im having problem with my brakes and its giving me a headache.

with the car off, applying pressure to the brake pedal, it would get hard. when i start the car the pedal goes down a bit. but after the car is started, the pedal would get soft with no pressure. i would need to press on the brake twice for it to stop.

car is a 92 dx with stock drums and 99si front brakes. i replaced the booster with a different one from a 93lx non abs and master cylinder is a 13/16.

lines for mc to prop valve are earls hyperfirm brake hoses including the fronts. the rear are oem hardlines.

bleed the system numerous time and bench bleed the master cylinder also.

 

So you already bled the lines and added brake fluid or checked for leaks?

 

yea added brake fluid and level is still the same

 

bumpin

 

BiZzumP

 

I had the same problem with my 95 SI. Tried all the things that you tried and some more. Since this condition can be caused by sticky pistons in the calipers, warped rotors, bent backing on the pads, and a lot more stuff... I finally replaced the front calipers, pads and rotors. Total cost around $155! ..... Solid pedal and ultra fast response. Hope your fix is this simple.

Then I upgraded from the SI 9.5" rotors to 93 Civic Ex Coupe 10.3" front hubs/rotors/calipers. Now, I have the opposite problem. After driving for about 5 miles, the front brakes start binding on the rotors without me ever touching the brake. If I let the car sit for 15 to 20 minutes, the binding clears and I'm ready for another 4-5 miles. I'll post when I resolve this issue.

BTW... It's normal for the pedal to get softer after the engine is started. The power brakes run off engine vacum and multiplies your pedal pressure by a substantial amount making the pedal easier to push. The power brake booster stores vacum so it will still work for a couple of brake applications after the engine stops running.

Hope some of this helps...

 

I had a similar prob with my b16 del Sol with the pads on both the fronts and backs. Even when I'm using new Honda pads in stock calipers.

I only know the discs (not drums - that's maybe a whole other problem)

Rust likes to build up in the groove that the pad tabs (ears) slide in, in the caliper body under the chrome spring things. When those grooves are rough and rusty the new pads get wedged in, and don't contact the rotor flat like it should.

If you had to whack or hammer the pads until they "snapped in" you'll see this problem.

When you're braking, you'll get like the top of the pad to touch the rotor, but the bottom's stuck and not touching the rotor. Probably the pedal sinking has to do with the different caliper squeeze force of manual braking vs. boosted braking (engine running).

Last time I pulled my pads out, took out the springy things and sanded all the rust out of the corners and flats and nooks and stuff. Touch up and grease the springs too. For the new pads, look at how the steel backing plate is stamped out by machine. If you lightly grind off the burrs from the cheap manufacturing of the pads, it should slide in your cleaned out groove much better.

With the pad able to slide in and out nice and straight, it made a big difference in my braking, and the pedal felt nice and solid.