Cars 95 Civic I have GSR rear disc conversion, si 15/16 Master Cyl, stock brake booster, Teg 40/40/ prop valve, Stoptech braided lines, Stoptech Sport pads in front, Centric whatevers in rear. So pretty much last year all thats been done on car brake wise was replacing brake booster with a reman autozone unit cus the stock one was shot. The stock prop valve had a bad leak around the weep hole so I finally replaced it with a Teg 40/40 valve. The most recent thing I did was just replace rotors and front pads with Stoptech ones.

But my actual stopping distance and braking power I feel sucks right now and I cant figure out why. In the past when I had the Stoptech pads with the new 15/16 MC my brakes had so much bite it was ridiculous so i switched back to the Stoptech pads but still wasnt getting good results. I have no brake fluid loss, the prop valve is dry and the lines are all new and dry. I had bled the system last year after doing the steel lines and have decent pedal feel. I feel like the pedal still feels a little off like a tad spongy but it still engages high (which I like.)

I can feel the brakes engaging with a light push on the pedal but even if i like stand on the pedal I cant lock my wheels up its just a like gradual slow down. Dont even really feel the bite of the Stoptechs. Im thinking I may have a faulty caliper or the booster is a piece of crap or maybe the 40/40 valve is to blame...idk. Also under light braking I do feel a little shimmy in the wheel almost like one caliper is engaging before the other, leading me to think maybe one is faulty. Like i said rotors are brand new and pads and alignments good so the shimmys not coming from that.

 

prop valve problem - you'd still lock the brakes if you really try
faulty caliper - locking rest of wheels should still be possible (plus there should be signs of leaking)
booster issue - maybe

did you bed the pads on the rotors? bed in procedure

the light braking shimmy - does the car pull to one side or the other when this happens?

you may have air in one side.

 

I did bed them but only one cycle. If theyre not bedded correctly from the start will the rotor and pad be messed up for life of them? Ive been driving on them now for atleast 3-4 months

And yes the shimmy feels like a small pull to one side (not sure if right or left tbh) and it happens on the first braking during a drive, once the calipers have clamped down the next couple stops dont seem to pull unless its a super aggressive stop then I feel the wheel pull some too. So it doesnt happen every stop.

 

It sounds like you're not getting any boost from the booster.

The brake pedal should be much easier to press with the engine running than with it stopped. After you stop the engine it should be easy to press two or three more times, then get hard.

If it doesn't do that make sure the vacuum is reaching the booster. Disconnect the hose at the booster end and start the engine, there should be strong vacuum. The check valve may be installed backwards. The arrow on the valve should point toward the engine.

There is also a seal between the booster and the master cylinder that holds the vacuum in.

 

they are likely fine, the procedure is to get the max out of the pads. they've been working this long, don't break it.

since it does not happen every time, the minor pull to one side is something to look into later.

as mk378 said, brake booster is the most likely suspect.
It could also be a restricted line to the booster or faulty valve, your mention of "not every time" may suggest that the booster is getting some vacuum but not enough.
Could also be the brake master cylinder leaking into the booster.... how is the brake fluid level?

one last comment: I stopped doing Autozone parts on non wear items a long time ago. Their parts were always inexpensive but decent, but they have decreased their quality over the last 10 years. IMO NAPA or OEM Honda. (at last my local NAPA has not let me down, not all are the same)

 

Im going to check my booster when I get home because I think when I was installing the MC there was a gap a very small one between it and the booster and I tightened it down pretty tight and couldnt close the gap. I havent noticed any hissing though my car is super loud so idk

 

did you bench bleed the master cylinder?? You can't just fill it up with BF and expect no air in the unit

 

 

 

 

When i look down at my MC/Booster i can see a super slight silver of the pushrod but i tightened the MC plenty and was still left with this tiny gap.

 

There is supposed to be a gap there. If the master cylinder were to leak, the fluid can run out there rather than going into the booster and ruining it.

Did you do the test of engine running vs. stopped?

 

So pumping pedal couple times engine off can hear pumping noise (vacuum building?) gets marginally harder after 3-4 pumps. Engine on is slightly easier to press but overall pedal feel is the same. Had a couple inches more travel with engine running but it almost feels like the pedal hits a wall after that initial travel. I know from adjusting my pedal before that too high of an engagement had my brakes locking up and i re adjusted it back down. But when i installed the new booster i made sure the pedal was engaging in the right area

 

There should be a BIG difference engine on versus off.

Does the pedal go to the floor if you open a bleeder? There should be no "hitting a wall" until reaching the floor.

You may have some incompatible parts that don't work with each other.

 

 

 

 

There should be a BIG difference with vacuum applied to the booster versus not. It is normal to have to press the pedal very hard to stop the car when the booster is not working. This suggests that your booster is never working.

With no hydraulic pressure, the pedal should go easily all the way to the floor. If it "hits a wall", there is some mechanical obstruction in the booster / master cylinder assembly.

 

 

 

 

No ideas, but sure hope you figure out the issue!

 

https://www.hondaautomotiveparts.com...r-master-power

Make sure part #4 is in place, that it fits closely (airtight) on the sleeve on the back of the master cylinder, and that it is facing the right way (cupped side toward the MC). This is the seal that holds the vacuum in the booster.

The pushrod adjustment would not affect this situation. You want the pushrod set up so that the master cylinder goes all the way back when the pedal is not pressed, and also starts to move almost immediately when the pedal is pressed. A misadjustment too tight would make the brakes drag. Too loose and you will have more slack in the pedal before the brakes start to act. But the amount of force would be the same.

When you start the engine with the hose disconnected from the booster, it should suck a lot of air.

It is looking almost certain that your booster is bad though. There are no serviceable parts in the booster. Take it back and get another "lifetime" one.

 

 

That just isn't true. To start with the seal in the back of the master cylinder is inside a fair bit further, they will very much leak inside of the brake booster when the seal goes bad. That's not the pushrod you're seeing either, just part of the MC casting.

What did you order the master cylinder and brake booster for? You mentioned you have a 15/16s MC but didn't say what it was from, there's a few different versions. Did the master cylinder fit up against the brake booster like in the in pic on its own, or did you need to draw it in with the nuts?