I bled the brakes on my car and adjusted them and everything, and i notice that when I step on the brake, the pedal is high at first, and then slowly goes down until I guess only the disc brakes are working. I'm thinking its either the booster or the rear wheel cylinders. Any clue?

Need more details bro....What year, is it a disc conversion? Right now it sounds like a bad master;)

its a 76. I got the car in March and it appears the rear brakes had stopped working. I never checked because the guy I bought it from said they were new. Shouldn't have listened. THey didn't work from day1 but it brakes great on just the discs. I had to remove a few of the cylinders because they were locked but I got them loose and it seemed everything worked. If it means anything, I hear a "woosh" sound when the pedal is going down, as if there is pressure for a few seconds, but then releases right away. Would there be any visible signs of a master cylinder being bad? I've checked for fluid leaks and there arent any. Also, when I had only my fronts working, the pedal never lowered afterwards. It was always constant.

its your master cylinder or your booster....the "wooosh" sounds like a vacuum leak in the booster...

-Max

I was thinking its the booster. I'm gonna pull the rear wheels off next week and check for fluid leaks. Just to see if its the cylinders.

it will be the master cylinder by-passing. If the booster is no good the pedal will be hard to push.
If the rear wheel cylinders are leaking the fluid in the resevoir would be low.

The reason I was wondering if it had a disc conversion is that I just solved a brake problem that sounded like that. Turns out the P/O tried to keep ucing the drum master after installing discs up front. After installing a 76 and up master thats made for front discs, my pedal stays up and there's no more by-passing going on ;)

look on the inside of your tire, if one of your slave cylinder has been leaking the fluid will be very visible on the tire. if i remember correctly each wheel has two cylinders.

I love the Pirate Bulletin Board....you guys are awesome!

sounds like an internal master cylinder leak. (You can use a drum brake master with discs(dual circuit) with out problems as long as you remove the reisidual pressure valve.) Bore diameters may be different(changing pedal effort) but they function the same. I would replace the master, but make SURE your rear wheel cylinders are all leak free and not frozen, as a partly frozen wheel cylinder can take more time to extend then a new one.

The woosh noise is not necessarily a bad brake booster. When the brake pedal is depressed the vacuum is alowed to enter the front part of the booster by the hose to the intake manifold. When that happens the diaphragm is pulled forward, assisting the pedal effort. The back of the booster is open to atmosheric pressure, and if you look at the pedal pushrod inlet you will see where air can enter to make up for thevolume change caused by the diaphragm moving. To check for a leaking booster, just leave it connected to the intake manifold and take a pair of vice grips and clamp the hose off and see if the idle changes... Depress the pedal and check again(pedal will be hard)

If you go to rear discs you can use the same master as before, just take out the stock proportioning valve and add a Summit performance one for about $40(you will need the metric to SAE thread adapters)... Tune the rear brakes to exactly what you like for bias.

Ok, I took off the hose and sealed it. The idle is the same as when its connected to the booster and when I press the pedal, its stiffer and still goes down, but much slower. I'm guessing because its not power assisted.