I'm just a shade tree mechanic. And this is just a guess. You say you have 4 lines running to the MC, one for each wheel. I'm assuming that means this MC has 4 independent ports. In that case, after you bleed one (or more) of the wheels, that last one can't be bled properly. The back pressure of the other independent ports are keeping the brake pedal from pumping pressure into that last line. In a case like that I would recommend one of those vacuum bleeding tools to remove all the air from the last line. I have never seen a MC with 4 independent ports. Pooh Bear

First you are correct about the fact that if you want to lock up the brakes you should be able to do that. The parking brake when you try it should be able to lock up the rear brakes and slide the wheels. So the question arrises, why can't you? First check. Pump the brake pedal about five times and hold it, memorizing how much pressure your placing on the pedal, and how far from the floor the pedal is. (You can use your other foot for a gage if you want to). Now release the brake pedal and wait about ten seconds. Step on the pedal a single time, using the pressure that you think you did when you held the pedal a few moments earlier, and see how high the pedal is from the floor. Is it exactly in the same place? Is the pedal lower? Memorize the pressure your applying, and the height of the pedal, and quickly pump it three times, and see if the pedal height changes. If the pedal ended up at the smae point each time, then your adjustment of the rear brakes is correct, and you don't have any air in the system. If the pedal height incresed when you pumped the brakes, then you could either have an adjustment situation, or still have air in the system. Next step. Apply brake with same pressure as before. Without releasing the pedal, start the engine. Vacuum from the engine should cause the booster to begin to assist you in applying the brakes, and you will feel the pedal fall from your foot. Maintain the same pedal pressure, and see how much further the pedal travels. It takes some experience to feel when this assist is sufficient, but at least you can tell if you indeed have assist or not. A bad booster, or vacuum problem will only give you about an inch or less of pedal travel increase. You will need to investigate the cause if you don't get a good assist. The next possibility requires an assistant. Put the car up on jacks and jackstands with all four wheels off the ground. Put the transmission in neutral. Pump the pedal three to five times to bleed off booster vacuum. Now have an assistant start to lightly press on the brake pedal while you turn the LF wheel by hand. Keep telling the assistant to increase pedal pressure slowly until you cannot turn the wheel with a moderate effort. have the assistant memorize the pedal travel at that point. Release the brake pedal, and repeat the process at the right front wheel. Now do it again for both of the rear wheels. The pair of front wheels should take the same pedal travel, and the rear wheels will each take slightly more than the front in most circumstances. All four should not need to have the pedal pushed more than half way before you cannot turn the wheel. Having made all of these checks, and not making any errors, you are now faced with the likelyhood that you have glazed linings, or at least linings with poor friction characteristics. All of the linings, the rotors, and drums may need replaced on a vehicle this old. Remember to include the hardware for the calipers, as well as the brake shoe hold down, and return springs (Maxipack). Make sure that if you replace the pads and shoes, use top of the line components, thats the only way your going to make sure you have something that should perform correctly. If all of this looks like a lot for doing something as "simple" as brakes, ""you aint seen nothing yet"". Lock-up charateristics, and point of lock-up are aspects that even as techs we normally do not have to concern ourselves with because normally the cars are engineered well enough that they almost always work. We only run into problems like that when we are dealing with improper materials, contaminated materials or the very rare, failed proportioning (or combination) valve. We actually have tools available that allow us to remove the bleeder screws, and directly measure the brake fluid pressure. Some shops have tools that fit in the caliper in place of the brake pads and rotors, in order to measure the systems ability to squeeze the pads and rotors. All in all it can be extremely complex especially when we have to deal with the opposite complaint of an early lock-up, or an antilock brake issue which essentially adds an entire system on top of everything else I have already mentioned here. I hope this helps. If there is any doubt, take it to a real pro to have this checked.

I have encountered this problem on many vehicles in the shop i work at and it might be normal for a brake pedal to travel quite a bit when your are at idle in park. However, you would never press the pedal that hard or as far down when driving. You would end up through the windshield for sure. In my experience your particular vehicle has this weird feeling pedal travel when you are idling in park but the brakes perform as they should when driving. Air in the hydraulic system would cause a spongy feeling not a fading pedal, so bleeding is not likely to fix the problem. if there is in fact a failure in the system I would be checking to see if the ABS module is bypassing fluid pressure by blocking off the master cyl. if the pedal is high and firm( no travel) I would then block off the flex hoses and check for pedal height and drop. if this is ok un-block one flex hose at a time and see how much drop if there is a substantial drop at a certain wheel I would verify the hydraulic circuit to that wheel. first by bleeding to see if there is any air. Then I would put my attention to the hydraulic unit. Though I am confident that this is how these vehicles are and you don't have anything to be concerned about. Hope it works out

. There NEEDS to be some residual pressure in the lines when the brakes are not applied . . . this keeps the seals tight against the bore; which prevents leakage. Even though the piston still moves; it does not mean that it moves freely enough . . . time will slowly accumulate gunk; and brake fluid by definition absorbs water from the air . . which can eventually accumulate and start rust / corrosion. If the line is plugged; you'd not get decent braking out of that wheel. Besides; pressure in a closed system is the same everywhere . . . I'd say it's new caliper time . . . Bob