components while i changed the booster, once i was done and everything was bled properly i developed a problem, the car will stop but with some effort, i have had many opinions and they all center on a bad booster, when i turn the car on and hold the brake pedal i can feel it go down some which ive heard this means the booster is working, i also had a mechanic tell me that boosters can sometimes "halfway work" aftet checking everything including pushrod lenght and double checking everything i am leaning towards a bad booster also, it will not be the first time i have bought a part several times until i get one that works properly,basically i have a hard pedal and thats my problem, i would very much aprecciate any input from all the great members out there, thank you

[speedindevil]

have you tried hooking up a vacuum pump to the booster line and seen if it holds?
just a thought.

[dauntless]

Originally Posted by speedindevil

have you tried hooking up a vacuum pump to the booster line and seen if it holds?
just a thought.

hey thank you so much for your reply, no i havent tried that, at one point i slid the master cilinder back just far enought to adjust the rod and i pulled the rod out some by accident and i heard a swooosh (air releasing) so that told me the booster was holding air, a friend had another idea somewhat radical , he thinks the booster diaphragm is reversed, basically its working against me instead of with me,another idea i have is under the master cilinder there is a distribution block which contains the proportioning valve but also it does have other valves in it, maybe its blocked somewhere? if the pedal is pressed hard enough plenty of fluid comes out of the bledding screws on the calipers so fluid getting ther is not a problem, i think i will eventually get another brake booster, i bought it at oreillys(ive had issues before there) tell me what you think? thanks again

[speedindevil]

i'm not sure what the inside of the booster looks like, but if you heard that woosh, then it should be holding the vacuum ok. i had a problem like this on an 81 pickup, though, the brakes were real hard, and we had just bought it, so were driving it home and on the way home, one of the lines blew out. i'm wondering if maybe one of your lines got kinked, or if there's some rust or other foreign smegma in your lines, I know you just put them on, but how fast does the fluid come out when you bleed them? also, I don't mean to ask a stupid question, but are the lines hooked up the same way they were? I'm not sure that it would matter, but if they were flipped on the proportioning valve it might, other than just flipping the front/rear force.
I'd say if the fluid comes out quick and the pedal drops quick when you crack the bleeders, it's probably the booster.

[Davescort97]

Do a test on the check valve inside the brake booster vacuum hose. Disconnect the hose from the booster and the engine. Try to blow air through it both directions. Air should only flow toward the engine side of the hose. If air flows both ways or neither way replace the hose and check valve. Did you bleed the master cylinder by cracking the lines as well as bleeding the calipers. Just a few thoughts. You're probably right about the booster being bad from the package.

[dauntless]

hey there, thank you for your input again, you have covered pretty much everything, on the new lines i put in i could see how one could be on backwards and the valve could be working the wrong way but they can only go one way cause one has a bigger fitting than the other so they each go in a respective hole, this weekend im just gonna bite the bullet and change the booster, once i do that at least ill have the peace of mind that i checked and replaced it and that wasnt it, something else that ive noticed is that most cars including my tbird have a peculiar noise when the brakes are pumped, like when a ballon is being inflated and that noise is not present whatsoever in the booster i put in my mustang, theres no sound period, also in regards to your question, fluid does come very strong from the bleeder screws and the pedal does go down when the screws are open, i will pick up a new booster this weekend and install it and i will for sure let you know how the saga is going and most of all i thank you for all your input