dual diaphram brake booster upgrade problem *UPDATED*
 

you can skip down to the line where i explain my problem if you dont want to read my intro.

ok so for the past few weeks my driver side brake caliper will some times compress and when i let off the break pedal it wont uncompress making my break pads start gripping and after a little bit they will start smoking.

so the other day i started to bleed my breaks, and i noticed that i was leaking break fluid between my master cylinder and the break booster, so i figured that it was time to upgrade to a dual diaphram break booster. i found a break booster and a master cylinder at my local scrap yard for $22, it was in a 99 cherokee.

after many trips to the auto parts store i got all the adapters and break lines and installed the break booster. i did not space out the booster 1/4 inch like some tutorials on the internet say to do. i guess i should have becasue my break booster is pushed into my break light switch kinds hard.

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so finally i went to blead my breaks, i started in the back and, i had my friend pump the pedal, but no fluid came out of my bleader , so i unscrewed the bleeder even more and still no fluid. so i tried the driver side and still no fluid. so then i tried the front, and they worked fine, fluid squirted out just fine.

i tried to check all the lines and i could not find any crimped break lines

so my question is what could be causing this? a clog in the break line, the master cyliunder/break booster i bought is bad?

any help would be greatly appreciate, i need to get my jeep running so i can get to college.

if you need me to explain any thing about what i did just let me know.

josh

its possible that you need to bench bleed the master cylinder since it went dry during the whole process. Had that problem with a used master once. that will also tell you if your getting pressure out of the master to the rear brake lines.

It takes time to get fluid to a rear wheel, espescially when the system is is disconnected and not "gravity bled"

I believe you have an airpocket somewhere, and pumping the pedal is just moving it back and forth. Open the bleeders at the rear wheels and let it sit till it start dripping out.

before that though bench bleed the master cylinder... which can be done in the Jeep if you have the hose kit.

That 99 booster to your 92 sounds suspect as well. From my research before doing this job you needed a 95-96 booster to fit correctly. Without that spacer you may not be getting full travel in the brakerod meaning your not getting the proper "boost".

you don't need a spacer. the only reason they use a spacer is so the brake rod/pedal is near stock location as the 99 has a longer rod.

i've done this with my 90 using a 99 booster and didn't use a spacer.

just bleed out the brakes starting with the wheel furthest away from the master and so on.

it may take a bit as mentioned.

ok so i bench bled my master cylinder today, i tried to get the master cylinder as level as possible by jacking up the rear end, it was still not completely but was pretty close, i pumped the breaks for about 30 sec untill i could see no more air bubbles coming out. i then again tried to bleed my breaks, and i still have no fluid getting to back of my jeep. so then i decided to gravity bleed my system, i took out all the beeder screws, and filled up the reserovir and put the cap back on, my jeep has been sitting for about 3 hours now and no fluid has come out, if i press the break pedal fluid will squirt out the front two bleader holes, but still nothing at the back. how long should it take to gravity bleed my system?

When gravity bleeding you're only supposed to crack open one bleeder screw at a time, and leave the MC cover loose so it isn't working against suction. Start with the RR, then LR, then RF, then LF. When fluid drips to the ground, close that bleeder and go to the next one. Make sure and keep an eye on the brake fluid level in the master cylinder and keep it topped off.

i have a question, if i do a reverse brake bleed, when you pump the fluid in from the bleeder screw, would that also bench bleed my master cylinder? because it would pump all the air out?

I've never heard of doing that.

You can bench bleed the MC on the vehicle by using short lines from the MC outlets back into the reservoir under the fluid. When you see no more bubbles, it should be good. Just go real slow with the pedal the same as you would on the bench. Then hook up the brake lines and do the gravity bleeding. Follow that if needed with regular or power bleeding.

To answer your question simply - yes, it will "bench bleed" the master since you would be forcing fluid from the wheel cylinders to the master. This is a procedure known as "power bleeding" and works well, however there is the possibility to force any built up residue/garbage that is resting in the wheel cylinder/caliper/brake line up and into the master cylinder which would quickly wipe out the master cylinders seal.

If you want to power bleed the brakes I would suggest presurizing the master clinder and bleeding at the bleeder screws or using a Mityvac brake bleeder kit suck the fluid out.

http://www.sears.com/shc/s/p_10153_1...0070921x00003a

You can power bleed with a unit designed for this. Snapon and OTC make power brake bleeders as well as other companies. You Can Not Reverse Bleed the brake system. You will cause several problems.

Bench bleed the master and then purge bleed the rears . Open the bleeder screw first push the pedal to the floor then close the bleeder. repeat this several times till you see brake fluid at the rear. Then you can go back and bleed the brakes by pumping the pedal a few times , holding it down and open the screw.

Have you made 110% sure that there are no obstructions in the near break line?

i'm not sure if there is any obstructions, that is part of my problem, i tried to take off the hard line that goes to the rear, but it is seized up and wont budge.

i open the rear bleeder screw and when i step on the pedal the pedal stiffens up until i cant press down any more, (like it normally would if my jeep was off and my bleeder screws were closed.)

is this the symptoms of an obstruction in the line, or could this still be air.in the system making it so i cant bleed my breaks?

thanks for all the help