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View Full Version : 03 si brake pedal goes from firm to really low in two pumps.



apexracing
08-07-2011, 11:02 AM
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
08-07-2011, 01:06 PM
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
08-07-2011, 01:15 PM
It sounds like it just needs to be more thoroughly bled. Hope that does the trick.

apexracing
08-07-2011, 01:35 PM
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
08-07-2011, 04:12 PM
Run a vacuum line from the bleeder valve and submerge the other end in brake fluid. You shouldn't need special tools.

apexracing
08-07-2011, 05:14 PM
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
08-07-2011, 06:35 PM
bad master cylinder

27rocks
08-07-2011, 07:27 PM
bad master cylinderI'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
08-07-2011, 07:47 PM
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
08-07-2011, 07:52 PM
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
08-07-2011, 07:54 PM
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
08-07-2011, 08:15 PM
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
08-07-2011, 08:22 PM
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
08-07-2011, 08:24 PM
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
08-07-2011, 08:28 PM
And you are bleeding from the drivers front clockwise around the car?

apexracing
08-07-2011, 08:37 PM
And you are bleeding from the drivers front clockwise around the car?

yupper following the helms manual, btw i did not remove the lines from the master to change the booster. is it possible for the master to be bad without having fluid between it and the booster?

Ba82Ep3
08-07-2011, 08:44 PM
Well anything is possible. And if you're bleeding the system properly then there really is only one other thing it could be... a bad MC.

You said you were pushing the brakes hard enough to actuate the ABS... does it soften up AFTER that?

apexracing
08-07-2011, 08:48 PM
Well anything is possible. And if you're bleeding the system properly then there really is only one other thing it could be... a bad MC.

You said you were pushing the brakes hard enough to actuate the ABS... does it soften up AFTER that?

yup i was told it was proper to actuate the abs before a bleed. and nope got firmer actually then soft again, just comes and goes. my booster was rusted along the bottom but it had 200k on it. and shit didnt hit the fan untill my booster vacuum line fuck up.

Ba82Ep3
08-07-2011, 08:56 PM
Well it ensures a solid push of brake fluid through the ABS block. With it getting firm after ABS actuation then the pump is working fine. But for the pedal to get soft again... what are the odds you got a shitty booster? Do you have to repeatedly pump to have brakes or do you have brakes and they just lost their initial bite after ABS actuation? No hiss sound at the brake pedal?

apexracing
08-07-2011, 09:00 PM
no the first pump or two feel ok then it goes soft, but after repeated use its just low. then while driving can feel better ya know. but for the most part its low, even with or without the abs kicking in.

but the symptoms are different with the new booster, since the pedal feels normal sometimes, and before the pedal would build pressure just by sitting idle then after a push would be super soft. idk i should of just replaced both at once i guess.

beechstreet
08-07-2011, 09:09 PM
so you already replaced the booster? I'm sticking to bad MC. I recently did the MC on an 02 EM2 that had the same symptoms. Problem solved.

apexracing
08-07-2011, 09:11 PM
so you already replaced the booster? I'm sticking to bad MC. I recently did the MC on an 02 EM2 that had the same symptoms. Problem solved.

roger that already replaced the booster. where did you get your master from? i'm thinking of just getting a reman from autozone as they can get it to me faster.

beechstreet
08-07-2011, 09:15 PM
roger that already replaced the booster. where did you get your master from? i'm thinking of just getting a reman from autozone as they can get it to me faster.
I work at a small shop, so I got it through WorldPAC, otherwise I would have gone to Napa

apexracing
08-07-2011, 09:49 PM
i guess ill order a new master cylinder when i get paid this friday, ugh

Ba82Ep3
08-08-2011, 05:18 AM
WorldPAC is the same as CarQuest, as Autopart International is the same as Advance Auto. I love WorldPAC tho... AI dreams they were that good...

Im stickin with MC too. For future reference tho, its usually best to swap the MC with the booster. Its a little more costly up front, but think of all the frustration and TIME you could have saved doing it only once. :mwink:

Keep us updated!

apexracing
08-08-2011, 07:51 AM
yea i just figured my vacuum goof damaged the booster, i didn't even think what it could of done to the master cylinder over time. but i'm parking the car this week, and ordering a new master on friday. i'll keep you all posted.

beechstreet
08-09-2011, 06:43 PM
WorldPAC is the same as CarQuest, as Autopart International is the same as Advance Auto. I love WorldPAC tho... AI dreams they were that good...

I love WorldPac. It's saved my ass countless times!

Ba82Ep3
08-09-2011, 07:38 PM
I dunno if you have ever heard of a company called BapGeon before... but they do import parts only. Between them and WorldPac... you cant go wrong.

Bap sent me a radiator from Norfolk, VA to Orlando FL in ONE DAY at no extra cost. 95 Civic, plastic tank split and left me stranded with no one local having the rad. I swapped it out in the parkinglot the following morning and was on my way!

beechstreet
08-11-2011, 07:26 PM
I dunno if you have ever heard of a company called BapGeon before... but they do import parts only. Between them and WorldPac... you cant go wrong.

Bap sent me a radiator from Norfolk, VA to Orlando FL in ONE DAY at no extra cost. 95 Civic, plastic tank split and left me stranded with no one local having the rad. I swapped it out in the parkinglot the following morning and was on my way!

I haven't heard of BapGeon, but doesn't look like they have any locations in or around California.

So did the MC fix the problem?

apexracing
08-16-2011, 11:37 PM
yup installed and bled today and bam back to new. thanks guys!

Ba82Ep3
08-17-2011, 12:35 AM
Awesome... glad you got it fixed! Now you can head to the BBQ!! lol

beechstreet
08-17-2011, 01:05 AM
nice! glad to hear all is well

andyman97
08-17-2011, 04:03 AM
Good deal, glad you got it fixed.