Rear Brake issues( Drums )

[jps4jeep]

Couple things, if the lines at the master were removed and then reattached, you will need to bench bleed the master prior to bleeding the individual wheel cyclinders. if not, when you bleed at the wheels you will get steady fluid even though there is still air in the line.

a seal between the master and boost does not mean anything as to the firmness of the pedal and the efficiency of the brakes. the booster is simply to assist in the braking and has almost no effect on peddal firmness.

Of you are getting brake fluid from between the master and booster, the primary seal on the master is junk. they are cheap to replace, but a ***** to do, at that point might as well rebuild the entire master.

I suggest starting from scratch. Bench bleed the master, starting at the rear pass, bleed at the wheels, after you do so, repeat. if you have access to the equipment, you can power bleed.

Lastly, I have found on all the 88-98 trucks that I have owned that in the rear near the spare tire where the line turns down to the rubber line, the line will have a hair line crack, causing fluid to shoot up behind the bumper, causing soft peddal and is hard to diagnosis since the fluid will not drip.

 

[shelbyt.67]

If u have the RWAL I would highly suggest removing it before u throw anymore money at it. Removing it may work yer miracle.

 

[Swims350]

mines removed. it's what started this whole mess, that and replacing the front flex lines, then twisted rear hard lines in 2 so i got new lines front and rear.

 

[DGA1]

Booster: With the truck off, pump up the brake pedal till it's firm, step on it hard and if it keeps sinking your booster is bad.

Master Cylinder: With the truck on, pump up the brake pedal till it's firm, step on it with authority and if it keeps sinking all the way to the floor you have a bad MC.

Mind you, before the MC test I'd make sure the fluid coming out does not have any bubbles in it.

 

[Swims350]

never heard that on a booster, only heard when it's bad it's gonna stay hard all the time, as far as pushing the pedal and not be easy when it's running.

mine does that tho, pump em with engine off, gets hard, stays hard, let off and hit em again and it falls to the floor.

engine on you can't pump them up, makes no difference. They go to the floor.

 

[outalne94z71]

ummm, bad master will fall weather the engine is running or not, bad booster stays hard and no assist.

chris what you describe i would put money on as a bad master

 

[Swims350]

same here buddy, it's my next thing to change for sure.

 

[DGA1]

ummm, bad master will fall weather the engine is running or not, bad booster stays hard and no assist.

chris what you describe i would put money on as a bad master

I diagnosed my bad MC with the little procedure I wrote above, maybe 6-months ago. Pumping up the pedal to get it firm when the truck was off and in all honesty it did not fall no matter how hard I stood on it, with the truck off. With it on, it was a whole other story, I could pump it up and get it firm, but if I pressed on it hard it would just keep sinking.

 

[Swims350]

mines the exact same except it will NOT pump up with the truck running. That's mine tho, not everyone else most likely. Then again IMO ANYTIME you HAVE to pump up the brakes, something is wrong.

 

[outalne94z71]

I diagnosed my bad MC with the little procedure I wrote above, maybe 6-months ago. Pumping up the pedal to get it firm when the truck was off and in all honesty it did not fall no matter how hard I stood on it, with the truck off. With it on, it was a whole other story, I could pump it up and get it firm, but if I pressed on it hard it would just keep sinking.

the booster was just enough assist to get the master piston seal to fail, with it off the seal must have just been strong enough to be stronger than plain foot pressure.