Topic: Bleeding rear disc brakes. Can't get all the air out.

[alwayzbroken]

I replaced the entire brake system on my 92 SAS P/U. I installed rear discs with 85 monte carlo calipers, Fj80 non-abs master cylinder. Eliminated the proportioning valve. I have fluid in the front calipers but cannot get pedal or fluid to the rear calipers. Is there anything with the residual pressure valve in the master cylinder that makes bleeding the rear circuit in master cylinder difficult? Any special process or do I have another problem? Please help. Thanks.

[DAWGTOY]

hey broken
 did you bench bleed the master ? if not do it.
you should have no problems.

[alwayzbroken [OP]]

I tried to bleed the master on the truck. I am gonna try to bench bleed it tonight.

[germ]

What I've done in the past, is fill the reservoir, and open one bleeder on the back, and go drink a beer until brake fluid starts to drip out. Then close it and go open the other side, and have another beer. Once that starts to drip, you should be ready to do a regular bleed process. Works like a charm, and doesn't require any special tools or tricks, just a few beers.

Erik

[alwayzbroken [OP]]

What I've done in the past, is fill the reservoir, and open one bleeder on the back, and go drink a beer until brake fluid starts to drip out. Then close it and go open the other side, and have another beer. Once that starts to drip, you should be ready to do a regular bleed process. Works like a charm, and doesn't require any special tools or tricks, just a few beers.

Erik

I opened the bleeder screws and let them sit all weekend before attempting to bleed them on monday. The fronts had fluid but not a drop had reached the rear calipers.

[germ]

Hmmmm, not sure what to make of that...Could there be a blockage of some kind in the brake line? Might want to check the MC, to make sure it's not clogged or something.

Try going backwards thru the brake lines, and make sure everything is connected correctly, and no blocked. Other than that, I don't have much for a suggestion. Did you tighten the fronts before letting the backs bleed? Could be the fluid is taking the path of least resistance...ie the fronts.

Good luck,

Erik

[79coyotefrg]

did you take the load sensing proportioning valve off, or just unhook the little bar,  cause you have to completely bypass it   to make it work,  other wise the fluid will get to the proportioning and stop

[79coyotefrg]

who is helping you bleed the brakes??

[alwayzbroken [OP]]

who is helping you bleed the brakes??

An ASE certified tech who is equally confused, but has a few tricks up his sleve still.

did you take the load sensing proportioning valve off, or just unhook the little bar, cause you have to completely bypass it to make it work, other wise the fluid will get to the proportioning and stop

The proportioning valve is gone. I am going to try and bench bleed the master again. I hooked up a MityVac handheld vacuum pump to the rear hose before the axle and pumped for about 20 minutes drawing mostly air and some sporadic bubbles of brake fluid. Far from a constant stream of fluid. After that, we attempted to bleed the right rear caliper and got no where.

[alwayzbroken [OP]]

Hmmmm, not sure what to make of that...Could there be a blockage of some kind in the brake line? Might want to check the MC, to make sure it's not clogged or something.

Try going backwards thru the brake lines, and make sure everything is connected correctly, and no blocked. Other than that, I don't have much for a suggestion. Did you tighten the fronts before letting the backs bleed? Could be the fluid is taking the path of least resistance...ie the fronts.

Good luck,

Erik

I will check everything out in great depth tomorrow. I sure hope it isn't something stupid like a loose hose somewhere. I checked already and didn't find anything. I don't know if it is possible for the fluid to drain to the rear since the line makes an abrupt turn and goes up over the brake booster. Will brake fluid still gravity feed up over the booster?

[BUBBA]

Are the calipers mounted with the bleeder's on top?
If not you will never get them bled.

I  I don't know if it is possible for the fluid to drain to the rear since the line makes an abrupt turn and goes up over the brake booster. Will brake fluid still gravity feed up over the booster?

As long as the line isn't about the resevoir it should still gravity bleed just fine.If it is,it's still possible but only if all the air is out of the line.

[alwayzbroken [OP]]

Are the calipers mounted with the bleeder's on top?
If not you will never get them bled.

The bleeder screws are mounted up.

[alwayzbroken [OP]]

Where is the best place to mount a proportioning valve. I received my Wilwood proportioning valve today from Summit and don't know the best mounting location. I would assume the closer to the master the better, but I don't really know. Any ideas?

[McWilly]

The bleeder screws are mounted up.

Can you get a pic? I just did mine and the orientation that I set my bleeders at worked great (calipers in front of the axle, bleeders on top, pointing towards the back, 5-10 degrees above horizontal).

[79coyotefrg]

   i cant imagine what you guys are doing, ihave never ran into a car or truck, disc or drum brake system that wouldnt bleed if done properly,   

ase  is a good thing to have , but tests have passing grades and failing grades,  i once showed one of my instructors how i was shown to bleed brakes by my dad and his response was "thats usually not nesssecary" 

i have always done my bleeding with someone else in the truck/car and me under the vehicle,  with a foot on the brake pedal and a wrench on the bleeder

push pedal -release bleeder- tighten bleeder-release pedal and pump-then hold and repeat

[Northern Runner]

I mounted my Willwood valve right beside the master cylinder.
I had the same problem that you are experiencing. I found that my issue was the ABS module for the rear diff. Its mounted on the passenger side frame rail. I replummed the brake lines to bypass the module and removed the ABS bulb from the dash. I also installed a Willwood residual valve to hold the line pressure and the system works great now. It seemed that the conversion put the ABS system into bypass mode and would not send fluid to the rear brakes.
Hope this helps.

[alwayzbroken [OP]]

I mounted my Willwood valve right beside the master cylinder.
I had the same problem that you are experiencing. I found that my issue was the ABS module for the rear diff. Its mounted on the passenger side frame rail. I replummed the brake lines to bypass the module and removed the ABS bulb from the dash. I also installed a Willwood residual valve to hold the line pressure and the system works great now. It seemed that the conversion put the ABS system into bypass mode and would not send fluid to the rear brakes.
Hope this helps.

I never thought of ABS. I will check that out when I get home from class. Are you using the FJ80 master cylinder as well? Is additional residual pressure needed other than what the FJ80 master cylinder supplies?

[79coyotefrg]

abs     didnt think of that,  did you use a abs mastercylinder

[alwayzbroken [OP]]

I checked, I used a non abs 4wheel disc master cylinder and the truck does not have abs. Back to square one. I will not sleep friday night untill I figure it out. One way or another the truck is going to have brakes this weekend.

[BUBBA]

Something you might try,open bleeder,push pedal to floor,close bleeder.repeat.
I have used this method before with good results.

[alwayzbroken [OP]]

Something you might try,open bleeder,push pedal to floor,close bleeder.repeat.
I have used this method before with good results.

Thanks smart a$$

[toynorcal]

Not sure if you've tried this or not. But Gravity bleeding one caliper at a time is a good way to get more pedal.    Good luck man

[BUBBA]

Thanks smart a$$

   I wasn't trying to be.

Have you checked to see if any fluid is coming out at the M/C.May have gotten a bad M/C.

[RHG]

Not sure if you've tried this or not. But Gravity bleeding one caliper at a time is a good way to get more pedal.

How is this done, I dont think I have ever heard of that.

[79coyotefrg]

How is this done, I dont think I have ever heard of that.

hes talking about just opening the bleeder on one caliper and letting it sit over night, 
one person hold the pedal ,one person work the bleeder

[RHG]

  Gotcha, I am going to have to replace my booster and/or MC soon I think. Where they meet is really corroded and I recently got a mushy pedal. Only takes one pump to get it back again but thats no good, especially with the rainy season coming. I need brakes.

[79coyotefrg]

yea , you'll be like that little orange dude in your avitar pumpin them brakes

[Northern Runner]

Well you got me. I am using the stock m/c, I installed a prop valve and a residual valve because I found my brakes to be spongy.

[reklund5]

Any chance the Monte Carlo calipers are stuck?  What happens if you disconnect the line from the caliper- then can you use the mityvac to draw fluid?

Ryan

[alwayzbroken [OP]]

Any chance the Monte Carlo calipers are stuck? What happens if you disconnect the line from the caliper- then can you use the mityvac to draw fluid?

Ryan

I checked the monte calipers, but they are brand new and not stuck. My buddy came over after work and we bench bled the master again. But he had to leave before we could bleed the brakes. I had another friend come over and we started bleeding at the right rear and worked for a very long time and couldn't get anymore than a few drips of fluid to come out. I hooked up my mityvac to the rear brake line and pumped for about 20 minutes and only got air. I cannot figure out why I cannot get a solid supply of fluid to the back. You can pump and unscrew the bleeder all night and not get even the slightest feeling of pressure. I have the brakes gravity feeding right now overnight in hopes that something favorable may happen tomorrow. The front brakes are bled, no air comes out just fluid but I still have zero pedal pressure. While bench bleeding it was noticed that the master cylinder felt like metal on metal contact inside. I am wondering if something is not right with the master.