brake problem

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Aug 28, 2002
ok im trying to get my 40 working and stoping, iv had problems with the front brakes before so i rebuilt them and put on a new master cylinder. but i still cant get the brakes to work much at all. i have bleed them many times, i cant find the problem. when i press on the brakes i can still spin the tires w/ my feet. also every time i press on the brakes i hear an air leak, im assuming its my brakes booster, but would that effect how tight my brakes work?
im sure you did, but just to state the obvious, did you adjust the pads?
i believe as long as you dont have to pump your brakes your boosters ok. if your pumping think you have air in your lines or a bad booster.
I went through the same problem about a year ago when I first got my 40. Even after rebuilding the wheel cylinders and replacing the pads, The brakes were still giving me trouble. Turns out, instead of following the directions on re-installing the brake hardware, I put everything together like the PO had it ::) . Long story short and many close calls later, it turned out that the wheel cylinders on the front axle were on the wrong sides and upside down which kept me from bleeding the brakes propery. Also the little "ramps" on the adjusters were facing the wrong way (the part that contacts the shoe). LOL, I drove around like that til I started my brake system overhaul 2 weeks ago :eek: .
Booster. That air hiss is means any combo of 3 things-Vacuum leak at engine block, bad/loose tube to booster, bad booster. I thought I had a bad booster but when I replaced my intake/exhaust manifold gasket my booster quit hissing. Without the booster functioning properly you essentially have manual brakes=barely any braking power. Also could be wheel cylinders, it was that too on mine (I've had nearly every brake problem possible). But since you've just rebuilt yours that sounds fine. Also, if you press the brake at idle and you get an irregular or slower idle that is an indicator for one of the above three sources of hiss and weak brakes.
Make sure ALL of the shoes are adjusted right and make sure all of your hardware is installed properly, also make sure that everthing is bled correctly....BTW, did you bench bleed your Master cylinder before installing it? Even without a booster, you should be able to bring the vehicle to a stop (with considerable effort). Try puming the pedal but dont let the pedal come all the way back up to the top (It will uncover the compensation port) and If you fially get some resistance in the pedal after a few strokes, then you need to make some adjustments to the shoes. If It starts feeling sopngy and you get some resistance after a few strokes, then you still have air in the lines and you may still need to adjust your shoes. I cant remember the trouble shooting for the booster so I cant help you there but good luck on you repairs!
7/70 - 9/75 When pressing on the brake pedal a hissing sound, a rapid change in idle or a rough idle are signs of a brake booster malfunction. Bad boosters will burn the exhaust valves in #5 & #6 cylinders. To Check Your Booster: Engine Off - press the brake pedal several times, pedal travel should not change. Start engine, pedal should move down a little and the pedal pressure will get softer. Press the brake pedal all the way down, shut off the engine, the pedal should not change position. Restart the engine, run for a minute and shut off, press the pedal several times, the pedal pressure should get harder each time. If your booster does not work this way its time to rebuild or replace it. Before buying the repair kit please refer to the factory Chassis/Body manual for the repair procedure.  
BTW I'm convinced its either the booster is bad, or a vacuum leak at block. Thats the only part of the brake system that makes a hiss. Replace your intake/exhaust gasket with two stock ones from SOR and the hose from intake manifold to booster before you assume the booster is bad, I did those two things and now I no longer have a hiss.

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