WTF brakes not working after replacing the Master cylinder!!

DigitalDUST · Oct 13, 2003

it was working the whole time then all of sudden I lost pedal pressure. it just goes all the way to the floor with only slight pressure near the floor ,, I can barely brake at all!! so i bought a new master cylinder and replaced it.. and I bleeded it , all around 4 calipers.. watching for leaks , there were NO leaks. so I test drove it.. STILL THE SAME!! no pressure on pedal. just goes all the way to floor with slight braking resistance. what did I do wrong? what is other possiblities that could cause it?

i know theres only booster, master cylinder, lines, calipers and pads! Ive checked everything for leaks, cracks etx.. nothing! anyone with that experience. pls help me!!

PIONEER · Oct 13, 2003

sounds like a pressure problem. Take the cap off, start car and pump brake like hell. Sometimes if there are bubbles in the system, they come to the top this way. Good Luck

Guest · Oct 13, 2003

I just rebuilt my master cylinder today

You need to bleed the master separately, which was a surprise to me, until I read the TSRM.

Follow the instructions on this page:
http://www.cygnusx1.net/supra/library/TSRM/br/BR_06.html

Unfortunately you'll have to re-bleed all your brake calipers after wards.

Hope that works for you.

BoostAddctn · Oct 13, 2003

Shawndude said:
I just rebuilt my master cylinder today

You need to bleed the master separately, which was a surprise to me, until I read the TSRM.

Follow the instructions on this page:
http://www.cygnusx1.net/supra/library/TSRM/br/BR_06.html

Unfortunately you'll have to re-bleed all your brake calipers after wards.

Hope that works for you.

yups, what i did was i filled the master cylinder up with fluid, then i pushed it against a wall until all the air was gone and a steady stream of brake fluid came out, aight good luck man, peace

cullen · Oct 13, 2003

take it off and bench bleed it. the box the new one came with should have instructions on how to do it.

DigitalDUST · Oct 13, 2003

DUDE!!

take it off and bench bleed it. the box the new one came with should have instructions on how to do it.

thats exactly what I did!!! i bench bleeded it until there were no air bubbles. then installed back on.. still the same problem. this is why I posted this thread!

Guest · Oct 13, 2003

it will work just keep tryin and do the bench bleed or you may have air some where in the system and it dose not want to leave

Mr. Sinister · Oct 13, 2003

Does your car have ABS? If it does, there may be air trapped in that system. You'll have to get the car up to ~15mph or so to get the ABS system going and then re-bleed.

DigitalDUST · Oct 14, 2003

Does your car have ABS? If it does, there may be air trapped in that system. You'll have to get the car up to ~15mph or so to get the ABS system going and then re-bleed.

no dude. I removed my abs... Im gonna rebleed my master cylinder once again and see the results.. this sucks!!

Guest · Oct 14, 2003

Did you get it figured out?

Unfortunately I'm thinking bleeding of your master cylinder may not help in your case. I put mine in without doing any bleeding, and it worked fine right away. I bled it after I read the TSRM.

What happens if you press the pedal down repeatedly like 20-30 times? Do you loose any brake fluid from the reservoir?

It really does sound like you have a leak somewhere, since it happened so suddenly even before you replaced anything.

DigitalDUST · Oct 14, 2003

yes I checked the lines for any signs of leaks and the fluid is still there. it never will go empty.. that means theres no leak. not even a puddle under my car. ive pumped the brakes while parked and looked under. even removed my tires and had someone pump the brakes while i watch the lines and caliper do the work. nothing at all!!!

either there must be air in the system.. I have replaced many master cylinders. it requires bench bleed first before install but this is my first time it didnt work!! I sure hope I didnt get a defective one!!

soup · Oct 15, 2003

tap the proportioning valve while bleeding the rears. i don't know how the hell i got some air in there but it's a biotch to get out.

DigitalDUST · Oct 15, 2003

tap the proportioning valve while bleeding the rears. i don't know how the hell i got some air in there but it's a biotch to get out.

i dont understand what u mean.. where is the "proportioning valve" is that the screw in the middle section that seems plugged???

soup · Oct 15, 2003

http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/291420/4708_1.html
you can see where all the different lines go. 47322 looks like the one to the rear brakes. get a buddy to pump the brakes and tap that whole proportioning valve assbly and the lines, somehow air gets caught up in there.
hth

Flywest · Oct 16, 2003

Ok, my take certainly sounds stupid but listen to this :
Last year I was losing the brakes often, like no pressure at all on the brake pedal, especially after cruising or boosting. We couldn't figure out what was the problem and we looked everywhere. I had an exhaust leak for a while ( resonator had a huge chunk that had popped off ) and decided to get it fixed. Got that resonator out of there and replaced it with tubing. A few days later I still had not lost my brakes once and never lost them since.

So if you have an exhaust leak, you might check that out for what it's worth .

BoostAddctn · Oct 16, 2003

maybe your brake booster went out? how do we check those anyways? aight peace

Guest · Oct 16, 2003

BoostAddctn said:
maybe your brake booster went out? how do we check those anyways? aight peace

Brake booster failure will only result in hard to press pedal. It will not cause the pedal to go all the way to the floor, without brakes being applied.

To test the booster:
http://www.cygnusx1.net/supra/library/TSRM/br/BR_06.html

WTF brakes not working after replacing the Master cylinder!!

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