63 t bird sounds like its missing a little when its idleing and I just noticed that when I push the brake pedel it runs perfect. the car is stock with a performer rpm intake , holley, 2.5 inch duals with flowmasters. the booster and master cyl is only a few years old and I had to replace the master cyl already from rust in the master/ loss of brakes & fluid pressure. when I remove the vac***e hose from the booster and plug it it runs perfect. I removed the master cyl and started the car. the rod that goes from the booster to the master pushes out almost 2-3 inches when I hook up the vac***e line when the car is idleing...is it supposed to do that?.....it then retracts when I disconnect the vac hose again. I checked to see if the brake pedel was all the way up and tried it again and it did the same thing. Is my booster bad??? could the rod that goes from the pedel to the booster be out of adjustment some how?? ive had probloms in the past with this car dragging the brakes and I thought it was from the master going bad but hadnt loss pressure at the time, like the cyl was sticking but not leaking into the booster yet. it did leak into the booster, I wiped it out the best I could, would that ruin the booster?? Ive had this car along time and the brakes have always been a problem, any help would be greatly apreciated!!! thanks guys!!
yeah it does have a check valve in it i think, is that the place where the vac***e hose hooks up, its a plastic thing that acctually has two ports to hook up the vac hose, a small one and a large one, the large one is where I have the hose hooked up. the small one is capped. should i try to take it out and look at it? ive taken other ones out before and ive broken a few, thats why i havent messed with this one yet.
anyone with other Ideas? does it definately sound like the boosters bad?? thats a good chunk of change to be wrong, but Id give it a shot. its just hard to swallow cause I just replaced it a couple years ago. anyone know of a quality place where I could get a better quality booster. this one came fro MAC'S t bird parts (in ny?) thanks guys!
Based on your description, it's not the diaphragm in the booster that is bad, it is the valve within the booster that is leaking when there is no pressure on the brake pedal, and when you step on the brake the valve moves to a position that seals. Did you know you can take the booster apart? There's no black magic in them, really a pretty simple machine. Just a diaphragm and a "moving" valve.
I thought it was really weird that it ran better when I stepped on the brake pedal..... before I go buy a new one I will take this one apart and see if it looks like I can do something with it. maybe a bad o ring or something. any I deas on where to get parts for the booster if I need anything??........as far as going to mannual brakes...Im not totaly ruling it out but 4,400 pounds is a lot to stop....especially with the family inside....
have you tried hooking a vacuum gauge up to the motor.... if the gauge goes up when you push on the brake pedal that would probably indicated a leak somewhere in the booster....
If the brakes are "dragging", it sounds like the brake rod is too long. Is there an adjustment on the rod? Diaphragm sounds like it bad as well, could be a result of the rod being too long........
Make sure you buy a quality booster next time. The cheap chinese boosters are junk. that's why I switched to Hydroboost. I would double check the valve. You definitely have a vacuum leak though.
Test the valve. It should only work one way. Check the grommet on the valve, it may be deteriorated. Test the booster with a Mighty Vac. It should hold 20". Test your vacuum lines to verify they are not leaking.
A bad check valve wouldn't cause this problem. The check valve is used to keep a higher vacuum in the booster when the engine vacuum drops. That's why your power brakes will work a time or two with the engine shut off. You really need to determine if the booster issue is a leak when the pedal is not pressed, or if it is a leak when the pedal is pressed. Plug the booster line and start the engine. Is it running "good" like when you press the brake pedal, or is it running "not as good" like when you don't have the pedal pressed? This will set a benchmark as to what condition is occurring when you press the pedal. Can you hear a hiss that goes away when you press the pedal? Might have to get down under the dash to listen.
Replace the booster,as Ebbsspeed said does it make a hissing noise inside of car when you hit the brake pedal,if so when you mash the pedal you are sealing the leak,most places now sell the booster and mastercylinder as a unit.
unplug the hose to the booster and cover it up with your finger. If it idles better then its the booster. I would think that you would be able to tell that you have no ***ist from the booster when braking though? Can you not feel the difference in braking?
the car runs much better when I remove the vac***e hose and plug it. when I drove the car before I took it apart to work on this, the booster still seamed to work ok as far as the power asist. Im going to pull the booster off and check to see if their is an adjustment between the pedal ***embly and the booster...it sounds like the booster might not be returning all the way but that still dosent explane the rough Idle when the booster is hooked up. It sounds like somthing inside the booster could definatly bad right now, but I wonder if the adjustment behind the booster, if there is one , could be wrecking the boosters that I have put on over the years......this would be the third booster in less than.....definately, a thousand miles, but its been years in between.................man I need to drive this thing more.
the car runs much better when I remove the vac***e hose and plug it. when I drove the car before I took it apart to work on this, the booster still seamed to work ok as far as the power asist. Im going to pull the booster off and check to see if their is an adjustment between the pedal ***embly and the booster...it sounds like the booster might not be returning all the way but that still dosent explane the rough Idle when the booster is hooked up. It sounds like somthing inside the booster could definatly bad right now, but I wonder if the adjustment behind the booster, if there is one , could be wrecking the boosters that I have put on over the years......this would be the third booster in less than.....definately, a thousand miles, but its been years in between.................man I need to drive this thing more.
There should be an adjustment at the pedal. Check both adjustments at the pedal and between the master and booster at the push rod. You want about 1/8 or so of free play before depressing the push rod at the pedal. The fact that the pedal releases sounds like there is an adjustment issue, like maybe its adjusted too far out. When you unbolt the master from the booster there needs to be a small amount of space between the push rod and master. You shouldn't have to push the master onto the booster depressing the piston. You want just enough clearance to bolt the master to the booster without depressing the piston.
that sounds rite . the way it is now when I put the master cyl on the booster it pushes the rod coming out of the booster , into the booster. ..............Im pullining the booster off to check things out, be back with more info soon , thanks guys....
There should be just a very little bit of wiggle on the rod that goes from the brake pedal to inside the back of the booster, when the brake pedal is released. Crawl under that dash and figger it out! Good luck!
gonna try to get a pic of the car up so we can see what were workin on.... FE, rpm intake, 600 holley, truck manifolds, 2.5 inch duals , flowmasters, c-6 conversion, 2500 hughes converter, heavy clutches, bands, shiftkit, big cooler, soon to be 4.10 rear........part of the family for over 20 years......
you can put a little modeling clay on the end of the rod, then install the booster, bolt it up, and remove it, now look at the clay,if it's pushed all the way back to bare metal, the rod is too long, there should be just a small amount left on the end of the rod, you should actually be able to see the clearance in the impression, don't push the pedal during this test, you are checking static clearance
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