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Installed Dual diaphram booster: WOW!

djblade311 said:
Check this post:
http://www.naxja.org/forum/showpost.php?p=243390974&postcount=2

1. Check Vacuum at the booster:
1. Start the engine and let it idle.
2. Turn off the engine.
3. Wait a minute or so then pull the vacuum hose with the checkvalve from the booster. Did you hear a vacuum whoosh? If the MC is good, you should still have vacuum in the booster for a long time after turning off the engine.

2. Do you have rear drums or rear disks? If you have drums, make sure the adjusters are put on correctly and not backwards
3. If the pedal is soft when moving only and if you get vibes when braking, check your rotors. If they have deep rings in them, get them resurfaced or new ones.
4. Also check your unit bearings. Loose unit bearings will prevent the calipers from properly seating the brake pad against the rotor and you will run out of compression room from the caliper.

have you bled your brakes correctly:
1. Start from the right rear, then left rear, then right front, and finally left front.
2. pump the pedal until it gets as hard as it can. Usually about 10 times.
3. release the bleeder valve until NOTHING but fluid comes out.

If the pedal doesn't firm up after this, suspect the master cylinder or a leak somewhere. Some say a bad booster will cause a hard pedal with high braking effort, not a low soft pedal.
Click to expand...

Yeah I have done all that. There are no leaks either.
 
gixer said:
Its always been like this. Had the dealer check it when I bought it back in 97 and they said it was fine. Now with a 8,8 in the rear adn 34;s its not good. I need more stoping power. My buddys 98 is the same way. So we are looking for some thing better.
Click to expand...

Really you are going to need to upgrade your whole braking system if running 34's. There is so much extra leverage on the brakes working against you that you need to to get that ratio of tyre to disc size back.
The three way to do this is.
1. WJ brakes and knuckles + new steering.
2. Vanco knuckles with supplied Explorer calipers with Mustang rotors
3. Import the setup I run. www.go.jeep-xj.info/HowtoFordBAdiscs1.htm ;)
 
I am running the 8.8 with disks in the rear. That did help over running the drums. I have gone threw a few front calipers and at first they seemed to be an improvement. ( they were just factory ones ) but then settled in to being just the same. I pulled the rubber stopper out of the proportioning valve. That made the rears work more. I figured I was going to have to start upgrading as the 34’s are only going to last a bit longer before the 38’s get on there. Thanks for the info on some swapping ideas.
 
gixer said:
Yeah I have done all that. There are no leaks either.
Click to expand...

If you did indeed do all of that already, then maybe you should start by replacing the master cylinder with a new one and keep replacing / upgrading everything until the problem is fixed.

if you have a soft brake pedal, that shouldnt have anything to do with your tire size. Tire size and vehicle weight DOES relate to how much effort it takes.
 
gixer said:
Ok know we are getting some where. Booster is fine. Its stops don’t get me wrong but it should stop better than this. I have had a ton of people check the system out mechanics and non mechanincs. When I am told by lets say 12 people that every thing is working correctly then I am going to have to say it is. The pedal is soft not squishy. Its not a hard pedal when you hit it. Maybe I am expecting to much . But I have driven many cars and trucks that the pedal gets hard when hit. Not this rig. My buddy has been threw the same as me with his 98. Also on page 2 Gojeep has a picture on there, my booster looks like the one on the left not the one on the right. Should it look like the one on the right? If so then that’s not what I have.
Click to expand...
If you have the stock rubber lines they may be balooning and absorbing the pressure. If you install some quality steel braided lines, you will have a significant improvement in pedal feel and braking power.
BTW, I too will vouch for cal. He has proven me wrong a time or two, much respect.
 
Well it seems I need to revivie this thread.

I did the booster/MC swap on my 90 XJ. It had ABS (pump was bad) like having manual brakes when you stopped. So I got a booster/MC from a 96 Grand. Booster turned out to be bad (whooshing sound when brake applied), bought new booster. Pedal goes almost to the floor but Jeep does stop. Still don't like it. Got new MC just in case, same problem. Bled everything multiple times, multiple ways, adjuster rear brakes, MC was bench bled prior to installation. I think I have now covered all the basic questions and still I have a pedal that goes almost to the floor.

I am looking for a place to start, I am not much on parts changing just to put new parts on, but if something needs it then all for it. I am trying to get this thing ready for the wife to drive daily so brakes are a good thing

Any ideas chime in please!
 
Are you still running stock calipers and drums? Is the ABS completely removed and replaced with stock non ABS lines and P/valve etc?
 
The ABS has been removed. The lines are the same for either as far as my research has come up with. The prop valve was from a 00 cherokee. I was considering putting the original back in to see what it would do. The ABS system had a prop valve as well.
 
This is an excellent upgrade and I think it's pretty much a must do for anyone with larger tires. I didn't see anyone mention another option. Off Again 4x4 offers a turnkey package. Their Navajo brake kit bolts right up. I have one installed and it's a world of difference.

http://www.offagain4x4.com/Navajo_brakes.html

The only tip is that the replacement master cylinder has the ports reversed from stock. They don't mention that little tidbit and it was fun figuring out why the brakes were so messed up after the swap!
 
my 91 doesn't have a booster because it is some wacky abs system. can i just pull out all the brake components out of the engine bay and leave the lines that go from the engine bay to the brakes, then put in a master clyinder, prop valve and booster in and hook them up to the brake lines that run to the brakes?
 
mitsumotors said:
my 91 doesn't have a booster because it is some wacky abs system. can i just pull out all the brake components out of the engine bay and leave the lines that go from the engine bay to the brakes, then put in a master clyinder, prop valve and booster in and hook them up to the brake lines that run to the brakes?
Click to expand...


Your description was pretty horrible, but yes.
 
Well ended up replacing the calipers, pads and hoses on the front and the drums and shoes on the back. The XJ stops okay now but it sure does have a lot of pedal travel. The brake pedal is about 1 1/2" away from the floor, kinda scary.

I was wondering if I take the 1/4" spacer out from behind the booster that should push the pedal out further and then not so close to the floor when braking. Not that this really needs to be done but it would make me feel better.

Also is there a difference in the pedal assy for the ABS XJs and the non ABS?
The angle on the rod from the booster to the pedal seems to be at a strange double angel up and to the left, did I miss something in doing this upgrade?

Thanks for the help
Chris
 
90% sure the problem is with the pedal assembly and the pedal ratio. The Grand has more rod movement per inch of pedal movement than the XJ. I used a dual diagphram XJ booster with the same vehicles pedal and all was fine. I did hte Grand Booster swap on a friends rig and he had the same problem (good brakes but at the floor) until we put in the pedal box from a dual diagphram XJ which fixed it.

John
 
what is everybody doing about the washer bottle not fitting anymore? swap in a '95+?
 
RickyN29 said:
Hum, I have a 90 and had no issue putting my bottle back.
Click to expand...

Of course your old tank will fit back in if you move it forward about an inch. Using the newer style tank inside the fender is another option if you're looking to free up real estate in the engine compartment. I used the extra space to put in a reel-type GM engine bay light.
 
so to sum this up for me. i have the ABS crap. the optimum set up would be a WJ booster/MC, and a pedal assembly from a non-ABS equipped XJ. that seems to be the most direct, bolt in swap with the least amount of mods needed to make it work.
 
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