Ok i'll make this as short as possible.

92' LS 160k miles

The brake pedal was very smushy and if stopped the pedal would sink to the floor after a few seconds. So my thought is, "ok need a new master cylinder"....so i go to the local salvage yard and get another MC and it's in really good shape, looked almost brand new. even in the resivoir it was clean.

So i put the MC on and bench bleed it before i put it on and then bled the **** out of all corners, and then take it for a spin and it seemed better at first but i knew it wasn't fixed. The pedal was still not very firm.

Then at a light today i start to feel the pedal sink to the ground again.

Could this be something else?? what would a bad prop valve do?

any response is welcome and apprietiated

 

i know everyone has had some brake issues one time or another

 

first of all i am a mechanic with certifications one being brakes, just so you know im not guessing. the problem you are describing is the master cyling bleeding down internally. this has happened on both of my integras and my accord it is common on hondas. one of the few common honda problems. dont use used master cylinders there is no way to tell if the one your getting is better than the one you have. if you get a good used one it will go bad b4 long. i have experienced this on many hondas and other cars. just get a new if you can afford it if not buy a rebuilt and if it goes bad return it and get another one. you dont have to bleed the brakes at the wheels when you put on m/c just bleed it at the m/c by cracking the line loose and have someone push pedal if you want to go further go to next available fitting i believe is at prop valve have to look to remember but bleed there if you want to. but do bench bleed.

 

well thanks so much for reading my drawn out post.

It's not really a big loss, i only paid 15 bux for the master cylinder. Only a loss of my time i guess.

So it's definately not the Brake booster? correct me if i'm wrong, but wouldn't the pedal be REALLY firm if the booster was bad? Like as if the car wasn't on and you pressed the pedal?

I'd just hate to go buy a brand spankin new MC to have the same problem and wasted money twice.

I'm not saying i don't trust you, i just want to be positive.

Can a prop valve go bad? what would happen if one did?

thanks again agrn93ls

 

all a booster does is boost pressure to the m/c want to test yours? turn off engine and push pedal 3+ times then will be really hard that is simulating bad booster. so yes your correct. or clamp the vacuum line while engine is running so you feel like everything is the same as while driving and use brakes same thing will happen. i have done way too many m/c's too not know. now to be honest i have never really had to replace a prop valve. but im positive of what a bad m/c does mine is doing it now. i recently replaced my friends on his integra with the same symptoms. it fixed it. a bad prop valve would change the way your brake works not the pedal. a sinking pedal is only due to pressure loss in the lines by either air or the m/c bleeding down internally past the seals unless you have a fluid leak and the fluid is coming out while holding the pedal down. think about it the m/c pushes pressure into brake lines if there is no air and no leak where is the pressure going? the seals in the m/c are bleeding fluid internally so there is no leak. and yes i know they are expensive even rebuilt from O'Reilly or whatever which is what i used on friends car rebuilt one, that is why mine is still bad i just deal with it because it is intermittent

 

So your saying that if i have no leaks(which i don't) your even more positive of the MC.

Getting a new one is no problem, so i guess i gave myself something to do this weekend coming up lol

thanks a ton again
DAguyLS

 

yes that is what im saying AND if you dont have air in the lines but if you have air the pedal will always feel squishy/soft/low unless you pump up alot of times fast. the way to test a m/c is to have a good pedal then stop and hold with moderate pressure not a lot and if pedal slowly goes to floor then you let off and push and it feels good right at first then you can pretty much bet money.

 

yea thats pretty much the case here.

apparently the one i picked up fromthe j-yard was "better" but still faulty.

it's definately less spongy than the original one, but if i come to a stop and hold the car still it still sinks but not right away and not as fast as it was before.

So i'll be getting a new MC, just not sure if i should go to the dealership or local parts store.

I saw from local parts store they have a raybestos MC that was around a hundred bucks. I'm wondering what the dealership wants for a new one.

 

well i dont remember the brand i put in my friends car but i do know that at the shop i have used raybestos parts and they are good, i have the best experience with raybestos brake pads over any other brake aftermarket pads. and if you buy one from the auto store and it goes bad its usually easy to return for another. dealer parts are always best and usually expensive but do check. i dont think i would go to the dealer because im sure they are probably real expensive. and when you go to the auto store they will sell rebuilt or new ones in aftermarket brands use new at the shop i have had problems with rebuilt m/c's not with new. later man and good luck. and props on the second gen i miss mine terribly, had a green ls special with leather and a FACTORY center console/arm rest/cup holder, try to find one of those. oh and one thing always use acura brake pads they kick *** for stopping power i have axxis ultimate road/race on my 95 GSR no better than OEM that i can tell.

 

Actually this is my girls car....she came home today and said the MC i put in still isn't working right.

center console arm rest cupholder...wow...nice.

Word up for being the only guy to help me out.

peace bro
DAguy

edit: She likes to think it's her car....it's really mine, she just drives it haha