PDA

View Full Version : 9" Rear disk conversion, possible fluid volume problem



JayDee
07-04-2004, 04:37 PM
Well I finished off the 9" disk swap. They're CJ7 front rotors, Cadillac calipers with an integrated parking brake, blah blah blah.

Anyway. I have BLED AND BLED these damn things, the pedal still wants to go to the floor. No air is in the system, and if I clamp off the main rear line, I get front brakes JUST fine. If I clamp both front lines, the rear will clamp HARD but it takes about 1/2 of a pedal travel to start getting there.

My theory is: The Cadillac rear calipers are a "floating" design and when I press the brake pedal I can actually see the caliper move over about 1/16 or 1/8".


SO...

The rear calipers need MORE volume of fluid than my ZJ master cylinder can provide before the pedal hits the floor. Let me know if I'm on the right line here. After looking over Brent's "Kung-Fu Brakes" threads of early and late, I guess my main question would be... what other master cylinders on the market would bolt up to the ZJ booster and offer more fluid volume output?

AND... my Ford D44 front has larger than stock calipers... so that may "use up" a bit more fluid volume as well.

Who's got some input?

http://homepage.mac.com/jaydee59/.Pictures/Photo%20Album%20Pictures/2004-07-04%2012.51.12%20-0700/Image-40BB7C2FCDF311D8.jpg

http://homepage.mac.com/jaydee59/.Pictures/Photo%20Album%20Pictures/2004-07-04%2012.51.12%20-0700/Image-40BB681ECDF311D8.jpg

Alaska ZJ
07-04-2004, 06:19 PM
http://partimages.genpt.com/partimages/53599.jpg

That is a picture of the 98 5.9 ZJ Master Cylinder. The bore is 1.0625. Pitifully small.

Here is the Chevy MC for a whopping 28 bucks.

http://partimages.genpt.com/partimages/34032.jpg

Bore size is 1.31250.....see a difference? That is a big increase in flow. Oh the ZJ MC was over 100 bucks.

Here is the single Diapraph 88XJ booster that will bolt right inplace of your current booster. 77 Bucks with a 20 dollar core.

http://partimages.genpt.com/partimages/91705.jpg

look through Napa online and you might find a MC with better flow that will bolt up to the old double diaphram ZJ booster. In my search I didn't find one.

Enjoy.

JayDee
07-04-2004, 06:26 PM
Is the ZJ booster more powerful than the XJ booster? Would it be possible to swap in an E350 booster as well?

JayDee
07-04-2004, 06:36 PM
From NAPA's website:

Item#: TSM102008
Price: $ 21.99
tax and shipping not included
Core Price: $ 13.00

Attributes:
Attributes: Brake Master Cylinder - Remfd
# of Line Ports: 2
Bore Size: 1.12500'' (what's up with that?)
Line Thread Size: 3/8-24, 7/16-24

nathan
07-04-2004, 09:52 PM
what about the dodge 3500 mc?

Alaska ZJ
07-04-2004, 10:06 PM
JD what MC are those specs for?

JayDee
07-05-2004, 01:44 PM
JD what MC are those specs for?

Those were for a Ford E350. I checked on some 4wd Chevy 1 Ton duallys and they had the bore that you mentioned. The basic mounting looked the same as well.

What sort of trouble would it be to find a booster that is more powerful than the ZJ booster... that a E350 or Chevy 1 ton MC would attach to, AND that would have the correct pedal rod length...? Is that a long shot?

Kraqa
07-05-2004, 03:48 PM
thats really strange cause i have the same rear calipers except i have the duel piston front calipers up front and my stock unit brings my zj to a screeching hault. i can almost lock up 38's doing 50mph. the petal doesn't do much for about the first 1.5" of travel but the rest is all brakes. i will be doing the kung-fu brake set up in the distance futur among other things but for now this works just fine for me. what condition is your master in? i'd check your booster aswell.

JayDee
07-05-2004, 04:15 PM
I think I figured it out. My left rear caliper (brand new) is leaking. I've cranked on the e-brake lever a few times and the right hand caliper is firm (if I clamp off the left rear line). So basically I'm off to buy a new left rear caliper.

BC Broncos better reimburse me for this, too. I'll send them the faulty caliper along with my Autozone reciept.

Ohhhhhhhh the shit we go through, huh? I've got to get this done TO-DAY so I can tow the boat. Front brakes and a clamped rear line really don't cut it when towing.

....and life goes on... :roll:

Troy
07-05-2004, 06:27 PM
Let me know if you continue to have an issue... I've had "volume" related issues ever since installing my front Chevy calipers and rear Lincoln disks on my ZJ. The peddle goes nearly to the floor and at times I get the brake idiot light. But it hold strong and hasn't caused me any issues yet.

I have been told that there's a Corvette master cylinder that can be swapped in. Any truth in that anyone?

Alaska ZJ
07-05-2004, 07:25 PM
Troy, check Napa online. They have the bore size to the MC's they sell.

Get a One Ton Chebby one. 1.25 bore....If that doesn't fix it you gots problems.

chadjans
07-05-2004, 08:28 PM
Are your brake line banjo bolts below the bleader valve?

Chad

BigDaveZJ
07-05-2004, 08:32 PM
Are your brake line banjo bolts below the bleader valve?

Chad

:lookingaroundwonderingwhatkindofidiotwoulddosomet hinglikethat:

BMRisko
07-05-2004, 09:44 PM
Dude! BLEEDERS UP! :twisted:

Alaska ZJ
07-05-2004, 10:21 PM
Dude! BLEEDERS UP! :twisted:

You ain't shittin. I spent 2 months messing with my brakes. My buddy is a ASE Master Mech and my really good friend is a ASE Master Tech who owns his own shop.....Plus the 20+ people in my club that put in thier two bits.

Then one day my Friend says....."hey man, I think these are on upside down" Swap them over and BOOM awesome brakes.....Live and Learn.

JayDee
07-06-2004, 09:32 AM
Dude! BLEEDERS UP! :twisted:

If you KNEW these calipers, you would know that they are mounted at the top, fuckstick! :roll: Jeez, Risko, you do take me as a fool! (don't get too cocky now that you're 21 :D)

Yes, the bleeder IS above the banjo bolt.


I fixed the pedal to the floor problem. Culpret was a leaky piston that would not fully come out of its bore. New caliper fixed it. Now I DO have good stopping power (better than juts fronts for sure) but I don't get any braking power until 1/2 pedal. Trust me... they don't have air.

I'm going to do the Kung Fu upgrade that Brent promotes. I just need to source some cores and I"ll go do it. Finally might pull out that ABS crap too.

JayDee
07-06-2004, 09:38 AM
Brent, do you know if it's possible to mod the factory ZJ booster to accept the chevy or E350 master cylinder? I haven't seen them side by side in person so from your pictures it doesn't look too impossible. What do you think?

What are your thoughts on a residual valve on the rear as well as an adjustable bias valve? I see that Summit has both 2 and 10lb residual valves.... :idea:

Also, would a Grand Waggy booster work? Basically are most boosters going to physically fit the master cyl? I guess the brake pedal rod is another story. Do you know off hand or am I going to need to walk around the junk yard?

Troy
07-06-2004, 12:07 PM
Thought I'd throw this into this thread in case someone doesn't realize that some of the caliper pistons dial in and out...

http://www.hotrodders.com/t22736.html

One of these days I'll get around to looking at my brakes again.

Alaska ZJ
07-06-2004, 12:33 PM
It is probably more work than it is worth to get the ZJ booster to mate to a Chebby or e350 MC.

I looked through the pictures of the Napa catalog and man I just can't find a MC that looks like it will work with the ZJ booster....You might have better luck, let us know if you do.

JayDee
07-06-2004, 04:08 PM
It is probably more work than it is worth to get the ZJ booster to mate to a Chebby or e350 MC.

I looked through the pictures of the Napa catalog and man I just can't find a MC that looks like it will work with the ZJ booster....You might have better luck, let us know if you do.

Well what I'm saying, is that if I did the E350/88 XJ combo, how much power assist will I lose from using that particular booster? I understand it's a bit less powerful just based on size alone, not to mention it's a single diaphragm.

Alaska ZJ
07-06-2004, 04:25 PM
My wife thinks that my brakes are to hard to push. I think they are fine. My brother who is alot smaller than me thinks they are fine but that they are pretty stiff.

It was such an improvement for me that the extra stiffness is not a concern.

I had no problems stopping in any situation if that is what you are worried about. On and offroad.

Troy
07-06-2004, 07:13 PM
Do you think that this banjo to bleeder height difference is enough to matter?

http://smallnet.homeip.net/gallery/albums/Rear-9-Disc-Brakes/DSCF0014.jpg

sweetpea
07-06-2004, 10:16 PM
I have a Ford 9" with the 1978 Lincon Disk brake in the rear of my CJ7.
I 'm using a YJ Booster.
I was having the same problem. it would stop ,but the brake paddle
was almost at the floor.I put in a Master cyl. from a 1978 F150, It did not change much.
I tried the master cylinder from my son's 1990 F250 HD with 460 ci, it have a 1- 1/8" bore.
It worked great , so I bought a new one , solved the problem.
Jean-Guy

Alaska ZJ
07-06-2004, 10:33 PM
Do you think that this banjo to bleeder height difference is enough to matter?

http://smallnet.homeip.net/gallery/albums/Rear-9-Disc-Brakes/DSCF0014.jpg

nope I don't think that is enough to matter.

Alaska ZJ
07-07-2004, 08:47 AM
yea its ok- id really love to see some pics of home made brackets- and lines- i like the idea of mk 7 calipers- non-floating of the mk7 (mark 7) is prefered over the floating caddie design- the cj rotor or the zuki rotor sounds good- so how could i reuse the stock zj rears with the parking prake on these rotors?- if im not mistaken the parking brake in teh stock zj is like an inner drum to the disk? so maybe im better off switching to a caliper with intergrated e-brake- sugjestions?

Moved to here cuz he posted this in a thread about U joints and don't think he meant to.....STOP DRINKING AND POSTING PEOPLE!!!lol

nathan
07-07-2004, 09:47 AM
yea its ok- id really love to see some pics of home made brackets- and lines- i like the idea of mk 7 calipers- non-floating of the mk7 (mark 7) is prefered over the floating caddie design- the cj rotor or the zuki rotor sounds good- so how could i reuse the stock zj rears with the parking prake on these rotors?- if im not mistaken the parking brake in teh stock zj is like an inner drum to the disk? so maybe im better off switching to a caliper with intergrated e-brake- sugjestions?

why would you want to use the zj ebrake when the mark 7 calipers have an internal ebrake?
now that i reread you questions, they make no sense.

use the factory zj calipers with the zj rotors and redrill
or
use mark 7 calipers with suzuki rotors
it's that easy.

luvthejeep
07-07-2004, 11:24 AM
alaska- srry, free labats at my cousins :)

nathan- you answerd the question- thanks :)

luvthejeep
07-08-2004, 01:33 AM
had time to work tonight- got both axles torn down cept for the r&p on the d44- the rear came with a locker! woot woot!- going to go get those calipers tommorow- and some disks- zuki ones- one problem though- the rear came with a nice set of timken berings- one of the races inside of the housing was very loose- it could be spun inside the housing- waht do you guys recomend i do with that? make equal scores around the housing to tigen it up? not shure here- thanks

Kraqa
07-10-2004, 09:05 PM
just a side note. caddy calipers have an E-brake although it doesn't do a damn thing.

i could put my foot on the ground and stop it befor the e-brake would. even with 38's and 3.73 gearing the ebrake still wont hold the jeep in one stop. level ground while in drive. and beleive me they are adjusted i think its faulty cause there is seriously no e-braking.

nathan
07-11-2004, 12:49 AM
just a side note. caddy calipers have an E-brake although it doesn't do a damn thing.

i could put my foot on the ground and stop it befor the e-brake would. even with 38's and 3.73 gearing the ebrake still wont hold the jeep in one stop. level ground while in drive. and beleive me they are adjusted i think its faulty cause there is seriously no e-braking.

are they new/rebuilt calipers or junkyard units? i have heard quite a few bad stories about the ebrake on the caddie units. i haven't hooked up the cables on my lincoln calipers yet to see if they hold.
nathan

JayDee
07-12-2004, 12:58 AM
just a side note. caddy calipers have an E-brake although it doesn't do a damn thing.

i could put my foot on the ground and stop it befor the e-brake would. even with 38's and 3.73 gearing the ebrake still wont hold the jeep in one stop. level ground while in drive. and beleive me they are adjusted i think its faulty cause there is seriously no e-braking.

You have to rotate the piston to fit the rotor size. <ghey>