03 si brake pedal goes from firm to really low in two pumps.

[apexracing]

Hello like the tittle says my brake pedal goes from firm to very low and soft within two - three pumps. after cruising the pedal gets hard again on its own then gets low and soft again. I started out replacing the front calipers. Then bleeding the brakes via two man job(not knowing this can damage my mc potentially) pedal felt ok at best after. Any ways i was cleaning up my engine bay and removed the brake booster vacuum line, when reassembling i accidentally hooked it up backwards and tried to drive away, pedal was rock hard. switched it back and the pedal was low and soft. over time it has gotten hard on its own when cruising and at idle then depletes and goes to soft within two-three pedal pumps. I installed stainless brake lines and re-bled(using the two man method again.) and still the same. So yesterday i replaced the booster and installed new hawk ceramic pads. didn't disconnect the brake lines from the master so i didn't have to bleed. but now my pedal still goes from firm to low and soft and now the brakes are really touchy and the front dives with a slight press of the pedal. so i'm going to try gravity bleeding it later, along with a rear caliper ebrake reset. but i am at my wits end. please any and all help will be appreciated even in the form of condescending insults lol. thanks guys.

[apexracing]

update did the ebrake pin reset buy loosening the e-brake cable and driving around. also stomped on the brake a few times to get the abs going. pedal felt great but then after pulling into the garage it started to get soft and low again, so i backed out and stomped on the pedal a few times and pulled it in. going to gravity bleed in a hour or so. looks like a good bleed with the air out of the abs might do the trick. but the way the pedal felt on my earlier test run leads me to believe there isn't any thing serious wrong.

[andyman97]

It sounds like it just needs to be more thoroughly bled. Hope that does the trick.

[apexracing]

It sounds like it just needs to be more thoroughly bled. Hope that does the trick.

yea i'm thinking so, my girl is on her way home with a brake bleeder kit so i can gravity bleed them. hope it works.

[andyman97]

Run a vacuum line from the bleeder valve and submerge the other end in brake fluid. You shouldn't need special tools.

[apexracing]

Run a vacuum line from the bleeder valve and submerge the other end in brake fluid. You shouldn't need special tools.

thats just what i did but i had her get a clear bleeder hose. i gravity bled each wheel with the motor off in order for about 30 min each. ended up using a coke bottle worth of fluid through the system. it was fine at first. but after driving a bit and letting the abs kick in a few times i drove a stretch just crusing then stopped to turn back onto my road and my pedal was soft and low again. i think i'm going nuts and could use further assistance from you guys.

[beechstreet]

bad master cylinder

[27rocks]

bad master cylinder

I'm going to take a guess its this ^^^.
There's not much to the system and by the sound of it you pretty much replaced everything but the MC. I would also check to see if all your hard line connections are leak free.

[apexracing]

Yea i'm not loosing any brake fluid. and all of my connections are leak free. when i changed and painted my calipers they were left off over night so quite a bit of fluid drained out but for christs sake i've bled the car 6 separate times. there was no fluid between the master and the booster so my guess is that its going internally. and when the pedal goes low and soft now the front dives pretty good. still sound like a master or do i just have stubborn air in there some where?

Edit after changing my front calipers i cant remember quite what the pedal felt like. but after i accidentally switched the booster vacuum line around is when this has started going down hill. i've replaced the booster, but what are my chances that the reversed vacuum line killed the booster and the master internally?

[RHCP0801]

when you bleed the brakes and its a steady stream of fluid, its not air in the lines. Sounds like you need a new master

[apexracing]

when you bleed the brakes and its a steady stream of fluid, its not air in the lines. Sounds like you need a new master

yup and i think i agree but can you verify my hypothesis that i edited into my previous post.

[apexracing]

well having read that the em2 ex civic has a better made master, is this statement true? i was considering getting a reman ep3 one by fenco from autozone as i can have it here in 2 days and it comes with the bleeder kit. whats your opinions guys.

[Ba82Ep3]

Well the EP has EBD (electronic braking distribution) and what you are feeling is most likely the system trying to compensate for the MC (as mentioned) going bad.

Before you changed the booster, was there a stain under the MC on the face of the booster? If so that is a tell tale sign of MC failure. Oddly enough an MC failure is usually the cause of booster failure.

You did grease all caliper pins before reassembly as well?

[apexracing]

Well the EP has EBD (electronic braking distribution) and what you are feeling is most likely the system trying to compensate for the MC (as mentioned) going bad.

Before you changed the booster, was there a stain under the MC on the face of the booster? If so that is a tell tale sign of MC failure. Oddly enough an MC failure is usually the cause of booster failure.

You did grease all caliper pins before reassembly as well?

no stain on booster and no fluid between booster and master. and the front calipers and brackets are new and greased, the rear brackets have new boots and fresh grease.

so my reversing of the booster vacuum line killed the booster which in short killed the master? is the new booster i installed in any danger then?

[Ba82Ep3]

And you are bleeding from the drivers front clockwise around the car?