I have a 94 civic si, in the last 2 months, I have replaced both rear wheel cylinders, the master cylinder, and front brake pads. The rotors, shoes and drums are in excellent shape. My problem is that I still have a soft brake pedal even after I bled the system 5 times. I bench bled the master cylinder again, and that still didn't fix the problem. The brakes still stop the car just fine, but it should have a really tight pedal and I don't know why its not. Any ideas? The fluid is very clean and fresh, and I'm not leaking any wheres. The front calipers are in perfect shape, and I adjusted the back not that long ago.

Very unusual. Did you bleed brakes in this order: RR, LF, LR, RF? Did you use a one-man bleeder with a check valve in it, to prevent air getting into the system? If not, what did you use to bleed the brakes?

I used a piece of clear rubber hose and a small bottle with brake fluid in the bottom if it, and I had a friend pumping the brakes for me. I did it in the order you mentioned. I got my helper to pump them a couple of times and hold, and then I opened the screw a little bit and watched the fluid going through for bubbles. Since this is like my 5th time bleeding them, there is only fluid no bubbles. But it doesn't firm up the pedal

Your approach can wear the bleeder screws, over time. I recommend the fool-proof Brake Bleeder Economy One-Man, Cal-Van Tools, No. 247, brake bleeder for bleeding the brakes and hydraulic clutch. It costs $2.99 and has a one-way check valve. Here's a similar, more widely available, product from Harbor Freight:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98864

Did you tighten all fittings with a metric flare wrench?

I used a 10 mil wrench to tighten the fittings. I have about 1 1/2 inches of slack before my pedal starts getting firm. Could this be because of the aftermarket master cylinder and I need to adjust the pedal to remove the slack? I've bled my brakes in the past, and I had a really tight pedal. With all the new parts installed in theory I should have an even tighter pedal.

Before installing the master cylinder, did you check and adjust the pushrod clearance?

Not to be difficult, but you really should tighten all brake line fittings with a 10 mm flare nut wrench. Master cylinder-to-brake line fittings should be tightened 14 lb.-ft. Rear brake line-to-brake hose fittings should be tightened 11 lb.-ft.

With the engine off, depress the brake pedal several times, then depress the pedal hard and hold that pressure for 15 seconds. If the pedal sinks, the master cylinder, brake line, or a brake caliper is faulty. Most problems, in this case, involve master cylinder bleeding and/or adjustment. Finally, don't forget to check the pedal height adjustment.

I didn't check the piston to pedal clearance, ill take a look at that soon. I really need some flare nut wrenches. You've been so helpful man