so yesterday i had the joy of replacing my brake lines because it poped about a foot before my rear tire. anyways, we go to bleed the system, and i cant get any pedal pressure, and it seems like we cant get the air out of the system, like it just keeps putting more in. no leaks in the lines anywhere, dont hear any air coming out either.

so we take a look under the hood, and my buddy watchs the MC as i pump the brakes. after a few pumps u can see it kind of cycle the fluid back, but there is no pedal pressure, and u can kind of hear a sucking sound (possible vaccum leak?) coming from the MC.

im really looking for help here guys. searching told me its most likely the MC untill i read how to test the brake booster (and im not getting any pedal pressure)

i really dont want to replace both, im gonna try the MC first. any other ideas?

 

ok here is what u do, the brake booster is only an assist, if u had a faulty booster than ur pedal would be as hard as a rock.
first replace all the bad and leaky brake lines,
after that is done fill up the master with fluid to full
than go and open all the bleeder screws so it will gravity bleed itself (now u take lunch while this is happening) never let the master run dry
after about 20 mins come back and close all bleeder screws on all wheels
than let your buddy or anyone pump the brakes while u do a manual bleed u know the procedure of that I assume
good luck

 

thats what we did (all except the gravity bleed), and we bled them for like 20 minutes.

ive got a remanufactured MC coming into carquest tomorrow morning at 11. so we shall see if its that.

 

havnt gotten the MC yet, anyways...

from talking to people im pretty sure the boost is fine. its a little weird that the MC decided to go right when i broke a line, so i was told to bleed the MC.

i think i'll just be shooting myself in the foot if that works, cause judging from my luck, its on its way out, and it could go out at a bad time.

hopefully i'll be able to replace it tonight

 

I would suggest bleed the MC before replacing it. To bleed the MC disconnect the two brake lines connected to it and run a hose from where the lines connected to and route it back to the MC. By doing this it takes all the air out of the MC it self. I did a 5 lug swap and it took me forever to get pedal pressure again. Good luck!

 

was just told to bench bleed the MC.

what is bench bleeding?

 

nevermind


tonight, we got pressure in the lines, but we are still drawing in air somewhere.

pretty much convinced the MC has air in it, so tomorrow im getting tubing to bleed that.



on top of that my light switch went again tonight

 

How are you bleeding? The "hose in a bottle" bullcrap, or something else?

 

hose in a bottle has worked for me. is there some other way? ANd Wayne for a newb you sure have alot of posts and alot of knowledge, mad props. Stick around as long as some of the other guys with the good knowhow and you will have 20g posts

 

well, we havnt bled the MC yet. i was figuring on just putting a hose on the outputs, and putting it right back into the MC through the top.

is that wrong?

 

Running the hoses back into the MC should be fine for bench bleeding. Be sure to keep them submerged so the don't draw air back into them. I've seen the MC go bad after a brake line failure several times. Over the years, deep into the bore of the master cylinder developes rust. When the brake line fails, the pedal goes closer to the floor than it's ever been. This drags the seals on the piston in the MC through the rusty portion of the bore. That rust will often tear the seals or lodge into the seals causing the fluid to pass through. End result....Pedal goes to the floor, unable to build pressure. On older vehicles, even if I'm only changing brake pads, I cautiously press the brake pedal only about half way several times until a firm pedal is established. I've had good luck since. Dave C.

 

Oh wow heres a topic for something I've actually done before. Ok after you replace the brake master cylinder (MC), you are gonna have a ton of air in it comeing through the lines. I bleed each brake caliper seperatly and then once again after I had pedal pressure. I think the gavity bleed idea will help in doing this but I've never done a gravity bleed before. Okay so heres the deal, that pedal will go straight to the floor with no cahnge until the very end of the process. Bleed air from one caliper starting from the one farthest from the MC. Bleed all the air and then just a little more for good measure and cause the old fluid looks crappy. Add brake fluid so you don't go empty. Do the remaining brake calipers in order. When the last amount of air is gone from the last caliper the pedal will have stiffness again like it should.

I hope this helps you out.
-max

 

BIGGEST ******* PAIN IN MY *** EVARRRRRRRRRRRRRRRRR AHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!@@%#$@#@#)( @#_)(@#@)(#*@#@#!!!!!!!!!!!!!


still not bleeding, think i have it narrowed down to where the MC is leaking, but that means its time to pull the MC. and thats a ******* project and a half in its own.

sorry im not happy

/rant

 

yeah, i know how you feel hang in there... i had it worse than you. it will most likely be your MC because when you bleed and push on that peddel ALL the way to the floor, you might have just worn out a seal or something.(that's if you pushed it to the floor) put something under the pedal when bleeding the brakes and only go about 3/4th of the way down.

also, your FC might have 3 hardlines coming out of it, and not 2.

 

Sir Ruperts right, there are most likely 3 lines. One on either side and one on the bottom...that one is the pain. MC is not so bad I just hate brake fluid...it ruins everything. Oh use a lot of rags! Good Luck!!!

-Max

 

there is 3 lines. only bothered to bleed two before i found it leaking.

and yea brake fluid sucks