WJ Booster/Master swap Issue.

[Megadan]

I just completed said swap.  The booster is used, but tested good and holds pressure perfectly.  I had to install it using washers to space it off the firewall as it wold not sit flush.  Spaced about 1/4".  Everything else mod wise related to the swap is perfect and operational.  The master I originally used was also from the same vehicle, but I discovered it weeping a tiny bit of fluid from the rear seal during bench bleeding, so I replaced it with a new (not reman) master cyl.  Bench bled that, installed, and bled the entire system 3 ways (gravity,pump up and release method, and a reverse bleeder.  So, I am pretty confident there is zero air in the system.   Even checked and adjusted the rear drums.  Also replaced all the rubber hoses in the system with new, longer, ones.

On to the issue.  When bleeding the front brakes only, the pedal would lose all ability to build pressure after releasing pressure during the bleed.  However, if you let it sit for just a few seconds it would come back and work.  Eventually we got to a point it would no longer do that seemingly and called it good.  Except that the front pads don't seem to fully let go of the rotors, a lot like the kind of drag you get with a drum setup.  I quintuple checked how the lines were run to the distribution block just in case there was some way that could F it up, and it matches the way everybody else did them.   

While driving, the pedal feels soft, but the brakes do grab almost immediately when touching the pedal.  It's almost like they aren't getting enough pressure.  But, if I push hard, the truck will damn near throw me out of the windshield.  The steering and truck still feel like the fronts are dragging.

The only thing in the system I didn't touch was the distribution block itself.  Was I supposed to do something with this?  
I am stumped.  Help...

 

[cruiser54]

How come you used spacers instead of modifying the firewall lip? 

[Dillithium]

So, this is a longshot, but I've had something similar happen to a friend of mine. Basically, he did everything what you did when installing a new master cylinder. He bench bled it and the bled all the lines in the vehicle. He first used the pump and hold method and used a little vacuum-pump afterwards. He could never get the brakes to work properly after installing the new master. I don't remember the exact symptoms, but there were pressure issues. What turned out to be the culprit was that he pushed the pedal all the way to the floor while doing the pump and hold method. Apparently, in new master cylinders, this can ruin internal seals. Thus causing pressure problems.

 

I never quite believed the story, mostly because it was the guy who sold my buddy the MC who came up with it. But after replacing it with a new one and just using the vacuum-pump, the problem was cured.

 

Other than that, you got enough fluid in the reservoir?

 

Still got the stock prop valve?

 

Perhaps cleaning the gunk out of the distribution block wouldn't be a bad idea.

[Megadan]

How come you used spacers instead of modifying the firewall lip? 

I did modify the lip.  The booster won't sit flush with the firewall because of the center section that holds the pushrod, which is larger in diamter than my stock booster.  It hits the brake pedal bracket and/or the hole the firewall isn't big enough.  Honestly, I would love to ditch the spacers just so the pedal sits higher, but I may have to swap out to a newer XJ brake pedal bracket.

 

 

 

So, this is a longshot, but I've had something similar happen to a friend of mine. Basically, he did everything what you did when installing a new master cylinder. He bench bled it and the bled all the lines in the vehicle. He first used the pump and hold method and used a little vacuum-pump afterwards. He could never get the brakes to work properly after installing the new master. I don't remember the exact symptoms, but there were pressure issues. What turned out to be the culprit was that he pushed the pedal all the way to the floor while doing the pump and hold method. Apparently, in new master cylinders, this can ruin internal seals. Thus causing pressure problems.

 

I never quite believed the story, mostly because it was the guy who sold my buddy the MC who came up with it. But after replacing it with a new one and just using the vacuum-pump, the problem was cured.

 

Other than that, you got enough fluid in the reservoir?

 

Still got the stock prop valve?

 

Perhaps cleaning the gunk out of the distribution block wouldn't be a bad idea.

That may be the case with the master.  I had a buddy doing the pump and hold method and I am pressure sure he pumped it all the way down more than once.  However, I don't see how this can cause the front brakes to drag?  We had the same issue on the used master cylinder as well.  I noticed the weeping when it was installed on the vehicle during the bleeding process.  I can always test this theory and exchange it under warranty and try again.

 

Yes, it is still the stock prop valve and block.   The reservoir is full, and if there was any gunk in the system, it's gone now after pushing half a gallon of fluid through the system.

[Dillithium]

 

That may be the case with the master.  I had a buddy doing the pump and hold method and I am pressure sure he pumped it all the way down more than once.  However, I don't see how this can cause the front brakes to drag?  We had the same issue on the used master cylinder as well.  I noticed the weeping when it was installed on the vehicle during the bleeding process.  I can always test this theory and exchange it under warranty and try again.

 

Yes, it is still the stock prop valve and block.   The reservoir is full, and if there was any gunk in the system, it's gone now after pushing half a gallon of fluid through the system.

 

 

I was pretty stumped by that story too. I could see how the seals could become dislodged and then not allow the pressure to release, thus causing the pads to drag. But that's just my theory after that and your story. It happened a while ago.

 

Personally, I would get rid of the valve in the rear of the truck. It makes bleeding so incredibly difficult. Though it shouldn't have any effect on the front brakes.

How are the new lines you ran from the WJ MC to the distribution block? None are too severely bent are they?

[Megadan]

 

 

That may be the case with the master.  I had a buddy doing the pump and hold method and I am pressure sure he pumped it all the way down more than once.  However, I don't see how this can cause the front brakes to drag?  We had the same issue on the used master cylinder as well.  I noticed the weeping when it was installed on the vehicle during the bleeding process.  I can always test this theory and exchange it under warranty and try again.

 

Yes, it is still the stock prop valve and block.   The reservoir is full, and if there was any gunk in the system, it's gone now after pushing half a gallon of fluid through the system.

 

 

I was pretty stumped by that story too. I could see how the seals could become dislodged and then not allow the pressure to release, thus causing the pads to drag. But that's just my theory after that and your story. It happened a while ago.

 

Personally, I would get rid of the valve in the rear of the truck. It makes bleeding so incredibly difficult. Though it shouldn't have any effect on the front brakes.

How are the new lines you ran from the WJ MC to the distribution block? None are too severely bent are they?

 

Nope, I made nice smooth long bends.  I'm really good with bending, cutting, and flaring tubing.  I normally work with stainless line, which is a lot more of a pain in the butt.  I'm going to go swap out the master cylinder with another and be careful to not push that piston all the way in and see how it goes.

[Megadan]

Took the MC off and sure enough there is a bunch of seal material on the plunger. Going now to get another new one.  Will report back if it makes a difference.

[onlyinajeep726]

If that's an issue with these MC's, that's a $h!##% design...  Got me wanting to check mine now.

[Megadan]

Got the new one, bench bled it, installed it, and was careful to not push it in too far.  Attempted to bleed the rest of the system.  as far as I can tell the funky pressure issue is no more, and it doesn't feel like the fronts are dragging.  Pedal is still super soft and I have to push a lot to stop, so I need to find a way to bleed it more effectively than what I have now.

[cruiser54]

If that's an issue with these MC's, that's a $h!##% design...  Got me wanting to check mine now.

I've had no issues. Easy bleeding also. 

[cruiser54]

Got the new one, bench bled it, installed it, and was careful to not push it in too far.  Attempted to bleed the rest of the system.  as far as I can tell the funky pressure issue is no more, and it doesn't feel like the fronts are dragging.  Pedal is still super soft and I have to push a lot to stop, so I need to find a way to bleed it more effectively than what I have now.

I'm wondering about the booster not going flush with the firewall. That contributes to long pedal travel. 

[Megadan]

 

Got the new one, bench bled it, installed it, and was careful to not push it in too far.  Attempted to bleed the rest of the system.  as far as I can tell the funky pressure issue is no more, and it doesn't feel like the fronts are dragging.  Pedal is still super soft and I have to push a lot to stop, so I need to find a way to bleed it more effectively than what I have now.

I'm wondering about the booster not going flush with the firewall. That contributes to long pedal travel. 

 

If that were the case, then everybody else that has done so would have reported the same problem.  There is pressure immediately when you push on the pedal and you feel the brakes grab, but then the pedal keeps going for 1-2 inches before there is any significant brake force.  Past that point I can actually stop with decent brake force.  I can only assume I have a decent amount of air trapped somewhere, although I have followed the proper bleed procedures.

[cruiser54]

I've never had a problem bleeding the MJ brake system even with the load sensing valve on the back. 

[Dillithium]

Took the MC off and sure enough there is a bunch of seal material on the plunger. Going now to get another new one.  Will report back if it makes a difference.

 

Well son of a b*@$£. I don't like that bleeding it with the pedal all the way down was actually the culprit. But I'm glad all it cost you was some brake fluid.

 

I've never had a problem bleeding the MJ brake system even with the load sensing valve on the back. 

 

I doubt I've bled as many MJ's as you have, but I tried very hard to engage the fifth line to bleed it. I could not get it, after a lot of attempts. I gave up and took it out, braking's better than ever and I don't even have the WJ booster/MC installed yet.

[cruiser54]

 

Took the MC off and sure enough there is a bunch of seal material on the plunger. Going now to get another new one.  Will report back if it makes a difference.

 

Well son of a b*@$£. I don't like that bleeding it with the pedal all the way down was actually the culprit. But I'm glad all it cost you was some brake fluid.

 

I've never had a problem bleeding the MJ brake system even with the load sensing valve on the back. 

 

I doubt I've bled as many MJ's as you have, but I tried very hard to engage the fifth line to bleed it. I could not get it, after a lot of attempts. I gave up and took it out, braking's better than ever and I don't even have the WJ booster/MC installed yet.

 

I wonder if everything would bleed better if the rod was disconnected from the lever on the valve, and then the lever pointed straight up for the duration of the bleeding process. 

[shelbyluvv]

I killed a brand new master on my WJ doing the pump and bleed method. I now do the one pump, hoooooooooollllllllllldddddd and bleed. It seems to work better and does not kill the seals.

[cruiser54]

I killed a brand new master on my WJ doing the pump and bleed method. I now do the one pump, hoooooooooollllllllllldddddd and bleed. It seems to work better and does not kill the seals.

I have to admit I use a MightyVac and bleed them myself. Maybe that's why I've had no issues? 

[Megadan]

Well, I followed the bleed procedures for bench bleeding according to manufacturer instructions, and while I did pump the pedal after install, I only depressed it very slightly a couple of times, and then once a friend opened the bleeder I slowly pushed it down a bit more, but never went beyond halfway.   If I screwed the seals up again, I don't know how.  It seems a bit ridiculous to me that the seals would be THAT weak.

The issue is, the FSM bleeding procedures call for you to fully depress the brake pedal, which is completely counter intuitive to what you are supposed to do with this new MC.

Seems like the only option is to use some sort of power bleeder, but it still doesn't solve getting air out of the bypass system.  Would tying up the valve in the back help?

[Megadan]

I was considering investing in one of these.  I have heard good things about them, and you can get adapters to suit almost any vehicle.  
Admittedly, I do need to do the brakes, and I am pretty sure one of the rear drums is either stuck or way out of adjustment. So that might be part of the pedal issue along with some trapped air.  The problem is, I have to wait until next weekend to really try and get in there and inspect/adjust the rear drums as I am working over 50+ hours all week.

As far as a bleeding system, I may purchase one of these http://www.summitracing.com/parts/mvp-0103?seid=srese1&gclid=CLCM69LOscsCFQuPaQody9QDkgand find a way to get all of the lines open and bled.  Worse case scenario, with that pressurizing the system, I may just crack open the fittings on the lines and see if I can get some air out that way.

On a positive note, with a non leaking booster, my truck is running better than it ever has lol.

[Megadan]

Re-visiting this after making a potential breakthrough in why my brakes act so strange.  While doing my lift I noticed my front pads were pretty thin, so I decided it was time to go over the rest of the brake hardware.  While doing the rear drums, which were all sorts of adjusted horribly, way too tight on the passenger and the drivers side drum nearly fell off in my hands, I realized for the first time that my load sensing valve is completely in the wrong position.  The rod is still there, but after some reading earlier this week I remember seeing something saying that the rod should be around the 3 o'clock position at ride height.  Mine is currently at the 7:30 position, and as the suspension compresses it pushes it in the wrong direction.

Easy enough to fix, but it also has me wondering if the valve even works.  I'm going to  remove the rod and tie it up in maybe a 4 or 5 o'clock position and see if it changes how the brakes feel.  If I feel safe with that, I will connect the rod in the right direction.  I can only assume the same genius that did the brakes the last time on this truck (that means it was all done rather poorly and I had to fix a lot of stuff) also messed with the valve.

I will report back with my findings for closure on this issue.

As a post script, in other news when it rains it pours.  Found my passenger side hub and bearing assembly is on its way out, it has about the same amount of resistance as a properly adjusted drum brake without any brakes on it.  I also discovered the U joint on the axle shaft on that side is starting to make clicking noise and looks pretty dry.  At least I can do one while doing the other.  Already have front bearings on order.

[Minuit]

It goes like this:

 

 

NOT LIKE THIS:

 

The top way is correct. The bottom way gives you almost no rear brakes. Stupid, stupid design and unless you knew exactly what you were doing you might think the bottom way is correct. The prop valve lever shouldn't even be able to go down that far.

[91Pioneer]

 I realized for the first time that my load sensing valve is completely in the wrong position.  The rod is still there, but after some reading earlier this week I remember seeing something saying that the rod should be around the 3 o'clock position at ride height.  Mine is currently at the 7:30 position, and as the suspension compresses it pushes it in the wrong direction.

 

Easy enough to fix, but it also has me wondering if the valve even works.  I'm going to  remove the rod and tie it up in maybe a 4 or 5 o'clock position and see if it changes how the brakes feel.  If I feel safe with that, I will connect the rod in the right direction.  I can only assume the same genius that did the brakes the last time on this truck (that means it was all done rather poorly and I had to fix a lot of stuff) also messed with the valve.

 

Here's a tip. Just use a zip tie to adjust it and do some test stops. This is where I have mine set so the front brakes don't lock up like mad in the winter on slippery roads. I just leave it like that year round and it definitely helped with braking. When I bought the truck the lever was at the 6 o'clock position, bad.

 

Just fix it up and live with it, I beg you. I see too many guys think theirs don't work or they just plain don't understand it so they rip it out. It really is a good idea when operating correctly. Some people just get confused by two lines going to the rear and some mystery valve/rod but it's really simple.

 

I never haul loads so I'm OK with mine being fixed at that level.

 

[schardein]

 While doing the rear drums, which were all sorts of adjusted horribly, way too tight on the passenger and the drivers side drum nearly fell off in my hands, 

Sounds like the self adjusters were installed on the wrong side.  If that is the case, I'd also check that the shoes were correctly installed.  There is a difference.  Primary shoe should be towards the front of the truck, secondary shoe on the rear.  Secondary shoe has more brake lining on it.

 

Shoes are referred to as "leading" and "trailing" in this diagram.  Same as primary and secondary, which you will see in most automotive brake theory:

 

http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Drum_Brake_Service/Drum_Brake_Hardware_10_small.jpg

[gogmorgo]

Stupid, stupid design

IMO it's a beautifully simple way of approaching a somewhat complex and very useful feature. I'll have to post up pics of the crazy setup on my Lada that accomplishes the same thing for comparison.

[Megadan]

It goes like this:

 

 

NOT LIKE THIS:

 

The top way is correct. The bottom way gives you almost no rear brakes. Stupid, stupid design and unless you knew exactly what you were doing you might think the bottom way is correct. The prop valve lever shouldn't even be able to go down that far.

And that bottom picture is exactly how it is currently setup.  That pretty much confirms its wrong. Thanks for the pictures!

 

 

 I realized for the first time that my load sensing valve is completely in the wrong position.  The rod is still there, but after some reading earlier this week I remember seeing something saying that the rod should be around the 3 o'clock position at ride height.  Mine is currently at the 7:30 position, and as the suspension compresses it pushes it in the wrong direction.

 

Easy enough to fix, but it also has me wondering if the valve even works.  I'm going to  remove the rod and tie it up in maybe a 4 or 5 o'clock position and see if it changes how the brakes feel.  If I feel safe with that, I will connect the rod in the right direction.  I can only assume the same genius that did the brakes the last time on this truck (that means it was all done rather poorly and I had to fix a lot of stuff) also messed with the valve.

 

Here's a tip. Just use a zip tie to adjust it and do some test stops. This is where I have mine set so the front brakes don't lock up like mad in the winter on slippery roads. I just leave it like that year round and it definitely helped with braking. When I bought the truck the lever was at the 6 o'clock position, bad.

 

Just fix it up and live with it, I beg you. I see too many guys think theirs don't work or they just plain don't understand it so they rip it out. It really is a good idea when operating correctly. Some people just get confused by two lines going to the rear and some mystery valve/rod but it's really simple.

 

I never haul loads so I'm OK with mine being fixed at that level.

 

 

 

I was going to use zip tiies just to test it and see if it makes a difference, and if so, put it back the way it should be.  I want this valve to function as I do haul loads, and tow a trailer.  

 

 

 

 

 While doing the rear drums, which were all sorts of adjusted horribly, way too tight on the passenger and the drivers side drum nearly fell off in my hands, 

Sounds like the self adjusters were installed on the wrong side.  If that is the case, I'd also check that the shoes were correctly installed.  There is a difference.  Primary shoe should be towards the front of the truck, secondary shoe on the rear.  Secondary shoe has more brake lining on it.

 

Shoes are referred to as "leading" and "trailing" in this diagram.  Same as primary and secondary, which you will see in most automotive brake theory:

 

http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Drum_Brake_Service/Drum_Brake_Hardware_10_small.jpg

 

I think it was installed wrong on the passenger side.  Or at the very least the last person to touch the drums didn't pay attention, because the cable for the adjuster was pinched under the guide instead of resting in it. The drivers side was setup correctly, but not adjusted very well.

 

I replaced the shoes with new ones, and used new hardware.  As far as one shoe having more lining, I did not see this on my new shoes. All 4 had the same part number and thickness.  In the diagram's instance I think they use leading and trailing as names to identify position.  In that case, mine are setup exactly as that diagram shows.

 

I even took the time to install my new parking brake cables that I have had sitting around for over 2 years lol