[rcgkaw]

First I have 77 cj5 with 360, 4 inches of lift , 33x12.50 mt claws radials. I have what I think is a tj master cylinder and booster. It has a plastic reservoir, and brake lines come out on the drivers side. I bought it off of ebay, the guy said it was from a 93 yj. My dad fabbed up a firewall bracket, put new ends on the brake lines my old cj were of different sizes. I had 4 wheel drums, and the combo worked well for being drums. I just installed front disk brakes with the 1 1/8 rotors and ford stlye calipers with six bolt caliper brackets(Stock for 77-78 cj), new braided extended length hoses 4 inches over stock. We bled only the front brakes after the disk install, probably seven times per side going back and forth. Now my pedal will go to the floor buy pushing it moderately. My dad says it has to be the master cylinder. You can pump the pedal and it will build pressure, but thats not what I expected. My master worked great on the drum set up, then put on the disks and brakes are worse now. My dad also said I may need a vaccum canister off of another vehicle. If it is the master how can tell what year to buy one to replace it, because none of the 5 part stores stock them. Any help on this would be greatly appreciated. Thanks in advance

[jayhawkclint]

You mention it's a TJ unit, but then say it's out of a '93. Not sure it matters; they should be plentiful in either case. Did you check www.napaonline.com? They should have it, and can mail it right to your door.

Sounds like master cylinder to me. I did almost the same upgrade to my drum CJ. Used Chebby 6 bolt caliper brackets and calipers, then '77-'78 CJ rotor.

You might want to consider installing Wilwood 2psi residual pressure valves. You can get them at Summit. They will keep a little pressure on the calipers so that you don't have to double pump. Might even want t consider trying them out before you replace the master cylinder so that you don't go on a wild goose hunt.

[BESRK]

You've got to be careful to match the master cylinder size with wheel cylinder/caliper piston size. If everything is working properly, then it sounds like the master isn't putting out enough volume for the larger caliper pistons. They require much more fluid capacity than a small disk or drum setup. That could be one of the reasons it requires multiple pumps to get the pedal hard. Or... you could have air in the master, the lines, the prop valve or the calipers. You might want to contact Van at http://www.vancopbs.com/ . Yeah.. he sells brake stuff but he's also been a great guy about just giving helpful advise for problems like yours. He's smart about brakes.

[jayhawkclint]

Originally Posted by BESRK

...it sounds like the master isn't putting out enough volume for the larger caliper pistons.

Your results may vary, but I'm running an XJ master cylinder (similar to the YJ master cylinder in most respects) with the same full size caliper setup (1-1/8" rotors) and have had excellent results.

[No_Bs]

Originally Posted by jayhawkclint

Your results may vary, but I'm running an XJ master cylinder (similar to the YJ master cylinder in most respects) with the same full size caliper setup (1-1/8" rotors) and have had excellent results.

How did that work? do you have a pictures of it?

[jayhawkclint]

Originally Posted by No_Bs

do you have a pictures of it?

Mounted master cylinder to firewall with a homemade plate:


Brake pedal mod in progress:


FS Chevy caliper brackets, calipers, hoses, and hardware, '77 Jeep CJ5 1-1/8" rotor mounted to stock JEEP hub: