There are three basic techniques for bleeding brakes: manual, someone pumps while someone else opens & closes the bleeders, pressure bleeding using a device that forces the fluid through the master, lines & calipers under pressure (that's how the factories do it), and vacuum, using a pump to draw the fluid through the system one circuit at a time. Each has it's plusses & minuses. Manual bleeding takes more man power, coordination, etc., and there's the risk on an older vehcle that the master cylinder seals can be damaged by debris in the bores. Pressure bleeding is really effective, but can make a giant mess if the cap on the master cylinder reservoir leaks. Also, it can waste a good bit of unused fluid. It's a technique that's best if you do a lot of vehicles regularly. Vacuum bleeding is fast & efficient, but requires that the bleeders be sealed with something like teflon tape.
Of the three I usually will pressure bleed using a neat small shop tool I got from Motive Power. It's a small pressure bleeder that employs various types of caps for the different master cylinder designs. They have one for the JK that fits & seals perfectly.
A trick I learned from another Forum, you can skip filling the tank with brake fluid and just use air pressure on the system. Top up the reservoir, pump up the Motive Power tank to 15 psi or so, bleed one caliper, check the reservoir level, move on to the next one, etc. Just make sure to stop & top up the master cylinder reservoir periodically. Works like a charm and you won't waste fluid.
The other method I use successfully is vacuum bleeding. There is a new kit on the market specifically for this method, but you can just use a Mighty Vac. Remove each bleed screw and reinstall them sealed with teflon tape to seal the threads. Top up the reservoir, then start at the passenger rear. Install the vacuum pump, pump it up to create a good vaccum & open the bleeder. All the air in the line & caliper will be drawn out first, then the fluid will start to flow. Keep the vaccum up with the pump, draw out a good amount of fluid, then move on to the next. The downside is that the bleeder and vacuum pump line at the nipple will probably seep a bit of air, so you won't know precisely when all the air's out of the system.
FWIW, I experienced this spongy pedal on mine as soon as I replaced the stock rubber lines with braided. The ones I used were good quality (Synergy). I must have pumped a few gallons of fluid through the system, I even took it to the dealer and had them run the ABS routine with the StarScan tool. There just wasn't any air in the system, but the brakes felt spongy and on steep inclines the brakes wouldn't hold the JK in place. Pedal would go all the way to teh stop inside the M/C. Last year I installed Teraflex's Big Brake kit, along with their master and all my braking issues are gone.
Last edited by SoK66; 03-25-2012 at 08:23 AM.